TRNG I HC BCH KHOA TP H CH MINH

KHOA K THUT A CHT V DU KH

B MN A CHT DU KH

--------

N MN HC TI:

GVHD: Th.S Nguyn Xun Kh

NCS. Trng Quc Thanh

Nhm SVTH: a vt l ng dng

Mc lc

CHNG 1: GII THIU V PHNG PHP AVO ............... Error! Bookmark not defined.

1.1 Lch s pht trin AVO ......................................................................................................... 4

1.2 Tng quan v ng dng phng php AVO ......................................................................... 5

1.2.1 Cc kt qu nghin cu & ng dng phng php AVO trn th gii. .......................... 5

1.2.2 Cc vng v tc gi s dng phng php AVO trong tm kim, thm d du kh ... 6

1.3 Mc tiu, phm vi v ni dung nghin cu v phng php AVO ....................................... 7

1.3.1 Mc tiu nghin cu. ..................................................................................................... 7

1.3.2 Phm vi nghin cu. ....................................................................................................... 7

1.3.3 Ni dung nghin cu ...................................................................................................... 7

1.4 Phng php nghin cu ....................................................................................................... 7

1.5 ngha ca vic nghin cu phng php AVO .................................................................. 8

CHNG 2: C S L THUYT CA PHNG PHP PHN TCH AVO .......................... 9

2.1 Phng trnh Zoeppritz v dng xp x ................................................................................. 9

2.1.1 Hm Zoeppritz .............................................................. Error! Bookmark not defined.

2.1.2 Hm xp x Aki-Richards-Frasier ................................ Error! Bookmark not defined.

2.1.3 Hm xp x Shueys ..................................................... Error! Bookmark not defined.

2.1.4 Hm xp x Hilterman .................................................. Error! Bookmark not defined.

2.1.5 Hm xp x The Fatti et al. ........................................... Error! Bookmark not defined.

2.2 Tnh cht vt l ca nh hng n thuc tnh AVO ..................................................... 16

2.2.1 Thuc tnh vt l c bn ca . .................................................................................. 16

2.2.2 Phng trnh Biot Gassman ...................................................................................... 26

2.3 Phn loi d thng AVO .................................................................................................... 10

2.4 Crossplot AVO Intercept A v Gradient B .......................................................................... 37

2.5 K Thut AVO .................................................................... Error! Bookmark not defined.

CHNG 3: S DNG PHN MM HAMPSON RUSSELL SUITE (HRS) TRONG VIC

PHN TCH V MINH GII AVO ............................................. Error! Bookmark not defined.

3.1 Gii thiu v CGG v phn mm Hampson Russell Suite ............................................... 59

3.1.1 Gii thiu v CGG ....................................................................................................... 59

3.1.2 Gii thiu v phn mm Hampson Russell Suite ...................................................... 60

3.2 Gii thiu v cc modules ca phn mm HRS .................................................................. 61

3.2.1) LithoSI .......................................................................................................................... 61

3.2.2) Pro4D ........................................................................................................................... 62

3.2.3) ProMC ......................................................................................................................... 64

3.2.4) ISMAP ......................................................................................................................... 65

3.2.5) AFI ............................................................................................................................... 65

3.2.6) Geoview ........................................................................................................................ 66

3.2.7) AVO .............................................................................................................................. 67

3.2.8) STRATA (Seismic Inversion) ...................................................................................... 68

3.2.9) EMERGE ...................................................................... Error! Bookmark not defined.

3.2.10) PROAZ ....................................................................................................................... 70

3.2.11) ATTRIBUTES ............................................................................................................ 70

3.3) Workflow phn tch v minh gii AVO .............................................................................. 72

KT LUN V KIN NGH. ....................................................................................................... 77

TI LIU THAM KHO .............................................................................................................. 77

CHNG 1: GII THIU V PHNG PHP AVO Trong nhng nm gn y, vic nng cao hiu qu phng php a chn nhm xc nh cc ch

tiu trc tip tm kim du kh, lm sng t bc tranh c im tng cha du kh rt c ch trng

nh hng n vn mnh ca cc cng ty. Cc cng ngh mi c ch trng n tng phn

gii ca phng php a chn, khai thc trit cc thng tin: bin , tn s, s suy gim nng

lng, khai thc thng tin sng ngang nh nghin cu cc loi thuc tnh a chn (seismic attributes),

nghin cu s thay i bin theo khong cch (AVO), s dng a chn 4C nghin cu sng P v

S, trong s AVO trong nhng nm gn y c s dng rng ri cc nc c k thut thm

d khai thc pht trin nh M, Canada, Nga.. y l phng php tm kim trc tip tm kim trc

tip cc by cha du kh da trn k thut phn tch ti liu a chn trc khi cng (prestack)

AVO hin nay c p dng thnh cng mt s m trn th gii nhng cng c nhiu trng

hp tht bi. Vic nghin cu AVO l mt qu trnh i hi phi c ngun nhn lc c trnh chuyn

mn cao, chi ph cho vic nghin cu ln.

Nghin cu AVO mi trng nc nng ng vai tr thit yu thm lc a Vit Nam v

cc b nc su trong vic nghin cu, xc nh gas hydrates. Tuy nhin VN nghin cu AVO cha

c pht trin mnh m v vic p dng cn tng i hn ch.

1.1 Lch s pht trin AVO

Cc k thut phn tch im sng (bright-spot) v du hiu trc tip xc nh hydrocarbon

pht trin t nhng nm 1970, v sut qung thi gian cc k thut ny c xem l tng i

thnh cng. T cc kt qu cho bin a chn cao, tt l tin c th khoan v khai thc c

hiu qu, v d in hnh l ging khoan thm d tui Creta thung lng Sacramento thuc bang

California (M) cho kt qu ti u. Tuy nhin, khng phi tt c cc im sng u c mi lin h vi

du hiu hydrocarbon. Sut nhng thp k s dng phng php im sng ny, thch thc cho cc

nh a vt l l c th nhn ra du hiu ca hydrocarbon in hnh y l kh trong ct (gas sand)

t mt ct a chn c cng (stacked) thng qua cc d thng vn tc trong cc lp cao hay

thp. Ma thu nm 1974, Chevron cho khoan mt ging - t kt qu thm d trc cho bin cao

- b Fallon thuc Neveda (M) v khi phn tch nhn thy tng ny cho kt qu vn tc cao hn so

vi hydrocarbon. Bill Ostrander sau c ngi ng u Chevron lc by gi l Jim Foster cht

vn tm cch c th phn bit c cc im sng lin quan n hydrocarbon v cc im sng ny

c th kt hp vi kt qu a cht (theo Ostrander nm 2006).

Ostrander lc ch tm nghin cu vn ny, cng vic ca ng dn ng i theo cc

hng khc nhau, t vic nghin cu k cc nh hng khc nhau do hiu ng tuning n vic xem

xt cc phn x nhiu ln vi nng lng truyn ngn (short path multiples) kt hp vi lp mng

cng nh mi lin h gia lp no cho kt qu vn tc thp, vn tc cao. Nm 1975, Ostrander tnh

c tham kho quan im kt qu nghin cu ca Koefoed nm 1955 v nh hng ca t s Poisson

trong h s phn x ca sng phng (plane wave). T s Poisson nh hng trc tip n vn tc sng

P v sng S. ng thi, cng trong thi gian Don Thampson ( thuc nhm nghin cu Chevron)

La Habra, bang California cng nh gi s thay i ca sng P, sng S trong mi trng trm tch,

v tm ra cc d thng trong ct cha kh. S thay th ca nc mn (brine) vi kh trong ct kt c

vn tc cao (high velocity sandstones) gy ra bi sng P, tri li sng S thay i khng ng k. V

th, Thomspon nhn ra c ct cha kh c t s Poisson thp v st c gi tr cao hn nhiu.

Ostrander gi cho Thamspon mu ct tui Creta v st t thung lng Sacramento nh gi vn

tc ca n, hin tng tng t c tm ra. Ostrander tip tc kt hp nhng g tm c t cc kt

qu ca Koefoed i n kt lun rng phn x a chn c th cho thy c cc d thng bin

khi thay i gc ti hoc thay i khong cch.

Ostrander t gi thuyt kim tra tnh ng n ca cc th nghim. Kt qu n tng m

Ostrander t c l pht hin c m kh Putal Sink lin quan n cc im sng (pht hin bi

cng ty Shell nm 1972). Chevron sau mua li cc d liu a chn nm 1973. Vi ci nhn ban

u, tp hp im su chung (CDP gathers) cc m cho kt qu l bin thay i theo khong

cch khng ng k. X l v hin th bin tht (true amplitude) l iu cn thit phi lm,

Ostrander nghin cu v thnh cng trong vic to cc bc x l m vic x l duy tr tnh

tng i ca bin . Kt qu cui cng l tp hp cc mch ghi im su chung m n thay i theo

khong cch theo ng nh gi thuyt a ra. ng thi, ng cng a ra c cc kt qu tt hn

khi ci thin c t s S/N bng cch gim nhiu (cng cc bin nh gn nhau trong mt ct CDP).

Cc kt qu tng t quan st c t cc m t thung lng Sacramento, Vnh Mexico. V th, ln

u tin Ostrander gii thiu tng gi tr ca mnh v a chn AVO nhn bit im sng ni

c hydrocarbon. Nm 1976, Chevron khoan ging u tin da trn thuyt AVO ca Ostrander v cho

kt qu hn mong i

Ostrander cho rng vi iu kin a cht thch hp, kh trong ct c th c hin th trn mt

ct a chn vi s tng bin theo khong cch.

Nm 1976, Andre Romanelli Rosa, sinh vin ca Fred Hilterman i Hc Houston, hon thnh

lun vn thc s vi ti Nghch o AVO (mc d n khng c khuyn khch thi im )

v nghin cu v c tnh ca lm tng tnh thit thc ca gi thuyt nghc o ca mnh. Vi

s nghin cu c lp ca mnh, Rosa ch ra nhng g cn thit lm tng tnh chnh xc khi

nghch o bao gm cc tng nh phn x PP, PS v kt hp bin ti hn trc v bin ti

hn sau (F. Hilterman -2009).

1.2 Tng quan v ng dng phng php AVO

1.2.1 Cc kt qu nghin cu & ng dng phng php AVO trn th gii.

tng nghin cu bin bin i theo khong cch (AVO) c Koefoed gii thiu t nm 1955 vi cu ni ni ting Hon ton c th phc tho ra c tnh cht thch hc chnh xc nu bn nhn vo bin ca sng phn x. Tuy nhin do nhng hn ch v cng ngh nn khng a vo thc t. T nhng nm 1980, cng ty du kh Chevron mi bc u p dng phng php ny v tip mt s tc gi khc tip tc pht trin chng: Castagna (1993), Chaco (1989), Hall (1995), Juhlin (1993), Pedy (1995), Ross (1995)

Trong nhng nm gn y, cc nghin cu v AVO cng dn pht trin v hon thin. Da trn

phng trnh sng phn x ca Zoeppritz (1902), c nhiu phng trnh xp x nghin cu s thay

i bin sng theo cc thuc tnh ca mi trng, cng nh gc ti ca sng. Cc kt qu c ch

ra rng cc mt ranh gii phn x c tr sng m hc v h s Poisson khc nhau s dn ti s thay

i bin khi quan st nhng khong cch khc nhau.

Cc phng php AVO hin ti c ng dng cho cc b trm tch c thnh phn thch hc

khc nhau. Mc ch ca phn tch v minh gii AVO l nghin cu s thay i tn hiu bin lin

quan n s thay i cht lu v khung khc nhau, gip nng cao hiu qu pht hin trc tip du

hiu du kh (DHI) t lt ct a chn. Chacko (1989) a ra mt v d v s dng AVO xc

nh rng b trm tch Nam Sumatra, tc gi tm ra cc tng vi c rng v cht st

khc nhau c tn hiu AVO khc nhau.

Nm 1989, khi nghin cu Hydrocarbon trong lp ct kp st, Rutherford v William s dng

phn tch crossplot (Gradient intercept) phn loi d thng AVO gm 3 loi chnh (AVO class I,

AVO class II v AVO class III), Castagna v Swan (1997) tip tc a ra mt loi d thng AVO

(class IV) mi lin quan vi AVO loi III. M hnh phn loi ny c xem l mu mc v c

s dng rng ri trong phn tch m minh gii d thng AVO hin nay.

Vic s dng k thut phn tch crossplot i khi s khng th cho cc pht hin d thng AVO

r rng c bit khi d liu b nhiu qu nhiu. khc phc iu ny, Castagna v Keho (2000)

ra k thut phn tch Hodogram (phn cc AVO), phng php ny cho ra d thng AVO r rng

hn, khc phc c nhng hn ch m Crossplot mc phi.

Rutherford (2009) s dng phn tch AVO m rng trong cc d n thm d v pht trin,

mc d trc y AVO ch dng trong thm d. Nhng ng dng ng nh v AVO cho Rutherford

phi k n l: m Alpine Alaska, l Jabung (Indonesia), b Ordos v b Sichuan (Trung Quc), Bin

ng Vit Nam, Vnh Mexico (Nghin cu thm v tui Miocene)

Nm 1995, F. Hilterman cng hip hi pht trin a Vt L (GDC) khm ph ra cc Play

Tam vnh Mexico cho tn hiu AVO loi II, loi thng kh pht hin, kt qu cho thy tn hiu

Hydrocarbon ln gp 10 ln tn hiu ca ct bo ha nc.

