11

Chapter 2 Chapter 2

Petroleum Geology and Petroleum Geology and ReservoirsReservoirs

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Petroleum Geology Petroleum Geology (( 石油地質石油地質 ))

Geology (Geology ( 地質地質 )) ------ 研究研究 (1)(1) 地球的歷史及構造地球的歷史及構造 (2)(2) 記錄在岩石的生物記錄在岩石的生物 (( 命命 )) 形式形式

Petroleum Geology(Petroleum Geology( 石油地質石油地質 )) ------ 研究地質以預測石油累積之處所研究地質以預測石油累積之處所

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地球的形成及構造地球的形成及構造 地球的形成 —地球的形成 — 4040 ～～ 5050 億年前由宇宙塵億年前由宇宙塵 (C(C

osmic dust)osmic dust) 的凝結而成的凝結而成

地球內部大構造 —地球內部大構造 — Core--- heavy (4,400 miles)Core--- heavy (4,400 miles) Mantle--- Lighter (1,800 miles)Mantle--- Lighter (1,800 miles) Crust--- 10~30 milesCrust--- 10~30 miles

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地球內部大構造地球內部大構造

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在地球上，不管您走到哪裡，你都是在岩石（ Rock ）的上面。在某些地方，你是站有岩石的上面 20 哩處

20 哩是多少 ?

6MILES = 9.6 KILOMETERS

20MILES = 32 KILOMETERS

喜馬拉雅山大約有 6 哩高

所以 20 哩是喜馬拉雅山的 3 倍高，其間有很多的岩石。

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地球表面的變化 地球表面的變化 -- Rock cycle-- Rock cycle

Magma( 岩漿 )

Igneous rocks( 火成岩 )

Sediments( 沉積物 )

Sedimentaryrocks

Metamorphicrocks

地球內部 Water vapor and gases

Primeval( 初期的 )Atmosphere( 大氣 )

地殼冷卻

地殼收縮變形而皺摺

噴出 形成

heat

heatpressure

erosion

erosion

pressurecementation

erosion

下雨

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Reservoir Rock

Reservoir RockProrsity

Permeability

Sandstones (SiO2)

Carbonates Limestones (CaCO3)

Dolomites (CaCO3, MgCO3)

ClasticClastic ChemicalChemical OrganicOrganic OtherOther

ConglomerateConglomerateSandsonteSandsonteSiltstoneSiltstoneShaleShale

CarbonateCarbonate EvaporiteEvaporite PeatPeatCoalCoalDiatomiteDiatomiteLimestoneLimestone

ChertChert

LimestoneLimestoneDolomiteDolomite

GypsumGypsumAnhydriteAnhydriteSaltSaltPotashPotash

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沉積岩的分類沉積岩的分類

ClasticClastic ChemicalChemical OrganicOrganic OtherOther

ConglomerateConglomerateSandsonteSandsonteSiltstoneSiltstoneShaleShale

CarbonateCarbonate EvaporiteEvaporite PeatPeatCoalCoalDiatomiteDiatomiteLimestoneLimestone

ChertChert

LimestoneLimestoneDolomiteDolomite

GypsumGypsumAnhydriteAnhydriteSaltSaltPotashPotash

碎屑岩碎屑岩 化學岩化學岩 有機岩有機岩 其他其他

礫岩礫岩砂岩砂岩粉砂岩粉砂岩頁岩頁岩

碳酸鹽碳酸鹽 蒸發岩蒸發岩 泥炭泥炭煤煤矽藻土矽藻土石灰岩石灰岩

角岩角岩

石灰岩石灰岩白雲石白雲石

石膏石膏硬石膏硬石膏鹽岩鹽岩碳酸鉀碳酸鉀 ((鉀化鉀化合物合物 ))

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地球的歷史地球的歷史

寒武紀寒武紀 (Cambrian)(Cambrian) 【約【約 5.55.5 億年前】開始在海洋億年前】開始在海洋裡有大量的生物裡有大量的生物 (( 生命生命 ))

在寒武紀之前為前寒武紀在寒武紀之前為前寒武紀 (Precambrian)(Precambrian)

地質年代自寒武紀開始地質年代自寒武紀開始 > > 地質代年表地質代年表 (Geologic Time Scale)(Geologic Time Scale)

泥盆紀泥盆紀 (Devonian)(Devonian) 時期【約時期【約 3.33.3 億年前】陸上有億年前】陸上有大量植物及動物大量植物及動物

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Geological Time ScaleGeological Time Scale

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地層年代表地層年代表

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Petroleum accumulationPetroleum accumulation(( 石油累積石油累積 ))

Petroleum accumulation(Petroleum accumulation( 石油累積石油累積 )) 必須具備必須具備

(1)Oil (1)Oil ＆ ＆ gas gas 之來源之來源 (2)(2) 具有孔隙具有孔隙 (porosity)(porosity) 及滲透率及滲透率 (permeability)(permeability)

之之 Reservoir RockReservoir Rock (3) (3) 要有要有 trap(trap( 封閉封閉 )) 以阻擋流體的流動以阻擋流體的流動

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石油的來源石油的來源

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含石油的岩石都是由很小顆粒的砂、淤泥或泥土開始的，就如同地上的土壤

經過多年的風吹雨打，這些土壤流到低窪處而停下來。

通常，這些低窪處是水底、河底、湖底或海底。

，

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砂、淤泥，泥土的顆粒沉到水裡，蓋在死的矽藻類以及其他的動植物之上。而且，水被夾在這些砂、淤泥及泥土的顆粒之中。

不久，這些顆粒，又被其他的動植物殘骸覆蓋。這個過程，一再的重複，最後，泥、砂及水累積達幾千呎厚。

這些砂、泥在堆積過程中，底部的砂、泥受到上部砂、泥而擠壓

在河流、湖及海底的泥、砂、水及動植物殘骸所受的覆蓋壓力逐漸的變大

當覆蓋深度加大越深，其溫度也增加。經過幾百萬年之後，在適當的壓力及溫度之下，這些泥砂顆粒就變硬而變成岩石，類似褐色或灰色的水泥。

當動植物的殘骸腐朽之後，形成石油及天然氣，大部分的石油及天然氣係由相當微小的動植物殘骸而來的

確認的石油及天然氣之形成原因仍不清楚。但是，溫度、壓力及細菌是很重要的因素。

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石油的來源石油的來源

－石油來自沈積岩的有機物質－石油來自沈積岩的有機物質 －海洋裡大量的生物不停的，緩慢的掉落到海底。－海洋裡大量的生物不停的，緩慢的掉落到海底。 雖然在掉落的過程中，有部分被吃掉或被氧化掉，雖然在掉落的過程中，有部分被吃掉或被氧化掉， 但另部份但另部份 (( 動物或植物動物或植物 )) 掉落海底而埋在沼澤或泥濘之掉落海底而埋在沼澤或泥濘之 海底海底 －海底繼續被－海底繼續被 Sand(Sand( 