Vic ng dng AVO trong thm d, tm kim du kh Vit Nam vn cn cha c ng dng

rng ri. Cc nghin cu d thng AVO lin quan n cha kh trong trm tch Miocen c thc

hin trn mt s cu to m Hi Thch (b Nam Cn Sn) vi d thng AVO loi II/III.

AVO l mt k thut phc tp, nu khng thc s sn sng u t thi gian v nhn lc th

khng nn s dng. Khi s dng AVO, chng ta hon ton c th xc nh c trc tip i cha

du, kh, xc nh thnh phn thch hc, rng, p sut l rng thng qua cc thuc tnh vt l

vs dng cc k thut phn tch nh xy dng m hnh, biu crossplot (Intercept, Gradient, Vp/Vs,

PR, NI) hay Hodogram qua , gip gim thiu nhiu ri ro trong thm d cng nh khai thc.

Cng vi s pht trin ca k thut, trong khi l thuyt AVO ngy cng dn hon thin, th nhng

ng dng thc tin cng nh nhng hn ch ca phng php vn ang pht trin v dn khc phc

1.2.2 Cc vng s dng phng php AVO trong tm kim, thm d du kh

Mt s vng trn th gii ng dng thnh cng AVO trong vic pht hin kh nh:

Thung lng Sacramento (Ostrander, 1984; Gassaway, 1984; Soroka et al, 1990), khi

Soroka et.al (1990) khng nh 90% t l thnh cng vi m hnh 3D-AVO vng thung

lng Sacramento v Gassaway (1984) thnh cng trong vic d on cc m cha du

kh vi t l thnh cng cao (13/15)

Vng Bin Bc (Wrolstad, 1986; Snyder et.al, 1989; Strudley, 1990)

Vng Vnh (Zilik, 1989; Hoopes and Alber, 1989; Burnet, 1989 v 1990; Rutherford v

Williams, 1989)

Ngoi khi vnh Mexico (Ostrander, 1984; Rutherford v Williams, 1989; Zimmerman v

Fahmy,1989)

B Arkoma (Rutherford v Williams, 1989)

Vng Ty (Chiburis, 1984; 1987): Du hiu gas trong cacbonate (1987)

Alasca (Zimmerman v Fahmy, 1990)

Italy (Mazzotti, 1990)

1.3 Mc tiu, phm vi v ni dung nghin cu v phng php AVO

1.3.1 Mc tiu nghin cu.

Tm hiu ti liu tng quan v minh gii, phn tch AVO (AVO interpretation and Analysis) v

nhng ng dng AVO trong tm kim thm d du kh

nh gi cc yu t nh hng n qu trnh phn tch AVO nh s thay th cht lu, tnh cht

vt l ca ..

1.3.2 Phm vi nghin cu.

D liu a chn minh gii AVO Canada dng ging dy c km theo theo phn mm

Hampson Russell Suite.

1.3.3 Ni dung nghin cu

Tm hiu tng quan v phng php AVO v ng dng trong xc nh tng cha du kh

Tm hiu v tip cn s dng phn mm Hampson - Russel; p dng trn d liu thc.

1.4 Phng php nghin cu

Thu thp ti liu (gio trnh, sch tham kho) lin quan n l thuyt c bn v nghin cu

AVO. Qua nh gi mi tng quan gia thng s a cht v cc gi tr lin quan trong AVO.

Thu thp cc bi bo, tp ch v cc cng trnh nghin cu v AVO cc nc c nn khoa hc k

thut du kh cao nh M, Canada, Trung Quc, cc tp ch uy tnh nht trn th gii v a cht

a vt l: Hip Hi cc K S a Cht Du Kh Hoa K (American Association Petroleum

Geologists - AAPG), Hip Hi a Vt L Thm D(Society of Exploration Geologists -SEG),

Hip Hi Cc K S Khoa Hc Tri t Chu u (European Associtation Geosciencetists

Engineers - EAGE) , Hip Hi a Vt L Thm D Canada (Canadaian Society of Exploration

Geologists - CSEG) cng nh cc n phm sch t trong nc: Tp ch Du Kh, i Hc Quc

Gia TPHCM, i Hc M a Cht H Ni, nc ngoi nh: Springer, Cambridge, Taylor Francis,

Geoscience World lin quan n cc kt qu minh gii AVO v vic nh gi trin vng du kh

Tm hiu s dng phn mm Hampson Russell Suite ca tp on CGG vi cc cng c

x l, minh gii v phn tch cc thuc tnh a chn v m t c im tng cha t cc d liu

(data sample training) bao gm: d liu a chn v d liu welllog nh km trong phn mm,

v cc hng dn lin quan n vic s dng phn mm c ly t website CGG.com.

1.5 ngha ca vic nghin cu phng php AVO

Kt qu nghin cu l ti liu hu ch cho nghin cu v ng dng AVO trong tm kim thm d du kh nht l vng nc su v tm kim gas hydrate.

Cho thy vai tr quan trng ca AVO trong minh gii ti liu a chn, h tr cng tc tm

kim thm d du kh cung cp v d thc t v ti , hng dn cc bc minh gii, trnh by

tng quan k thut minh gii vi i tng thc t v nh gi tin cy ca vic minh gii. To

tin cho cc sinh vin tm hiu su hn v c th pht trin hng nghin cu mi, t m ra

cho sinh vin cc c hi pht trin kin thc cng nh ngh nghip sau ny

CHNG 2: C S L THUYT CA PHNG PHP PHN TCH

AVO

2.1 Phng trnh Zoeppritz v dng xp x

Khi sng P ti mt ranh gii gia hai mi trng, sng chia thnh cc thnh phn sng phn x

v khc x P, ng thi cng to ra sng th cp phn x v khc x S (Hnh 2.1). Cc thnh phn

sng ny lan truyn tun theo nh lut Snell.

Khi sng ti P vung gc vi mt ranh gii, cc h s phn x (R) v h s truyn (T) qua l hng

s v c xc nh:

21

120

II

IIR

v

21

10

2

II

IT

Trong : vI : c gi l tr sng m hc ca mi trng.

Tuy nhin, khi gc ti ca sng khc khng ( 01 ), h s phn x ca sng khng cn l hng

s m s thay i theo gc ti ca sng, hay bin thay i theo khong cch thu n. Nghin cu s

thay i bin theo khong cch thu n (hay gc ti ca sng) c gi l l phng php AVO

(Amplitude versus Offset). H s phn x, cng nh h s truyn qua l mt hm ph thuc vo gc

ti v cc tnh cht n hi ca mi trng, gm: mt , modun khi v modun ct.

Phng trnh Zoeppritz xc nh cc h s phn x v h s truyn qua cho sng phng, l hm

4 n ca gc ti v ca ba thng s n hi c lp trn mi b mt.

Phng trnh Zoeppritz cho kt qu chnh xc cc gi tr bin ca sng. Nhng kh phc tp

v li gii mt thi gian, v vy chng khng h tr mt cch trc quan hiu v mi lin quan gia

bin khc nhau n tham s n hi nh th no hoc s bin i ca tham s nh hng nh th

no n cc ng cong h s phn x. Trong thi gian qua, nhiu phng trnh Zoeppritz xp x

c thit k cung cp thng s m t hnh vi ca bin .

(2.)

2.2 Phn loi d thng AVO

Rutherford v Williams (1989) xut mt h thng phn loi AVO cho ct cha kh da

trn h s phn x gc P. Ri Castagna et al. (1998) m rng h thng phn loi Rutherford v

Williams trn c s nc tng ct cha kh nm trong biu crossplot Intercept Gradient (Bng

2.2.1). Biu crossplot ny c chia thnh bn gc phn t, xc nh bi tn hiu Intercept v tn

hiu Gradient (Hnh 2.2.1).

Bng 2.2.1: c trng ca cc loi AVO da trn v tr ca chng trn biu crossplot thuc tnh

intercept (P) gradient (G), v tn hiu ca chng lin quan vi cc thuc tnh trn. (Bng 1: Trang

128 sch AVO Satinder Chopra v John P. Castagna, 2014)

Loi (Class)

khng tng i (Relative impedance) Gc phn t (Quadrant)

Intercept

(P)

Gradient

(G)

1 Ct c khng cao IV + -

2n khng tng phn gn bng 0 III - -

2p khng tng phn gn bng 0 IV + -

3 Ct c khng thp III - -

4 Ct c khng thp II - +

Hnh 2.2.1: Biu crossplot intercept-gradient, cho thy bn gc phn t c th (I-IV). Biu

ca s thi gian gii hn, time-window (biu crossplot th hin cc tn hiu ti nhiu

su), ct kt bo ha nc v st c xu hng nm dc theo ng c s (background trend).

nh phn x nc tng ct cha kh c xu hng nm di background trend, trong khi y

phn x ca ct cha kh c xu hng nm trn background trend. Trong Rutherford v

Williams (1989) loi ct cha kh cng l i tng c nghin cu. Ch rng s La M

(Roman) y (I-IV) cng tng ng ch s Rp (Arabic) (1-4) trong n ny. Hnh 6 ca

bi bo Castagna et al. (1998) v hnh 7 ca AVO Satinder Chopra v John P. Castagna,

(2014).

D thng AVO loi 1.

c mt v d ca mt ct AVO loi 1, chng ta s xem st ct c khng cao c bao

trong st. H s phn x ca loi ct ny dng ti gc ti 0 (zero offset) (tc, c Intercept dng) v

gim dn khi tng gc ti (c gradient m). ln phn x ca ct loi 1 c th thay i cc khi

trong mt di gc ti hoc mt di khong cch thu n no . Bi v s o cc, phn x phn

hi c th bng gi tr trong cng CMP (CMP stack), nn hiu ng im ti (dim-spot) c th c

thy trong d liu a chn cng (stack). Ti mt di su, thnh h cng ct c kt tt vi t s

Vp/Vs thp so vi xung quanh biu th l d thng AVO loi I. trong hnh 2.2.2a chng ta thy

m hnh phn x AVO cho loi I ct cha kh Bluesky t Alberta, Canada. Vi AVO loi 1, ch

rng bin gim khi tng khong cch thu n.

D thng AVO loi 2.

Mt loi ct loi 2 c khng m thp (mt gi tr intercept thp) v c gi tr Gradient m mnh.

Loi ct ny thng kh c th d on khi c s xut hin ca nhiu v c th xut hin nh l mt

im ti, im sng hoc o cc trong d liu cng a chn (stack). Cc d thng AVO loi 2

thng c thy trong cc trm tch c kt v nn va phi. Ross v Kinman (1995) xut phn

bit gia d thng loi 2p v loi 2n, vi loi th nht (2p)c intercept dng v gradient m, do

gy nn s o cc khi khong cch thu n tng, loi kia (2n) th li c intercept m v gradient m

(v do khng c s o cc). Hnh 2.2.2b cho thy h hnh phn x ca ct channel Mannville t

Alberta, Canada. Vi AVO loi 2, ch s tng y bin (nhn bit bi mi tn mu xanh lam).

D thng AVO loi 3.

Ct loi 3 c khng thp hn so vi cc loi ct trung bnh v l loi ct im sng lin quan ti

cc d thng bin trong mt ct cng (stack section). N c intercept m, gradient m v th hin

phn x cao ti tt c cc khong cch thu n. c bit, cc trm tch cha c kt nng tng i

cho thy d thng loi 3. Hnh 2.2.2c cho thy m hnh phn hi vi loi ct cha kh loi 3 t Ty

M. Vi AVO loi 3, ch bin m lin quan ti nc tng cha; n tr nn m dn khi khong

cch thu n tng.

D thng AVO loi 4.

Castagna v Swan (1997) m rng h thng phn loi ca Rutherford v Williams (1989) a

vo ct AVO loi 4. Mt bin ln v m c th hin bi loi ct ny ti gc ti bng 0 v ri

tng nh khi khong cch thu n tng. Loi d thng ny c th c tm thy cc ct nng, rt

cha c kt hoc ct mm thy di m cng (hard cap rocks) nh l st cng, siltstone, hoc l

carbonat.

Hnh 2.2.2d cho thy mt m hnh phn x AVO cho ct cha kh loi 4 t ty M. Ch rng ti

im gc ti khng ct cha kh th hin bin m v bin cng tr nn t m khi tng khong

cch thu n. Trong 2.2.(3b, 4, 5, v 6) th hin d thng loi 1, 2, 3 v 4, lin quan ti d liu a

chn thc. Nhng d thng a chn thc ny c th so snh vi m hnh phn hi hnh 2.2.2.

Hnh 2.2.2: M hnh phn hi a chn cho mt tp thng s ly t well log vi (a) AVO

loi 1, (b) loi 2, (c) loi 3, v (d) loi 4. Phn hi a chn c phn loi theo c s phn loi

ca Rutherford v Williams (1989) (AVO Satinder Chopra v John P. Castagna, (2014))

Hnh 2.2.3: So snh m hnh v gi d liu thc. (a) Mt gi tng hp (Synthetic stack) cho

thy phn hi ct cha kh AVO loi 1, (b) mt gi d liu a chn thc t t mt ging, v

(c) mt gi vi phn hi ct t. (Hnh 2 nm trong AVO Satinder Chopra v John P.

Castagna, (2014) chng 6 da trn hnh 1.15 ca Downton (2005))

Hnh 2.2.4: V d ca AVO loi 2 ti su 2.1 km, trong mt gi CMP ca d liu m.

Nhng s kin vi cc c t en. (Hnh 9 nm trong AVO Satinder Chopra v John P.

Castagna, (2014) chng 6 da trn hnh 1 ca Tura v Rowbotham)

Hnh 2.2.5: (a) Mt gi x l th

hin ng ng mc 30o v 60o,

bc l hai loi s kin ct cha kh

(1 v 3); st hu c c thy 2.

(Hnh 10a nm trong AVO

Satinder Chopra v John P.

Castagna, (2014) chng 6 da

trn hnh 3 ca Leaney v hope

(1998).

(b) gi x l t nc su, ngoi

bin b bin Ty n , cho thy

loi 3 lin quan ti kh tp trung

di nn vng n nh Hydrat c

trng bi phn x m phng y.

(Hnh 10b nm trong AVO

Satinder Chopra v John P.

Castagna, (2014) chng 6 da

trn hnh 2 ca Chaudhuri et al.

(2002))

Hnh 2.2.6: Gi m hnh s dng 3 phng php khc nhau v cho thy vng mc tiu trong 3

ging khc nhau: ging E, D, v A. cc gi c dng (a) phng trnh Zoeppritz, (b) phng

trnh sng n hi, bao gm sng phn x v chuyn qua nhng khng c sng phn x nhiu

ln, v (c) phng trnh sng n hi. Trong mi trng hp gi m hnh c so snh vi d

liu thc trong (d). Ricker wavelet vi tn s trung tm l 40 Hz v mt di tn s t 6-80 Hz

c s dng trong vic m hnh. Cc d thng trong vng quan tm l ct loi 4. (Hnh 11

nm trong AVO Satinder Chopra v John P. Castagna, (2014) chng 6 da trn hnh4 ca

Xue et al. (2007))

2.3 Tnh cht vt l ca nh hng n thuc tnh AVO

2.3.1 Thuc tnh vt l c bn ca .

- Mt

- P- v S- wave

- Phng trnh vn tc

- T s Poisson.

Thuc tnh AVO ph thuc vo vn tc ca sng dc (Vp), vn tc sng ngang (Vs) cng nh

mt ca (b). xy dng m hnh a chn tng hp, cn phi c d liu vn tc v mt

ch yu ly t ti liu VL ging khoan. Vic tnh ton h s phn x theo khong cch thu n yu

cu phi c 2 loi vn tc sng trn cng nh b . Hnh 2.3.1 minh ha c trng ca mt phng sng

dc (sng P) v sng ngang (sng S) lan truyn trong mi trng n hi. Sng dc c phng dao

ng ca phn t trng vi phng truyn sng, khi cc phn t dao ng vung gc vi phng

truyn sng th s xut hin sng ngang. Do sng P s b nh hng nhiu hn sng S khi truyn

trong cc tp ct cha kh. Vn tc sng a chn l mt hm ph thuc vo thi gian v lin quan

n s bin dng n hi ca . S lan truyn ca sng P lm cho khi b nn p v thay i th

tch, trong khi sng S ch gy ra bin dng trt (shear) m khng lm thay i th tch ca (Hnh

2.3.2)

Hnh 2.3.1: M phng sng dc (P) v sng ngang (S)

a) Sng P b) Sng S

Mt khi ca (b) l khi lng ca mt n v th tch iu kin va v c tnh

da vo trung bnh trng s cc thnh phn mt trong (Hnh 2.3.3):

mfl

mb

Trong : : rng ca

b : Mt khi ca

m : Mt thnh phn thch hc ca ca khung (matrix)

fl : Mt ca cht lu trong l rng.

Rock matrix

(m)

Pores/fluid

Hnh 2.3.3: Cc thnh phn mt

ca vi rng gia cc ht

Hnh 2.3.2: Bin dng ca i vi sng a chn

VS Thay i

hnh dng

VP Thay i hnh

dng & th tch

(2.3.1)

Khi trong l rng cng tn ti nhiu loi cht lu (nc v Hydrocacbon), gi tr fl c tnh

n gin theo trung bnh trng s ca tng thnh phn mt cht lu v ph thuc vo bo ha

tng loi cht lu:

)1( wHCwwfl SS ,

Vi wHCw S,, ln lt l mt ca nc, mt Hydrocacbon v bo ha ca nc.

Kt hp phng trnh (2.3.1) v (2.3.2), mt khi ca c cht lu trong l rng xc nh

theo phng trnh sau:

)S(S)( wHCwwmb 11 ,

Gi tr b c xc nh khi l rng bo ha hon ton cht lu c gi l mt khi bo

ha ca ( sat : Saturated density). Cc loi khc nhau c nhng ranh gii vn tc v mt khc

nhau, mi quan h gia mt v vn tc sng P ca mt s loi c th hin trn hnh 2.3.4. Nhn chung, Carbonate c mt khi v mi trng vn tc cao hn cc loi clastic. Mt khi v vn tc truyn sng c mi tng quan dng i vi clastic v carbonate. Do , khi rng tng tng ng tr khng m gim.

Hnh 2.3.4: Mi quan h gia mt

v VP ca mt s loi trm tch

(cha nc mn), da trn d liu ca

Castagna et al (1993).

Sng a chn gy ra bin dng n hi trong mi trng , do vic nghin cu hnh vi ng

x ca l rt quan trng c th nh gi c vn tc v mt . C nhiu thng s n hi

c s dng m t hnh vi bin i n hi v ng hng ca ca . Bng 2.3.1 th hin cc

tham s n hi khc nhau, s dng hai gi tr tham s c lp bit c th tnh c bt k cc tham

s n hi cn li.

Modun n hi l thng s quan trng c trng cho mc bin dng ca di cc ng sut

khc nhau. Khi tnh ton nh hng ca thay i cht lu i vi vn tc v mt (m hnh thay th

(2.3.2)

(2.3.3)

cht lu) th vic tnh ton cc gi tr modun n hi l cn thit trc khi nh gi s thay i vn

tc cng nh mt . M un khi (K) m t bin dng th tch di tc dng ca ng sut php bng

nhau theo mi hng (Hnh 2.3.5a), c xc nh l t s gia ng sut nn th tch S v bin dng

th tch VV / .

VV

SK

/ ,

Modun khi c trng cho kh nng chng li bin dng nn th tch ca , ghch o gi tr

modun khi c gi l nn (C). Modun ct () c trng cho xu hng bin dng ca vi th

tch khng i khi chu tc dng bi ng sut tip v c xc nh l t s gia ng sut tip (shear

stress) v bin dng ko (shear strain):

bin dng ko c o thng qua gc trt gia khi ban u v khi sau khi b bin

dng (Hnh 2.3.5b). Modun ct biu th cng hoc kh nng chng li mc rung lc ca . Hu

ht cc cht lu khng c sc chng ct nn thng gi thit Modun ct ca cht lu bng 0 (fluid=0).

Bn

g 2.3

.3.1: C

c hn

g s

n h

i tro

ng m

i tr

n

g n

g h

n

g (Theo

Smid

t, 20

09).

n

v Mo

du

n: G

pa, V

=km/s,

=g/cc

Hnh 2.3.6: T s Poisson

ng sut tip

Bin dng ko =

ng sut tip

ng sut

php S

(N/m2)

b) a)

Hnh 2.3.5: S thay i hnh dng

v th tch ca di tc dng

ca ng sut; (a) Thay i th tch

vi ng sut php bng nhau t

mi hng, (b) Thay i hnh

dng di tc dng ca ng sut

tip

(2.3.4)

(2.3.5)

Bn

g 2

.3.1

: Cc h

ng s

n

hi tro

ng m

i tr

ng

ng h

ng (T

heo

Sm

idt, 2

009).

n v

Modun: G

Pa, V

=km

/s, =

g/cc

Cc gi tr modun n hi thng khng o trc tip m c tnh thng qua gi tr vn tc v

mt . Trong mi trng ng hng, vn tc sng khng ph thuc vo hng lan truyn. Mi

quan h gia vn tc sng v thuc tnh n hi ca c th hin cc phng trnh sau:

3

4

K

VP hoc

2PV

V

SV

So snh VP v VS ta c: 22

S

P

V

V

Trong : K l Modun khi ( 3

2K )

: Modun ct (hay hng s Lame th 2)

: hng s lame th nht

: mt khi ca

Trong phng php nghin cu AVO, vic nghin cu h s Poisson v mi quan h gia chng

vi cc tham s khc rt quan trng. T s Poisson ( ) l t s gia bin dng ngang tng i v

bin dng trc tng i (Hnh 2.3.6) v c xc nh theo cng thc sau:

)3(2

23

/

/

K

K

ll

ww

S thay i t s Poisson qua b mt ranh gii phn x lm gy ra s thay i bin theo

khong cch thu n. H s Poisson c xc nh trong phng th nghim bng cch o s bin dng

ca vt th khi thay i lc tc dng mt cch t t, nhit khng i (qu trnh ng nhit). Ngoi

thc a, h s Poisson c xc nh thng qu tc truyn sng VP v VS. y l s bin dng do

lc tc ng nhanh ca sng gy ra, khng c s trao i nhit (qu trnh on nhit). T cc phng

trnh (2.3.6), (2.3.7) v (2.3.8), xc nh c s ph thuc h s Poisson v t s VP/VS.

,22

2

vi

2

S

P

V

V

Theo l thuyt, h s poisson c th m. Tuy nhin, theo cng thc trn v t s

2S

P

VV

th hin h gi tr ]5.0;0[ . Cng thc (2.3.9) cng cho thy ng bin vi t

s . Mi quan h chung gia VP/VS v h s Poisson cng vi cc gi tr in hnh ca ct

v st kt cha cc cht lu khc nhau c th hin trn th hnh 2.3.7. Ct kt c gi tr

Poisson thp hn st kt v khong vt thch anh c gi tr Vp/VS thp nht trong cc loi

khong vt khc (Hnh 2.3.8). cha du (c bit kh) c VP thp v VS cao hn bo

ha nc. Do , ct kt cha Hydrocarbon c h s Poisson thp hn ct kt cha nc.

(2.3.6)

(2.3.7)

(2.3.8)

(2.3.9)

Bng 2.3.2: H s Poisson ca mt s loi

Tn Tn

- Than

- Dolomit (c st)

- Dolomit >10%

- vi cht st

- vi >10%

- Ct kt rng

thp

0.4 0.45

0.26 0.29 (0.28)

0.26 0.23

0.29 0.31

0.28 0.35

0.17 0.26

- Ct kt ( >10%)

- Ct kt bo ha kh

( >2% - 5%)

- Ct kt cha gn kt

cha kh ( >2% - 5%)

- St cha vi

- Bt kt

0.22 0.28

0.1 0.24 (0.2)

0.15 0.24

0.23 0.67 (0.67)

0.28 0.33

Hnh 2.3.7: th tng quan gia

h s Poisson v t s VP/VS. Mt s

gi tr in hnh ca h s poisson

phn nh c im mi trng cn

lu :

(cha kh)

(cha nc)

(mi trng

khng kh hoc nc c

fluid=0, VS=0)

H s Poisson ca mt s loi

c th hin bng 2.3.2.

J.Castagna (1985), xc nh thc nghim mi quan h tuyn tnh gia VP v VS trn clastic

bo ha nc mn (brine), theo cng thc sau:

36.116.1 SP VV (km/s)

th ca cng thc (2.3.10) c gi l ng Mudrock (Mudrock line) hay cn gi l ng

thng ARCO (hnh 2.3.9). ng Mudrock c dng nh gi VS trong trng hp khng c d

Hnh 2.3.9: th gc ng Mudrock line ca J.Castagna (1985)

Hnh 2.3.8: Ct kt c gi tr

Poisson thp hn st kt v

khong vt thch anh c gi

tr Vp/VS thp nht trong cc

loi khong vt khc

(2.3.10)

liu vn tc sng ngang. Phng trnh l cng c thc nghim tt cho vic nh gi vn tc sng trn

ct bo ha nc v st kt.

Ch rng vi h s Poisson xc nh, t (2.3.9) ta c: SP VV12

22

. ng thng phng

trnh ny khc vi ng mudrock v khng c h s t do trong phng trnh, vic xc nh cc im

lch khi ng mudrock c th nh gi cho pht hin du hoc kh (Hnh 2.3.10).

Greenberg v Castagna (1992) m rng phng trnh ng Mudrock xc nh i vi cc

loi c thnh phn thch hc khc, biu din VS ph thuc voVP (n v km/s):

Ct kt: PS VV 804.0856.0

vi: 2055.0017.1031.1 PPS VVV

Dolomite: PS VV 583..0078.0

St kt: PS VV 770.0867.0

th hnh 2.3.11, biu din kt qu thc nghim gia VS v VP ca Castagna i vi cc loi

trm tch khc nhau, th cn th hin cc ng ng Poisson.

Nghin cu cc yu t a cht lin quan n h s Poisson, c th rt ra mt s nhn xt:

H s Poisson tng khi thnh phn st, rng (c cha nc bin ho du), p sut

rng v nhit tng

H s Poisson gim khi thnh phn thch anh, rng, p sut c st tng v kh thay ch

du, nc.

Cc kt qu nghin cu cho thy bin bin i theo khong cch vi nhng quy lut khc

nhau ph thuc vo mi quan h ca h s Poisson v tr sng m hc (AI) qua mt ranh gii phn

x. Mi quan h c tm tt bng 2.3.3:

Nu tr sng v h s Poisson tng qua mt ranh gii th bin tng theo khong cch.

Nu tr sng tng, Poisson gim th bin i gim theo khong cch

Hnh 2.3.10: ng mudrock v

cc ng thng ng vi mt gi

tr hng s Poisson

Nu tr sng gim th ty thuc vo h s Poisson tng hoc gim m bin tng i

tng hoc gim v gi tr bin tuyt i bin i theo quy lut ngc li.

Tr sng m hc

(AI)

H s Poisson

( )

Bin

tng i

Bin

tuyt i

Qua bng trn, chng ta c nhn xt l s thay i gi tr tng i ca bin khng ph thuc

vo s thay i tr sng m lun thay i cng chiu vi s thay i h s Poisson. Trong khi , gi

tr tuyt i ca bin s ngc vi s thay i h s Poisson nu tr sng gim qua mt ranh gii.

Mc d nhiu loi thch hc c cng tr sng m hc, tuy nhin chng c h s Poisson khc

nhau r rng (Hnh 2.3.11). Mt vi loi c th phn bit r rng, v d: than c mt khi

thp, h s Poisson cao (Hnh 2.3.4, 2.3.11) v cho tn hiu phn x bin cao ging nh tn hiu t

cc tp c cha kh. Tuy nhin, than c xu hng cho tn hiu AVO loi IV, trong khi ct cha kh

hnh thnh AVO loi III. Da vo s khc bit ny c th phn bit r rng than v cc tp ct cha

kh.

Bng 2.3.3: Quy lut AVO theo AI v H s Poisson

VP (km/s)

VS

(km

/s)

Coal

Sandstone

Limestone

Dolomite

Anhydrite

Shale

Salt

Hnh 2.3.11: Mi quan h VP v VS

ca mt s loi trm tch (cha

nc mn da trn phng trnh thc

nghim vn tc sng ca Greenberg

v Castagna (d liu ca

Castagna,1993). ng nt nt l cc

ng ng h s Poisson.

H s Poisson ca clastic v carbonate cng c xu hng kh khc nhau. Ct kt v st

kt c h s Poisson gim khi rng gim (AI cao). Trong khi , h s Poisson ca vi v

dolomite c xu hng khng i khi rng gim ( th gn nh nm ngang, hnh 2.3.11). Do vy,

cn phi thn trng khi p dng cc quy lut chung ca vt l clastic i vi trm tch carbonate.

2.3.2 Phng trnh Biot Gassman

- Gii thiu.

- Gi thit

- Thay th cht lu.

Modun n hi ca c cht lu v kh (khng cha cht lu) rt khc nhau. th hnh

2.3.13 th hin gi tr o modun K v modun trong phng th nghim ca mu ct rng cao, cha

c kt. Kt qu cho thy, s khc bit gi tr modun khi K gia kh v bo ha nc l rt ln.

Trong khi , gi tr modun ct khng i.

Mt trong nhng vn quan trng nht khi phn tch vt l trn cc ti liu log, mu li

v a chn l s dng vn tc sng a chn trn bo ha cht lu d on cho bo ha

mt loi cht lu khc, hoc d on vn tc trong bo ha t vn tc lan truyn trong kh v

ngc li. Vn ny c gi l s thay th cht lu (fluid substitution).

Nh cp mc 2.3.1, khi sng a chn lan truyn qua khi , n to ra mt ti trng

ng tc dng ln khi , lm cho khi c xu hng bin dng v thay i th tch (sng P lan

truyn), ng thi lm gia tng p sut l rng chng li s nn p ca ti trng ng gy ra, lm cng

H

s

Po

isso

n

rng

Tr sng m (km/s.g/cc)

Hnh 2.3.12: Quan h gia h s

Poisson v tr sng m ca mt s

loi trm tch thng thng (cha

nc mn), da trn d liu ca

Castagna et al (1993).

khi hn. Do , modun khi hiu dng Ksat ca bo ha tng ln hn so vi modun khi K ca

kh.

Biot (1941) v Gassmann (1951) pht trin c lp l thuyt lan truyn sng trong bo

ha cht lu, c bit l trong tp ct cha kh, xc nh mi quan h gia modun n hi v vn tc

sng trong bo ha da trn phng trnh thng thng (2.3.6) v (2.3.7):

sat

satsatsat

P

K

V

3

4

sat

satsat

SV

Biot v Gassmann a ra phng trnh l thuyt thay th cht lu, bng vic xc nh phng

trnh quan h gia modun khi ca bo ha v modun khi ca kh. Theo , Ksat ph thuc

vo rng v cc thnh phn modun khc nhau trong (Hnh 2.3.3.14):

2

2

1

)1(

m

dry

mfl

m

dry

drysat

K

K

KK

K

K

KK

, drysat

Trong :

- Kdry: modun khi ca kh

v

Hnh 2.3.13: Quan h modun khi (a) v modun ct (b) vi p sut a tnh ca ct cha c kt,

rng cao. p sut l rng khng i (=0.1Mpa). D liu trn mu bo ha nc c th nghim

bng sng siu m. (D liu ca Zimmer, 2003)

(2.3.11)

(2.3.12)

- Km: modun khi ca khong vt to nn (m=rock matrix)

- Kfl: modun khi ca cht lu trong l lng

- : rng ca .

- sat v dry ln lt l modun ct ca bo ha v kh. Trong phng trnh

Biot Gassmann, gi tr modun ct khng i khi bo ha cht lu thay i,

vi gi tr rng l hng s.

Mavko (1995) sp xp li phng trnh trn v a ra dng phng trnh mi trc quan hn:

)( flm

fl

drym

dry

satm

sat

KK

K

KK

K

KK

K

T (2.3.6) v (2.3.7), gi tr modun khi c th xc nh c nu c vn tc VP v VS bng mi

quan h: 22

3

4SP VVK . Tuy nhin, d liu vn tc sng S i khi khng c hoc khng ng tin

cy, do khng th nh gi c modun khi. Gregory (1977) xut s dng modun nn p (M:

Compressional modulus) thay cho modun khi da trn vn tc sng P, phng trnh (2.) c vit

li:

2

2

1

)1(

m

dry

mfl

m

dry

drysat

K

K

KK

K

K

MM

Hnh 2.3.14: Cc thnh phn c bn trong khi nh hng n Ksat

(2.3.14)

(2.3.15)

Trong : 3

42 satPsat KVM

drydrydry KSKM .3/4 vi )1(

)1(3

dry

dryS

Bin i i s phng trnh (2.) a v dng ton phng bc 2 v c th xc nh c modun

khi ca kh Kdry.

02 cba Cc tham s trong phng trnh trn c xc nh nh di y:

- :1m

drydry

dry

p

K

K

K

K

V

v

gi l h s Biot, c trng cho t s thay i th tch l

rng i vi thay i th tch khi. Gii phng trnh bc 2 theo , t xc nh c

1mdry KK . - ,1 Sa

- m

sat

fl

m

K

MS

K

KSb

1.

-

1

fl

m

m

sat

K

K

K

MSc

Phng trnh Biot Gassmann ch c p dng da trn cc gi thit sau:

(a) phi ng nht v n hi ng hng

(b) Cc khong vt trong phi c cng gi tr modun khi, modun ct v mt

(c) Cht lu phi lp y l rng v c mi quan h thy lc tt. iu ny c ngha rng, cht

lu c th di chuyn t do qua cc l rng v lm trit tiu ng sut gia tng l rng nu

c bt k s dao ng p sut l rng. Tuy nhin, hnh dng l rng c th l bt k.

(d) Sng lan truyn vi tn s thp p sut l rng c cn bng trong ton b l rng.

Phng trnh Biot-Gassmann ng dng tt nht cho d liu a chn (f106), phng trnh khng cho kt qu

tt. Phng trnh c th p dng cho ti liu log m thanh, tuy nhin trong gii hn gi tr

nht nh (

Trong :

- N: S thnh phn khong vt

- fi: t l th tch ca khong vt i, N

i

if 1

- Ki: modun khi ca khong vt i Phng php ca Voigt v Reuss cho ra kt qu khc nhau, nh gi Voigt cho kt qu cao hn

gi tr ca Reuss. Kt qu ca hai phng php nh gi ny to nn mt vng gii hn gi tr ca

modun khi Km. Trong , gii hn trn l ca Voigt (gii hn Voigt) v gii hn di l Reuss (gii

hn Reuss). Thng thng, gi tr modun n hi c ly trung bnh ca hai gii hn trn theo cng

thc ca Hill (KH).

2

RVH

KKK

Modun n hi ca mi loi khong vt bin thin trong mt gii gin cc gi tr. Bng 2.3.3

th hin cc gi tr modun n hi thng dng ca mt s khong vt. Khong vt st c ly gi

tr xp x, v n l loi khong vt gy ra cc gi tr khng chc chn trong phng trnh Biot-

Gassmann, bi gi tr modun n hi ca tng loi khong vt st thay i rt khc nhau (bng 2.3.4).

cho kt qu gii hn mudun n hi Km cht hn (gii hn trn v di gn nhau), ta s dng phng php nh gi ca Hashin Shtrikman (1963)

max

1

1max

_3

4

3

4

N

ii

i

UPHS

K

fK , min

1

1min

_3

4

3

4

N

ii

iLOHS

K

fK

Vi KHS_UP, KHS_LO ln lt l cc gii hn trn v di ca modun khi. max v min ng vi ng sut ct ln nht v nh nht ca khong vt thnh phn.

Tng t vi cch ly gi tr trung bnh ca Hill, ta c gi tr modun n hi hiu dng trung

bnh KHS.

2

__ LOHSUPHS

HS

KKK

Bng 2.3.3: Modun n hi v mt ca mt khong vt thng dng

(2.3.17)

(2.3.18)

(2.3.19)

Khong vt Modun khi K

(GPa)

Modun ct

(GPa)

Mt

(g/cc)

Quartz

Clay

Feldspar

Calcite

Dolomite

36.6

21.0

75.6

76.8

94.9

45.0

7.0

25.6

32.0

45.0

2.3.65

2.3.58

2.3.63

2.3.71

2.3.87

Bng 2.3.4: Modun n hi ca cc loi loi khong vt st (theo Avseth, 2005)

Khong vt st K (GPa) (GPa)

Smectite 1705 7.5

Illite 39.4 11.7

Kaolinite 1.5 1.4

Kaolinite 37.9 14.8

Kaolinite 12 6

Chlorite 95.3 11.4

Hnh 2.3.12 l mt v d tnh modun khi ca hn hp 2 khong vt: St Calcite theo cc cng

thc ca Voigt Reuss Hill v Hashin-Shtrikman. ng gi tr trung bnh tnh theo Hill v tnh

theo Hashin Shtrikman rt gn nhau. Gii hn Voigt v Reuss cho gi tr ln nht v nh nht trong

tt c cc phng php tnh.

Thuc tnh ca cht lu ph thuc ch yu vo mn ca nc, t trng du v kh, th tch

kh trong du (t s GOR) v p sut cng nh nhit . Mudun khi ca cht lu Kfl c tnh theo

cng thc trung bnh ca Reuss, vi gi thit cc pha ca cht lu phi phn b ng nht trong l

rng v quan h thy lc tt (gi thit (c) phng trnh Biot-Gassmann)

g

g

o

o

w

w

fl K

S

K

S

K

S

K

1

Trong : Kw, Ko, Kg ln lt l modun khi ca nc, du v kh.

Sw, So, Sg tng ng vi bo ha nc, du v kh.

Phng trnh (2.) cho thy nn ca hn hp cht lu bng tng nn ca tng cht lu

thnh phn. Vt liu cc mm v linh ng th cng d nn, do nn ca kh thng cao hn

nn ca du v nc mn (brine): Wog CCC . Cc gi in hnh modun khi ca cc cht lu l:

Kgas = 0.021 GPa, Koil = 0.79 GPa, Kw = 2.3.38 GPa.

Khi cht lu phn b khng ng nht (gi l patchy saturation), gi tr Kfl khng th nh gi

theo cng thc ca Reuss. Mc phn b ca cc pha cht lu c xc nh lin quan n thm,

nht v bng thng ca tn s (vi milimet i vi o log v vi mt i vi a chn). Ty thuc

vo kch thc ca vng phn b pha cht lu (patch size) m ta c cch nh gi Kfl khc nhau:

Khi kch thc vng phn b ln i vi bc sng a chn, s dng cng thc trung bnh

ca Voigt (domenico, 1976):

ggoowwfl SKSKSKK

i vi kch thc vng phn b trung bnh, gi tr modun khi cht lu c th tnh xp x bng phng trnh hm m (Brie, 1995):

Calcite

Clay

Hnh 2.3.12: Modun khi ca hn hp

khong vt st calcite c th hin theo

phn trm th tch khong vt st.

- ng mu en trn l gii hn

Voigt.

- ng mu en di l gii hn

Reuss

- ng mu l gii hn tnh theo

trung bnh ca Hill.

- Hai ng nt t trn v di v gii

hn trn v gii hn di tnh theo

HashinShtrikman

- ng nt t gia tnh theo trung

bnh s hc ca gii hn trn di

HashinShtrikman

(2.3.20)

(2.3.21)

(2.3.22)

ge

wgwfl KSKKK )(

th hnh 2.3.13 minh ha cho hai trng hp bo ha cht lu ng nht v khng ng nht. Kt

qu tnh VP theo bo ha nc khi thay th nc bng kh da vo phng trnh thay th cht lu

Biot-Gassmann. Khi cht lu phn b ng nht, modun khi ca cht lu gn bng modun khi ca

bo ha kh. Khi kh bt u thay th nc, vn tc gim mnh v vn tc sng truyn trong kh

nh hn nhiu so vi vn tc sng truyn trong nc. V khi kh dn thay th ton b nc th gi tr

VP tng nh tr li, iu ny l do mt khi gim dn khi nc c thay th bi kh (cng thc

(2.3.6)).

Gi thit quan trng nht trong l thuyt cht lu bo ha khng ng nht l vng phn b cht

lu khng c kt ni quan h thy lc vi cc vng xung quanh, do dao ng p sut trong 1 chu

k lan truyn sng s khng c cn bng tr li (p sut gia tng khng c tiu tn). iu ny c

ngha rng kch thc vng phn b cht lu khng nn nh hn chiu di phn tn cht lu L (m).

f

KkL

f.2

Trong :

- k: thm ca loi cht lu (m2)

Hnh 2.3.13: th quan h vn tc sng P v bo ha nc s dng phng trnh Biot-Gassmann. ng cong di th hin bo ha ng nht. ng cong trn th hin bo ha

khng ng nht vi v

. ng cong gia ng

vi bo ha khng ng nht:

v . Cc im

d liu c ly ca Lebedev (2009). 3 ng cong l thuyt ny c tnh trn kh.

(2.3.23)

- Kfl: modun khi cht lu (Pa)

- f: tn s sng (s-1)

- : nht ng lc hc ca cht lu (Pa.s)

- : rng

ng thi, tha mn gi thit cho phng trnh Biot-Gassman, th p sut l rng phi cn bng trong mi vng phn b cht lu. iu ny ng ngha rng kch thc vng phn b khng c ln hn chiu di phn tn cht lu. Do , vic ng dng thc t ca l thuyt ny ta chn kch thc vng phn b bng vi chiu di phn tn trung bnh cho tt c cc mu

M hnh thay th cht lu FRM (Fluid Replacement Modeling).

S dng phng trnh Biot-Gassman xy dng m hnh thay th cht lu nhm nh gi s bin i vn tc v mt khi bo ha cht lu thay i. M hnh FRM yu cu cc thng s cn thit:

a) B dy ca tng cha b) Vn tc sng P: S dng d liu log sonic c) rng hoc mt : Nhng vng c rng thp hoc th tch st cao cn c loi b, s

dng d liu gama log, mt hoc gi tr rng xc nh (cut-off). d) Vn tc sng S:

D liu VS cn c th tnh c Kdry. Thng tin v vn tc sng VS c th ly t cc ngun sau:

o vn tc sng ngang bng log sonic lng cc nh gi Vs bng cch s dng ng mudrock (phng trnh 2.3.10) Gi thit mt gi tr h s Poisson xc nh ca kh dry (th cc gi tr t 0.12 n 0.25

i vi ct kt) ng mudrock cho kt qu nh gi Vs thp hn thc t trong ct cha c kt, rng cao.

iu ny dn kt qu nh gi khng ng h s Poisson v Kdry. i vi nhng trng hp ny, thng thay th vic nh gi VS bng vic xy dng ng log tng hp (synthetic) VS vi gi thit VP/VS=2

e) bo ha cht lu: bo ha nc i vi iu kin ban u ca va c th c xc nh bng gi tr c th

hoc s dng ng log.

Cc thng tin bo ha phi ph hp vi gi tr mt v vn tc.

f) Thnh phn khong vt ca

g) Tnh cht ca cht lu: Xc nh ng trng hp bo ha ca cht lu (ng nht hay khng ng nht) nh gi

ng gi tr modun khi ca cht lu (cng thc 2. ).

Bc tnh ton quan trng trong m hnh FRM l tnh ton gi tr Kdry. Gi tr ny c th c tnh theo cc cch sau:

(1) i vi VP v VS bit, Kdry c th c tnh bng cch tnh gi tr Ksat u tin, sau s dng phng trnh Mavko (2.) nh gi Kdry.

(2) Nu khng c VS, Kdry c tnh bng cch: a) Gi thit ca gi tr h s Poisson kh. Dng phng trnh ton phng bc 2 (2.) tm

Kdry

b) S dng phng trnh ng mudrock nh gi trng hp bo ha nc, sau s dng phng php ca Mavko nh gi s thay i VP m khng c VS tnh ton cho trng hp cha Hydrocacbon (phng trnh 2.)

Hnh 2.3.14, 2.3.15, 2.3.16 m t kt qu tnh ton s thay i ca vn tc v h s Poisson theo bo ha nc, s dng phng trnh Biot-Gassmann cho hai trng hp ct bo ha kh v ct bo ha du. Ch trong cc m hnh ny, bo ha cht c gi thit l ng nht.

a)

b)

Hnh 2.3.14: th quan h gia vn tc (a), h s Poisson (b) v bo ha nc trong ct kt cha kh, s dng phng trnh Biot-Gassmann vi cc thng s:

M hnh c xy dng cho c 2 trng hp: ct bo ha nc, v ct bo ha 50% kh. Cc gi tr vn tc ca tng trng hp c th c xc nh trn th:

- Bo ha nc: VP=2500m/s;

VS=1250m/s;

- Bo ha 50% kh: VP=2000m/s;

VS=1305m/s;

b)

a) Hnh 2.3.15: th quan h gia vn tc (a), h s Poisson (b) v bo ha nc trong ct kt cha du, s dng phng trnh Biot-Gassmann vi cc thng s:

Ch rng, khng c s thay i nhiu v vn tc v h s Poisson. Tuy nhin, y l v d cho dead oil (du cht) khng c kh ha tan v hu ht cc va du u c t nhiu phn trm kh ha tan

2.4 Crossplot AVO Intercept A v Gradient B

2.4.1 Biu crossplot

Biu Crossplot th hin hnh nh mi lin h gia 2 gi tr v c s dng :

Trc quan cc gi tr ngoi lai m c th lm thay i mi tng quan ca cc bin,

t c mt gi tr trc quan tng quan mnh m gia cc bin,

Xc nh mi quan h gia cc bin l tuyn tnh hay khng tuyn tnh,

Xc nh cc xu hng ch ra cc tp hp lp trong cng mt b d liu,

Pht hin s lch quan trng t mt ng c s (background trend) ni cch khc l pht hin

cc d thng.

Xy dng biu crossplot c s dng rng ri hn trong k thut phn tch AVO bi v n

to ra s thun tin, ng thi, v lm cho bt c hai thuc tnh no tr nn c ngha. Ni chung,

cc n v thch hc v loi cht lu thng thng t gp cng nhau trong mt khong khng gian

biu AVO crossplot, cho php nhn din c hai ng c s thch hc (background trend) v bt

c tp hp di thng khng xu hng no (off-trend) c th lin quan ti hydrocarbon.

Ban u, k thut biu crossplot c bit s dng cho intercept v gradient. Goodway et al.

(1997) s dng crossplot ca cc thng s n hi. Cc thuc tnh khc cng c s dng nh

cc phng php nhn din d thng AVO (Castagna v Smith, 1994). K thut crossplot thch hp

cho mt cp thuc tnh do cc loi thch hc v cht lu thng thng tp hp cng nhau cho php

minh gii mt cch khng qu phc tp. Cc tp hp khng xu hng c th phi xc nh mt cch

phc tp hn l mt yu t gip nhn din hydrocarbon tim nng. Mt tnh cht phn tch v

minh gii biu AVO crossplot thnh cng, l tt c bin (tnh cht a cht dang quan tm) u

da trn d liu d thng c thng k trc.

Verm v hilterman (1995) gii thiu biu Crossplot to t d liu normal incidence (NI)

v h s phn x Poisson (PR) bng x dng biu thc tng ng Zoeppritz. Ri mu ha cc im

d thng trong biu c bn, sau th hin chng trn mt mt ct thch hc, ging nh i vi

mt mt ct a chn. Mt c trng ng quan tm trong bi tho lun ca h l tng xoay trc

ca biu NI-PR c th thay i d thng loi 2 thnh cc d thng AVO loi 3 gi, iu c

th c d dng vch ra.

Castagna v Swan (1997) xut thc hin crossplot AVO intercept vi gradient. H th

hin sinh ng s lin tc ca phn loi phn hi AVO c xut sm hn bi Rutheford v

Williams (1989), v h nghin cu thm mt dng im sng ct cha kh m bin ca chng gim

khi tng khong cch thu n (gi l AVO loi 4). S phn loi ca Castagna v Swan cho l ct cha

kh c nhiu loi khc nhau v bao gm hn hp phn x b lch khi ng c s.

Ngoi biu NI-PR v P-G (intercept-gradient), chng ta cn c th k n tn ca nhiu

loi crossplot khc c gi tr trong nhn bit thch hc v cht lu (nh Intercept- h s cht lu c

gii thiu trong Cambois (2000b), cc crossplot lin quan ti Vp, Vs hay Vp/Vs). Tuy nhin trong

phm vi n ny chng ti s gii thiu ch yu v biu crossplot th hin mi lin h hai thuc

tnh AVO Intercept Gradient. Bi bo Castagna et al. (1998) xut bn mt bn tng quan v minh

gii AVO intercepts v gradients. Mt trong nhng kt lun ca h t nhng phn tch tnh cht bin

- phn hi xc nh c nhng sau y:

Cc clastic bo ha nc, qua nhng di su gii hn v trong mt vng c bit, thng

th hin mt mi quan h r rng gia intercept v gradient, mi quan h ny c so vi ng

c s. Do , time-window cho sn, trong khi cc khng cha hydrocarbon s cho ta mt ng

c s, cc im d liu nm lch khi ng c s c th l biu hin ca hydrocarbon hoc cc

thch hc khc thng.

Gc ca ng c s (background trends) ph thuc th nht vo t s c s Vp/Vs. Khi t s

Vp/Vs tng, gc ca n tr nn dng hn ngha l, nu intercept chn dc theo theo trc x,

ng c s quay theo hng ngc chiu kim ng h.

Mt sai s quan trng t ng c s c kho st khi nc trong l rng ca c thay th

bi kh s dng phng trnh Gassmann. Vic thay th lm gim t s Vp/Vs. Do , t mt

mt phn x nc tng ct, bo ha kh cc b khin cho c intercept v gradient tr nn m hn

so vi khi chng l ct bo ha nc hon ton.

C ly su c chn cho crossplot intercept v gradient khng nn qu ln, bi v n c th

gy ra trong s chng cht ca nhiu ng c s lin quan n cc vng khc nhau. Hu qu s

dn ti ng c s khng r rng.

Chng ta thy vic xy dng biu crossplot thuc tnh AVO thng thng xc nh mt

ng c s cho phn x vi dc n khng cha hydrocarbon v th hin cc d thng AVO ng

ch nm ngoi ng c s . ng c s c hiu chnh t tnh cht . Do , lin h cc

d thng AVO vi tnh cht , cht lu th vic xc nh cc thuc tnh a chn vi xu hng tnh

cht l iu rt quan trng. Mt khi iu c thc hin, minh gii nh lng cc d thng c

th c hon thnh.

2.4.2 Xy dng biu crossplot AVO gia Intercept v Gradient

Vic thc hin xy dng mt biu crossplot cho hai thuc tnh bt k, u tin chng ta

lun cn tht phi bit gi tr ca n. i vi biu Intercept v Gradient, hai thuc tnh ny c

xc nh bi phng trnh Shuey (2.4.1).

R()=Rp+G Sin2 (2.4.1)

Vi:

Rp: Bin khi im thu trng im n (zero offset), hoc h s phn x gc ti chun (normal

incident reflectivity), hay thng gi l AVO Intercept

G l gc dc (slope) ca ng tuyn tnh, hoc h s gc ca phng trnh Shuey, hay thng

gi l AVO Gradient

R() l bin ng vi gc ti l

Cc bc c bn xy dng biu ny bao gm 3 bc chnh:

1. T d liu a chn bao gm ba gi chnh gn, trung bnh v xa (near, middle, and far angle

gather), c bin ti mt ct cn quan tm (Hnh 2.4.1a)

2. a vo biu vi trc tung l bin , trc honh l Sin2 vi l gc ti tng ng vi

bin c c v vit phng trnh tuyn tnh th hin mi quan h gia R() v Sin2 c

dng nh phng trnh Shuey n gin trn (Hnh 2.4.1b)

3. Thc hin ln lt vi cc mt khc nhau, v a Rp (Intercept - P) v G (gradient) vo biu

crossplot P-G ta c v tr tn hiu ti cc su khc nhau trong khng gian biu

crossplot.

Hnh 2.4.1: Phn tch AVO c bn sau hiu chnh hnh hc cc trace ring bit (mt ng

ring bit hnh a)) cho mt gi (gather) c th hin trong khung bn tri (a); mu xanh

dng th hin trace vi gc ti nh hn, mu th hin trace ti gc ti trung bnh v xanh

lc th hin gc ti xa. Mt biu s c v ti bt c cc mt no (vd: mt c su ng

vi thi gian t1, t2, hoc t3) phn tch s thay i bin theo khong cch thu n ti ;

biu bn phi cho ta thy ca mt t2. ng thng mu xm l ng tuyn tnh th hin

gn ng nht mi quan h gia hai thng s; gi tr P v G c ly ra t phng trnh ng

thng . Tam gic mu xm th hin bin trung bnh ca tt c cc trace t2. (Hnh 2 AVO

Analysis Demystified Roger Young v Robert Lopiccolo)

a)

b)

Sau khi chng ta c mt biu crossplot hon chnh cho b d liu, vic tip theo l

minh gii chng. lm c iu chng ti s gii thch r hn v crossplot P-G. Nh chng

minh bi Smith v Gidlow (1987) v nhng tc gi khc, trong trng hp Intercept v Gradient, ti

vng khng c mt hydrocarbon thng s hnh thnh c mt background trend r rng khi xy

dng biu . S lch khi background trend c th l du hiu ca hydrocarbon.

Vic minh gii cho biu ny c th tr nn phc tp do (1) s thiu trc gic cm nhn

trn t cch ngi minh gii i vi ngha quan trng ca yu t Gradient, (2) cc hiu ng trng

lp ca gn sng (wavelet), (3) s ri rc bi cht lng d liu a chn, v (4) Khng c nh hng

ca d liu a vt l trong chit tch thng s intercept v gradient.

hnh 2.4.3 m t v tr ca cc loi tn hiu AVO th hin trn biu crossplot intercept

(trong biu ny k hiu l R0) v Gradient (G). Nh gii thiu phn trc, biu ny c

chia lm bn gc phn t (I-IV) v c mt ng c s (background trend) th hin v tr ca ct cha

nc v cc chm en th hin v tr cc d thng AVO v chng c th ln quan n hydrocarbon.

Hnh 2.4.2: Bn tri, biu th hin mi quan h P v G cc mu khc nhau ti cc su

khc nhau (thi gian khc nhau) trong mt b d liu a chn. D liu c chun ha rng

buc P v G ti cng mt di gi tr. Bn phi, cng biu ny c t mu ln cho thy bin

cng ti tng im; mu xanh nht cho ti m th hin bin m vi gi tr t nh ti

ln (trough); mu nht cho ti m th hin bin dng c gi tr t nh ti ln (peak). Ba

vng 1, 2 v 3 c phn chia theo ba loi AVO ca Rutherford v Williams. (Hnh 3 AVO

Analysis Demystified Roger Young v Robert Lopiccolo)

Tnh tng t ca ng phng cht lu c xu hng trong biu crossplot ca s thi

gian (time-window) c to thnh mt cch r rng t a chn, v nhiu ngi cho rng chng nh

nhau. Thc t, c cc m hnh v d liu thc u cho thy khi to ra, chng khng cng mt kiu.

Cc ng phng ca crossplot thc ph thuc mt cch c bn theo cch m crossplot c xy

dng (tc theo cc tng trong biu crossplot ca s thi gian), phn ln nhiu lin quan ti tn hiu,

v ln ca bt c hiu ng no lin quan ti hydrocarbon (vd: hiu ng kh). Trong khi cc thng

tin tnh cht vn nm trong AVO crossplot, vn khng d thy nhng ng phng (ng c s

- trend line) r rt, bi v cc nh hng ca nhiu.

2.4.3 Mt s yu t nh hng trong crossplot

Tn hiu v nhiu. Xem xt mt im ring bit trong gc phn t bn phi pha di trong

crossplot (hnh 2.4.4a). im ny c to t thuc tnh AVO (t hi quy bnh phng cc tiu) vi

phn x pha 0 n ln nht trong mt gi tng hp (synthetic gather) loi nhiu. N cho thy

mt dng phn hi loi 1 t nc tng ct c kt cha nc b ph ln bi lp st bn trn (bin

gim khi tng khong cch thu n). S biu din ny c th c gi l horizon crossplots v lin

quan ti mt b mt phn x ring bit.

Nu d liu t mt s gi c phn x nh nhau c biu din, th tn hiu crossplot s

ging nhau mt im duy nht trn crossplot. Tuy nhin nu tn hiu nhiu c a vo

Lm r mi quan h gia cc

phn hi AVO nc tng ct v

biu crossplot

H thng ch s cc gc phn

t theo Castagna et at (1998)

ng phng tnh cht ca theo l

thuyt vi cha y nc (Vp/Vs=2 vi

cc lp trn v di) Background trend

Hnh 2.4.3. Cc loi AVO v biu crossplot. (Hnh 1 The anatomy of AVO crossplots Rob

Simm, Roy Write v Richard Uden)

Hnh 2.4.4: Phn tch biu AVO crossplot. (a) Phn x loi 1, (b) Sng nhiu trong o

lng gradient trn nhiu gather, (c) nh hng ca rng, (d) nh hng ca kh, (e)

tch ra ty , (f) crossplot ca s thi gian (time-window). (Hnh 2 The anatomy of AVO

crossplots Rob Simm, Roy Write v Richard Uden)

a) b)

c)

e)

d)

f)

trn gi (nh l s gim t l tn hiu/nhiu (S/N) khi khong cch thu n tng), phn hi trn crossplot

tr thnh mt tp oval phn b xung quanh im ban u (hnh 2.4.4b). l bi nhy khi c

lng gradient m c nhiu. Hendrickson gii hn chng thnh elip nhiu. Tn hiu nhiu ny c

xu hng d dng nhn thy trong d liu thc, v d nh biu ha mt lng mu nht nh t

cng mt tng t mt mt ct a chn. S m rng ca xu hng (hnh elip) song song vi trc

gradient l du hiu ca lng d liu nhiu. Trong d liu thc, phng ca nhiu thng c gc

dc (slope hoc gradient) khong -5 hoc ln hn. Cc nh hng ca cc loi nhiu khc (nh

RNMO) s khng c bn y.

Cambois nhn thy gc dc ca ng phng nhiu ph thuc vo thi gian di chuyn

ca sng (two way time traveltime), cu trc vn tc v khong cch thu n. Trong d liu thc v tr

chung ca b d liu (ging nh hnh 2.4.4b) ph thuc vo t l tng i ca R0 v G (c th b nh

hng bi hiu chnh ng hoc bin v (break) khng c hiu chnh). Tuy nhin, gc dc ca

ng xu th nhiu khng ph thuc t l ny.

Mc d tn hiu nhiu ngu nhin xut hin tr thnh thnh phn c s ca nhiu trong AVO

crossplot, cc loi nhiu khc cng c th nh hng n ng c s (v d nh RNMO).

rng v thnh phn st. Mt s thay i trong thch hc c th c m hnh ha bi s

thay i rng trong ct hoc do thnh phn st. S tng rng c hai h qu - gim AVO gradient

(t s Poisson tng phn vi lp st pha trn gim). S gim intercept khin cho ng phng

rng c gc nh ct qua trc gradient.

S thay i ca ct trong m hnh (nhng vn duy tr tiu chun phn x khng giao thoa)

gy nn trong crossplot mt chui cc hnh elip thng hng mt gc vi trc gradient (hnh 2.4.4c).

Cc ng phng c p t bng mt trong cm d liu c th ch no gia ca ng

phng nhiu v ng phng rng.

S thay i thch hc bi v s tng thnh phn st ca ct cng c gradient v intercept thp

hn, nhng dc hn ng phng rng. N c th st hn vi ng phng nhiu. Trong trng

hp m thnh phn st trong lp ct khc so vi lp st bn trn (nh c th thy bin gii nhp

(sequence boundary)), v xu th thch hc s c gi tr intercept khc khng.

Nhng iu nu trn chng minh rng khu vc c cho c th c mt ng c s nhng a

dng (da trn s phn b tng i ca st v rng m ln lt c xc nh t cc tng trm

tch). l mt quan im ng bn, tuy nhin, trong thc nghim tn hiu nhiu s lm ng phng

thch hc khng r rng.

Hiu ng kh. Hnh 2.4.4d cho thy nh hng ca cht lu trong ct vi cc rng khc

nhau. nh hng ca hydrocarbon l khng nhiu to nn mt xu th tch cm d liu v v tr

bn tri ca cc im d liu ct cha nc. nh hng ca hydrocarbon ln t l Vp/Vs ca ct cng

ln, cc im d liu cng cch xa khi im d liu c s.

Trong nhng m hnh ny, s phn tch ti u c th c xc nh bng thng k (hnh 2.4.4e). N

s ph thuc vo ln ca nhiu, s thay i thch hc, v ln ca hiu ng kh. ng phng

ny c th hoc khng i qua gc ta . Trong trng hp thc t, kin thc v ng phng nhiu

c th c s dng m hnh ha phn chia ti u (cho rng b qua cc nh hng khc ti G v

R0). Nu s thay i thch hc khng ln, mt di hng c th tn ti m c th chia ra tt nh nhau.

2.4.4 Mi quan h gia intercept (A) v gradient (B) ng c s.

Thay v s dng k hiu P (R0) v G, phn ny chng ti s s dng k hiu A v B biu

din gi tr intercept v gradient khi a vo tnh ton ng c s.

Cc thng s Vp, Vs v thng tng quan cao vi cc thng s lch ti hydrocarbon

hoc thch hc phi truyn thng. Mi tng quan ny p dng vo mi quan h gia h s phn x

gc A v B

Phng trnh Gardner:

Castagna et al (1998) cho rng background bao gm ct kt v st bo ha nc, u tin, mt

khng i theo thi gian, vn tc tng thm mt gi tr bng g ln ban u (ty ). Gardner et al.

(1974) cho thy g bng cho hu ht cc loi trm tch. Vi s thay i nh trong vn tc ta c:

()~

Vp

()

Mi quan h c th b anh hng mnh bi ranh gii thch hc. ngha ca sai s s c bn

sau.

Mi quan h Vs vi Vp

Vi mt nhp bo ha hon ton nc ca cng mt tui v thnh phn, chng ta c th cho rng

c mi quan h tuyn tnh gia Vp v Vs khng b nh hng bi s khc bit thch hc. V d,

Castagna et al. (1985) cho thy st v ct kt bo ha nc thng i theo mt xu hng, ging

nh l ng mudrock. (Bi v s thay i xu hng ny ph thuc vo a cht khu vc, chng ta

khng th c mt bin s ton cu; tuy nhin, sai s thng l 5%. Sai s nh vy c th nh hng

ln ti phn tch AVO). Thay v hn ch vi h s mudrock line c th, chng ta s lm n n gin

li, vi mt su ca s nht nh ti mt khu vc cho trc, c mt vi mi quan h tuyn tinh

gia Vp v Vs:

Vp = mVs + c

Vi m v c l h s thc nghim.

Phng trnh chung intercept vi gradient

Phng trnh Aki v Richards (1980):

R() A + B sin2() + C sin2()tan2()

Vi:

(2.4.2)

(2.4.3)

(2.4.4)

=1

2 (

Vp

()+

())

=1

2

Vp

() 2 (

Vs

())

2

(2Vs

()+

())

=1

2

Vp

()

Khi Vp l s thay i sng nn P dc theo b mt (Vp2 Vp1), Vp l vn tc sng P trung bnh

[(Vp1+Vp2)/2], l s thay i dc theo b mt (2 1), () l mt trung bnh [(2 + 1)/2], tng

t i vi Vs v Vs cho sng ct S. Vi Vp1, Vs1, 1 v Vp2, Vs2, 2 l cc tnh cht trung bnh ca

mi trng th nht (nm trn) v th hai (nm di). Ch l A l dng tuyn tnh ca h s phn

x sng P (Rp).

T phng trnh (2.4.3) v (2.4.6), ta c phng trnh cho mt phn x background mt A-B:

=

1 + [1 4

(Vs)

()(

2

+

()

()) ]

Mi quan h chung ny cho php o ln ty bin ca phng trnh Gardner v ng cong Vp vi

Vs. By gi chng ta s xem xt bn trng hp cho ng c s.

ng c s (background trend): Vp/Vs v mt khng i

Nu Vp/Vs l hng s, c phi bng khng, v

m = Vp/Vs = (Vp)/(Vs) = Vp/Vs

Cho = 0 (mt khng i) trong phng trnh (2.4.5) trong khi bin g = 0 v thay phng trnh

(2.4.9) vo phng trnh (2.4.8) ta c:

A = Vp/(Vp)

V

= [1 8 ((Vs)

())

2

] .

Phng trnh (2.4.11) tng ng vi phng trnh (14) trong Foster et al. (1997).

ng c s (background trend): Vp/Vs khng i v mt Gardner.

Thay v cho rng mt khng i, by gi ta s dng quan h Gardner (2.4.2).

Vi g= 1/4 v m = (Vp)/(Vs) (Vp/Vs khng i)

A = 5/8 Vp/(Vp)

(2.4.5)

(2.4.6)

(2.4.7)

(2.4.8)

(2.4.9)

(2.4.10)

(2.4.11)

(2.4.12)

V

=4

5[1 9 (

(Vs)

())

2

] .

Phng trnh (2.4.13) cho thy ng ca hng s (Vp)/(Vs) i qua gc ta . Thm na, gc dc

ca ng c s ch ph thuc vo t s (Vp)/(Vs). Hnh 2.4.5 cho thy khi (Vp)/(Vs) tng, gc ca

ng c s tr nn dng hn (ng phng quay ngc chiu kim ng h vi A dc theo trc

x).

Rt hu ch khi ch rng vi phng trnh tng ng Wiggins {(Vp)/(Vs)=2.0}, t phng trnh

(2.4.5) v (2.4.6) ta c B = A bt k mi quan h ca mt v vn tc. Do , s ri rc lin quan

mnh m ti phng trnh Gardner s nh khi (Vp)/(Vs)=2.0.

V

~1

2 (

Vp

()

())

Vi Rs l h s sng S, r rng Rp Rs lun lun bng khng khi (Vp)/(Vs) khng i. Hn na, vi

trng hp c th khi (Vp)/(Vs)=2.0, ta c

~ +

2= 0

Cng cn ch rng trong phng trnh (2.4.13) th B = 0 khi (Vp)/(Vs) = 3.

ng c s (background trend): Vp v Vs c quan h tuyn tnh

Mc d (Vp)/(Vs) khng i c th ng l hu dng cho nhng di su gii hn, mi quan h

tuyn tnh gia Vp v Vs vn c v ph bin hn. T phng trnh (2.4.3), ta c:

(Vp) = m(Vs) + c

= =

()

()(

()

())

()=

()(

()

() )

v

~ 1

2

()(

() )

(2.4.13)

(2.4.14)

(2.4.15)

(2.4.16)

(2.4.17)

(2.4.18)

(2.4.19)

T phng trnh (2.4.19), ta c th thy Rp Rs nh t l vn tc tng phn bi s thay i

chm chp trong thnh phn background. Rp Rs s c phng i khi vn tc background gn vi

c bn trn v gim bt khi vn tc background cao. Tng t, h s phn x Poisson gi nh, c

nh ngha bi Smith v Gidlow (1987) v ph bin bi Verm v Hilterman (1995) gia nhng th

khc c cho bi:

() ~2( )

Vi l s thay i h s Poisson theo mt v () l h s Poisson trung bnh

Bin g = v ()

()=

1

(1

())

Thay vo phng trnh (2.4.7) ta c

Hnh 2.4.5: Biu h s phn x zero-offset (A) vi AVO gradient (B) cho khi Vp/Vs khng

i v mi quan h Gardner. ng c s xoay ngc chiu kim ng h khi Vp/Vs tng. (Hnh

1 Framework for AVO gradient and intercept interpretation, 1998, John P.Castagna, Herbert

W.Swan, v Douglas J, Foster)

(2.4.20)

(2.4.21)

=4

5[1

1

(())2 (() )(9() )]

Vi A c cho bi phng trnh (2.4.12)

Theo phng trnh (2.4.22):

1) ng c s i qua gc ta (A = B = 0)

2) Nh hnh 2.4.6, khi (Vp) gim [v (Vp)/(Vs) tng theo phng trnh (2.4.16)], gc dc ng c

s tr nn dng hn (quay cng chiu kim ng h). Hnh ny cho ta thy gc ng xu hng

mudrock m l 1.16 v h s c l 1.36 km/s c cho trong Castagna et al. (1985). Ch rng gc

dc ng c s thay i t ngt vi vn tc thp hn 2.5 km/s. Kh c th k vng c mt

ng c s r rng vn tc thp hn.

3) Kt lun ny tng t vi trng hp (Vp)/(Vs) khng i. Tuy nhin, vi (Vp)/(Vs) cho trc,

cc gc dc khng cn thit phi bng nhau hai trng hp. Nh rng, vi mi quan h tuyn

tnh Vp v Vs, Vp/Vs thay i dc theo b mt thay v khng i. Kt qu l mt ng c s

khc ti (Vp)/(Vs) cho trc.

4) Phng trnh (2.4.22) tr thnh phng trnh (2.4.13) khi c = 0

Cho mt khng i (g = 0), thay v mi quan h Gardner, cho

= [8

()

()] = [1 8 (

()

())

2()

() ] .

Phng trnh ny tng ng vi phng trnh (15) trong Foster et al. (1997).

So snh cc ng c s

Trong hnh 7 cho thy gc dc tnh ton ca ng c s (B/A) l hm theo (Vp)/(Vs) vi:

1) Mt khng i v Vp/Vs khng i theo phng trnh (2.4.11)

Hnh 6: Biu lin h A-B c

cho khi Vp v Vs tuyn tnh

(m=1.16, c=1.36 km/s) v quan h

Gardner. ng c s xoay

ngc chiu kim ng h khi Vp

gim. (Hnh 2 Framework for

AVO gradient and intercept

interpretation, 1998, John

P.Castagna, Herbert W.Swan, v

Douglas J, Foster)

(2.4.22)

(2.4.23)

2) Mt Gardner v Vp/Vs khng i theo phng trnh (2.4.13)

3) Mt khng i v Vp tuyn tnh Vs c tnh ton bng ng mudrock (m=1.16 v

c=1.36 km/s), s dng phng trnh (2.4.8)

4) Mt Gardner (g=1/4) v Vp tuyn tnh (mudrock) Vs t phng trnh (2.4.8).

Vi n (bin) tng phn thch hc nh trong phng trnh tng ng Aki v Richards

(1980), mt mi quan h tuyn tnh tn ti gia A v B. [Foster et al. (1997) cho thy lm sao mi

quan h tuyn tnh b nh hng vi tng phn n hi ln, nhng ch nu (Vp)/(Vs)2]. B/A

tng khi (Vp)/(Vs) tng trong mi trng hp. Ch quan trng rng mt tng i t quan trng

hn so vi tng quan Vp vi Vs. Gi tr Vp/Vs khng i hay Vp tuyn tnh vi Vs to nn ng

c s khc hn nhau. Vi trng hp Vp/Vs khng i, B/A tr nn dng ti Vp/Vs bng hoc ln

hn 3. Do , mt gi tr A m ln c th gy nn B m ln dn ti ln bin tng khi khong

cch thu n tng vi khng tim nng. N c th xy ra trong ct hoc st cha c kt ni m Vp

v Vs khng tng quan mnh nh cc c kt tt. Xem s so snh d liu Hamilton (1979) vi

ng mudrock trong Castagna et al. (1985). Vi quan h tuyn tnh Vp v Vs, B/A tr nn dng

ch ti ni (Vp)/(Vs) rt cao cho gn ti 10.

Hnh 2.4.7: Biu B/A vi

(Vp)/(Vs) vi cc ng c s

gi thuyt khc nhau: Mt

khng i, Vp/Vs khng i;

Vp/Vs khng i, mt

Gardner; Vp/Vs tuyn tnh,

mt khng i; v Vp/Vs

tuyn tnh, mt Gardner.

Trong tt c trng hp, B/A

tng khi Vp/Vs tng. (Hnh 3

Framework for AVO gradient

and intercept interpretation,

1998, John P.Castagna,

Herbert W.Swan, v Douglas

J, Foster)

2.5 ng dng AVO

Pht hin kh

Phn ln, pht hin kh l mt trong nhng ng dng y trin vng ca phn tch AVO. T s

Vp/Vs thp c trng ca ct cha kh c hy vng cho php thy s khc bit vi cc lp c kahngs

m thp khc, nh l than hay ct cha nc (Castagna et al., 1993). Rutherford v Williams (1989)

nh ngha ba loi d thng ct cha kh AVO. Loi 1 ca h xy ra khi h s gc phn x sng P

dng mnh v cho thy s gim bin mnh theo khong cch thu n v pha thay i ti khong

cch thu n ln (Hnh 2.5.61).

Loi 2, vi h s phn x sng P nh, cho thy mt s thay i phn ln trong AVO. Trong

trng hp ny, nu h s phn x gc ti dng nh, mt s i pha ti khong cch thu n gn hoc

trung bnh s xy ra. Cc d thng loi 3 (Rutherford v Williams, 1989) c mt h s phn x gc

ln, n s tr nn m hn khi khong cch thu n tng (y l im sng c in). Mt phng php

thc hin thng c p dng vi st qua mt phn x ct cha kh l h s phn x tr nn m hn

khi khong cch thu n tng (Castagna v Backus, 1993).

Nhng trong c s xy dng biu AVO crossplot, Castagna v Swan (1997) gi ct cha

kh c ph ln bi st nn c phn chia da trn v tr ca mt A-B, thay v ch bng h s phn

x gc. Ct loi I (Castagna et al., 1997) c khng m cao hn lp bn trn. Chng xy ra trong

gc phn t th IV ca mt A-B. H s phn x gc gim khi khong cch thu n tng. Ct loi 2

(Castagna et al., 1997) c khng tng t nh lp bn trn. Chng cho thy s thay i ln trong

Hnh 2.5.1: H s phn x sng P vi b mt

st/ct cha kh vi mt di gi tr R0. H s

poisson v mt ca st c cho rng c

gi tr 0.38 v 2.4 g/cm3. H s Poisson v

mt ca ct cha kh c cho rng c

gi tr l 0.15 v 2.0 g/cm3 (Rutherford v

Williams, 1989). (Hnh 1 A review of AVO

analysis Hongbo Zhang v R. James

Brown)

biu hin ca AVO v c th nm gc phn t II, III, v IV ca mt A-B. Ct loi 3 (Castagna v

Swan, 1997) y c khng cao hn vi lp bn trn v thng sng. (Hnh 2.5.2).

Cu chuyn ni ting nht trong pht hin kh trong tng cha ct s dng phn tch AVO l

n ca Fatti et al. (1994). H thc hin mt k thut gi l Geostack (Smith v Gidlow, 1987). H s

cht lu (Smith v Gidlow, 1987) y c nh ngha l:

= 1.16

Vi Rpp = H s gc phn x sng P, W = vn tc sng S trung bnh, V = vn tc sng P trung

bnh, Rss = h s phn x sng S.

S thnh cng ca du vt F trong pht hin ca kh ph thuc phn ln vo s phn tch

trong crosspot W vi S vi ct kt cha kh, trn mt kha cnh, v ct kt cha nc v st trn kha

cnh khc. (Hnh 2.5.3)

pht trin phn tch Crossplot, Ross v Sparlin (2000) s dng k thut hin th. H

thy rng bic minh gii d liu crossplot vi k thut hin th 3D cho php nhanh chng pht hin

ng c s (background trend) v cc d thng vi mt lng ln d liu (Hnh 2.5.4)

Vi s ni ln ca cc phng php o sng, Garotta v Granger (1987) thc hin nghin

cu v tn hiu nhn trong sng o v sng nn v x l trong mi trng ct/st trn lp carbonat

s dng mt nh du phn x tt. H so snh phn hi trong ch sng P v ca ch P-SV vi

s lin quan ti cc im sau: bin thay i theo gc ti trong ct cha kh; bin suy gim qua

lp ct cha kh ; vi sc ph lin tc. Cc phn hi l thuyt t m hnh su thc hin theo phng

trnh Zoeppritz c so snh vi d liu thc, cho thy s ph hp hp l (Hnh 2.5.5 ti 2.5.9).

Hnh 2.5.2: Cch phn loi mi hn

chnh t ca Rutherford v Williams

(1989) vi ct loi 1 ( khng cao) v

loi 2 ( khng thp). Tuy nhin, khc

vi loi 3 c chia nh lm hai loi l

loi 3 v 4. Ct loi 4 th quan trng

hn trong th hin biu hin tng

phn AVO thc hnh v xy ra

trong nhiu bn trn th gii, bao gm

Vnh Mexico (Castagna v Swan,

1997). (Hnh 6 A review of AVO

analysis Hongbo Zhang v R. James

Brown)

(2.5.1)

Vic dng phn tch AVO trong pht hin kh l s dng l thuyt ba pha kiu Bios bi Carcione

v Tinivella (2000). Mt phn x y (BSRs) trong a chn c gii thch cho thy tn hiu a chn

trong nn thnh h Gas-hydrate. Mt vng kh t do c th hnh thnh ngay di BSR (Carcione v

Tinivella, 2000). Nghin cu ca h cho rng BSR c gy nn bi mt b mt phn ct Gas-hydrate

v trm tch cha kh t do. H kt lun rng ni tp trung cao ca Hydrate c th c pht hin khi

Hnh 2.5.3: Biu crossplot ca

vn tc sng P v vn tc sng S

(Fatti et al., 1994; theo Castagna et

al., 1985). (Hnh 9 A review of AVO

analysis Hongbo Zhang v R.

James Brown)

Hnh 2.5.4: m my en

trung tm c gii thch l

cho cc gi tr intercept ng,

A (trc ngang) v Gradient, B

(trc ng).

h cho cc d thng dng, m tng ng, v phn x sng P ti S l ch s pht hin tt trong

phn ln kh t do v kh hydrate (Hnh 2.5.10, 2.5.11)

Hnh 2.5.5: M hnh su -

Depth model (Garrotta v

Granger, 1987)

Hnh 2.5.6: D liu tng hp -

Synthetic data (Hnh 2.5.5) bng

phng trnh Zoeppritz (Garotta

v Granger, 1987)

Hnh 2.5.7: D liu thc cho thy

ch yu mt H4 (Hnh 5 v hnh 6)

(Garotta v Granger, 1987)

Trong vng thm d a chn, mt th thch c th phi i mt bi nh a vt l l xc nh

kh nng p dng v hiu qu ca AVO trong khu vc . Ci m thng thiu trong qu trnh quyt

Hnh 2.5.8: wavelet P v P-SV trong

mt H4 thay i theo gc ti; sng

P-SV c nh hng AVO r rng

(Garotta v Granger, 1987).

Hnh 9: Ph tn s sng P v P-SV;

sng P-SV ni rng ph (Garotta v

Granger, 1987).

Hnh 2.5.10: H s phn x P-P thay i theo

gc ti (Carcione v Tinivella, 2000

Hnh 2.5.11: H s phn x P-S thay i theo

gc ti (Carcione v Tinivella, 2000

Hnh 2.5.9: Ph tn s sng P v P-

SV; sng P-SV ni rng ph

(Garotta v Granger, 1987).

nh l li cht lng o lng gy ra bi s truyn v o sng. Swan (1991) tho lun trong nm

trng hp ngun nhiu thng thng trong c lng AVO intercept/gradient, bao gm co dn NMO

v s hiu chnh lp mng. Dong (1999) t cc vn lin quan ti kh nng pht hin AVO khi c

s xut hin ca s co dn v iu chnh lp mng gi trong nn tng nghin cu ca Swan (1991) v

ca chnh ng y (Dong, 1996). Hai tiu chun n gin t c ti xc nh s thay i nh trong

Vp/Vs vn thit cho mt s kin AVO tn ti s nhim gy ra bi hiu ng ca co dn ng v iu

chnh lp mng. Trong trng hp co dn n thun, iu kin c th nhn bit c cho bi Dong

(1999) l:

||

> 0.15 2||

Vi |A|max l gi tr intercept ln nht vi nn phn x m gn vi mt phn x AVO, =Vp/Vs.

Trong trng hp a iu chnh thm vo co dn, yu cu ca iu kin pht hin nghim

ngt hn nhiu v bao gm c thng s lp mng. iu kin pht hin trong trng hp ny (Dong,

1999) l:

||

> 0.41 2||

Vi l thng s lp mng v = 2h /0, 0 = Vabove /f0.

D on thch hc

Tn hiu a vt l x l AVO thch hc ph thuc vo Vp/Vs. Castagna et al. (1985)

bao gm vn tc sng ct gn nh c quan h tuyn tnh vi vn tc sng nn cho c trm tch

siliclastic bo ha nc v kh (Hnh 2.5.12).

Ri Hilterman (1990) tng hp li hai bc trong phn tch AVO: (1) tch cc tnh cht

t gi CDP (CDP gather), v (2) tng quan thch hc ti cc tnh cht c tch. Ch ti bc

Hnh 2.5.12: D liu sng siu

m phng th nghim vi cc

loi ct kt khc nhau di c

iu kin kh v bo ha. D

liu kh (k hiu vng) v bo

ha (k hiu c) c biu

ha vi cng iu kin p

sut hiu dng v lin kt bi

ng buc (Castagna et al.,

1985)

(2.5.2)

(2.5.3)

u tin, Shuey (1985) gii thiu mt biu thc cho phn hi a chn AVO trong cc trng hp

ca cc tnh cht . Mt phng trnh tng ng h s gc Shuey l:

R() R0 cos2() + 2.25 sin2()

Vi R0 l h s phn x gc ti v l s thay i h s Poisson t trung bnh ln ti thp hn.

Verm v Hilterman (1995) thy rng nu t s vn tc sng S vi vn tc sng P l khong

0.5 v cc trng hp ri vo di 300 khng c ngha, th phng trnh Shuey (1985) c th gim

xung hai bin, mt bin phn x gc ti, NI, v bin phn x gc ti ln, PR. Do :

R() NI cos2() + PR sin2()

Vi NI v PR c nh ngha bng:

=22 1122 + 11

= 0, =2 1

(1 )2

Vi cch ny, mt thng s x l n (NI) c m rng thnh hai thng s x l (NI v PR).

Bng cch m ha mu biu NI PR, vic phn chia tr nn hiu qu hn pht trin thch hc

bi v s phn tch cm phn x tng ln (Hnh 2.5.13)

Sau , Goodway et al. (1997) gii thiu, (1) s phn chia a vt l c pht trin cho tnh

cht s dng v nhiu hn phn tch Vp/Vs truyn thng; (2) s xuyn sut tnh vt l ln

hn bi tnh cht va cha c lp vi cht lu v thch hc vo thng s modul hoc thng s

Lam trong cc phn hi a chn ca chng; (3) d dng to ngng biu crossplot AVO hn cho

loi stack nhy hn h s cht lu , , (4) mt stack mi cho thy vng kh m khng cn

gii thch ngng hoc la chn h s cht lu.

Foster v Keys (1999) u t xa hn vo cc nh hng ca s thay i tnh cht trong phn

hi AVO. Nhn mnh chnh xc ca h cho intercept v slope (gradient):

B = (1 82)A 4 (1 )+ (1 2 )O(A2 )

Hnh 2.5.13: M ha mu

(thang xm) mt bng khung

chuyn t hai trace n bn tri

thnh mt trace n bn phi

(Verm v Hilterman, 1995)

(2.5.3)

(2.5.4)

(2.5.5)

(2.5.6)

Cho thy rng ng phng cht lu c ri rc t nht khi Vp/Vs = 2, v y phn x tng

ct ni bt hn so vi nc tng ct (Hnh 2.5.14)

ng c s quan trng bi s phn hi t ct t hoc st, ni c tng phn Vp/Vs thp,

c xu hng nm trn ng c s; cc phn x t ct cha kh th khng. Gray et al. (1999) a ra

hai phng trnh AVO mi lin quan ti s thay i ca bin a chn theo khong cch thu n

vi c s modul n hi v modul ct, , mt , v cc modul khi khc hoc modul Lam th

nht, . Cc tnh phn x ca tnh cht c s c t cc phng trnh hiu chnh ging vi gi tr ly

trc tip t well logs.

Kelly v Ford (2000a) lp ra s minh gii biu thuc tnh AVO crossplot c th n gin

ha bng dng s tht rng s thay th c kho st t ng c s l kt qu ca cng cc s thay

th vi cc tnh cht tng phn ca ring l. S thay th cung cp cho ta thng tin khng ch v

tnh cht thay i dc theo b mt m cn v lm sao chng thay i trong khng gian v thi gian

(Kelly v Forrd, 2000b) (Hnh 2.5.15 v 2.5.16)

Bt ng hng (Anisotropy)

Nhn mnh cho h s phn x P-P ti b mt c t nht mt mi trng l bt ng hng th

rt phc tp; tuy nhin, cc nghin cu thc nghim v phn tch cho thy s bt ng hng c

th c nh hng quan trng n phn tch AVO (Wright, 1987; Banik, 1987; Mallick v Frazer,

1991; Kim et al., 1993; Blangy, 1994). Ruger (1997, 1998) a ra gii php phn tch phn tch

tng ng m cho ta trc quan v xuyn sut trong nh hng ca tnh ng hng ngang, c VTI

v HTI, trong tn hiu AVO. Ruger cho thy s thay i theo khong cch thu n ca h s phn x

sng P nhy nh vi bt ng hng nh, v trong trng hp HTI cng nhy nh vi gc phng v.

ng cng chng minh rng phng trnh tng ng ca ng tng t Aki v Richards (1980)

cho kt qu sai s cho gc ti ln hn.

Hnh 2.5.14: ng c s d on

t phng trnh (2.5.6) theo gi tr

gradient (B) v intercept (A).

(Foster v Keys, 1999)

Hnh 2.5.15. Biu s thay th

P-S lin h vi mt v Vs trong

trng hp biu D0 D1 (Kelly

v Ford)

Hnh 2.5.16: S thay th st/ct

cha nc v s thay th thm

vo bi v s thay i ca

hydrocarbon. Tng hp cc s

thay th ny gy nn s thay th

st/ct cha kh. (Kelly v Ford,

2000b)

CHNG 3: S DNG PHN MM HAMPSON RUSSELL SUITE

(HRS) TRONG VIC PHN TCH V MINH GII AVO

3.1 Gii thiu v CGG v phn mm Hampson Russell Suite

CGG (Compagnie Gnrale de Gophysique) l mt cng ty dch v a vt l ca Php c

thnh lp vo nm 1931.

Cng ty cung cp cc dch v v thu thp d liu, x l v minh gii a chn, cng nh cc

phn mm x l v minh gii lin quan n khch hng trong thm d v khai thc du kh vi qui m

thng mi. Vo thng 1 nm 2007 CGG st nhp vi i th cnh tranh l cng ty Veritas v c

i tn thnh CGG-Veritas. n thng 1 nm 2013, cng ty li i tn thnh CGG sau khi mua li

Geosciene Division ca Fugro. T CGG tr thnh tn chnh thc ca cng ty cho n thi im

hin nay.

Khch hng ch yu ca CGG l cc cng ty du kh s dng hnh nh a chn trong thm d,

pht trin v khai thc cc m du v kh t. Hnh nh a chn c s dng xc nh cc khu

vc mi, ni cc iu kin di b mt thun li cho s tch t du kh, xc nh kch thc v cu

trc ca cc m du kh, ti u ha s pht trin v khai thc cc m du kh. Ngoi ra, CGG cng

ch to cc thit b a vt l

3.1.1 Gii thiu v CGG

3.1.1.1 Lch s

a) CGG

Trong nm 1926, hai anh em nh Schlumberger: Conrad Marcel, hnh thnh Socit de Thm

d Electrique (SPE) chuyn v khai thc du m v than cng nh cng trnh dn dng.

Thng 3/1931, SPE v Socit de Recherches Gophysique Minires (SGRM), 2 t chc chuyn

v a chn v thm d t, sp nhp vo La Compagnie Gnrale de Gophysique. SGRM cung cp

5.000.000 franc v CGG 120.000 franc tin vn. Trong c s ca mnh ti 30 rue Fabert, Paris, Conrad

Schlumberger quyt nh chuyn hng kinh doanh di b mt n CGG trong khi SPE gi li

logging. ng thi, Raymond Maillet t SGRM c b nhim lm Ch tch CGG.

Hai nm u tin, vic kinh doanh ca CGG gp nhiu kh khn. Kho st gn b mt (thy

vn, khai thc m v cng trnh dn dng) v thm d du kh l khng gip cng ty pht trin

ngay c trong khong thi gian khi gi du l 10 cent mt thng. Nm 1966, CGG m trung tm x

l d liu a chn u tin ti Massy, France.

b) Veritas DGC

Veritas Energy Services, mt cng ty dch v a vt l, c thnh lp vo nm 1974 ti Calgary, Canada bi Rafael B. Cruz v Associates Ltd. ca David B. Robson.

Trong khi , Digital Consultants Inc. c thnh lp ti Houston, Texas vo nm 1965 vi

tm nhn ng dng tnh ton k thut s cho ngnh cng nghip a vt l. Nm 1969 Digital

Consultants tch hp thnh Digicon Inc. (DGC), tr thnh mt cng ty i chng trn th trng chng

khon M.

Nm 1996, Veritas DGC c hnh thnh t s sp nhp ca Veritas v Digicon.

c) Vic sp nhp v mua li

Trong nm 2007, CGG Veritas mua li DGC v i tn thnh CGGVeritas. CGGVeritas sau mua

li Wavefield Inseis, mt t chc bin Na Uy, trong nm 2009. Trong nm 2013, CGGVeritas mua

li Geoscience Division ca Fugro v li thay i tn l CGG, tr thnh mt cng ty khoa hc minh

gii a cht vi tng s lao ng trn 9.800 ngi lm vic ti hn 70 a im trn khp th gii.

3.1.1.2 Quan h hp tc gia CGG Veritas v PTSC

Ngy 19/4/2011, ti H Ni, Tng cng ty C phn Dch v K thut Du kh Vit Nam (PTSC)

v CGG Veritas ( Php) k hp ng thnh lp Lin doanh khai thc Tu kho st a chn 2D&

3D. Theo ni dung Hp ng lin doanh, PTSC v i tc CGG Veritas hp tc cng thnh lp mt

Lin doanh nhm khai thc cc tu kho st a chn 2D & 3D, c th l cc tu a chn 3D Amadeus

v tu a chn 2D Bnh Minh 02.CGG Veritas. Tham gia lin doanh, PTSC s hu phn gp vn

48.621.360 USD chim 51% vn iu l, CGGV gp 46.714.640 USD chim 49% vn iu l. Trong

, PTSC c phn cng khai thc tu a chn 2D Bnh Minh 02 v h tr cc hot ng ca Lin

doanh.

n ngy 9 /11/2011, Lin doanh chnh thc c cp giy php hot ng vi tn ng k

l Cng ty TNHH Kho st a vt l PTSC CGGV ( PTSC CGGV GEOS Co., Ltd.). Tr s PTSC

CGGV GEOS Co., Ltd c t ti Petro Tower s 08 Hong Diu Tp. Vng Tu.

Vi vic thnh lp Lin doanh ny, PTSC s pht trin thm cng tc a chn 3D trong lnh

vc du kh trong nc v trn th gii. Bn cnh , CGGV s cng PTSC xy dng k hoch o

to v chuyn giao cng ngh t CGGV cho Lin doanh pht trin nng lc ca Lin doanh.

3.1.2 Gii thiu v phn mm Hampson Russell Suite

3.1.2.1 Tng quan

Hampson-Russell l b phn mm cung cp cc dch v a vt l t nm 1987, khi Dan

Hampson v Brian Russell thnh lp cng ty ca mnh ch vi bn nhn vin.

n nay, phn mm ny vn duy tr danh ting trong vic minh gii a chn v c tnh va

cha bng cch cung cp mt b tch hp y cc cng c minh gii a vt l ng cp th gii

cng vi cc dch v t vn ton cu v c tnh va cha. Phn mm ny c tiu ch: an ton hn,

thng minh hn v hiu qu hn.

3.1.2.2 An ton hn

B phn mm Hampson-Russell cung cp dch v minh gii a chn trc quan v nghim ngt, trong

khi nhm cc dch v ca CGG Veritas cung cp cc c tnh va cha cha nghim ngt.

Mng li ton cu v vn phng cung cp cc dch v h tr, o to v t vn gip bn nhn c

nhiu li ch nht t Hampso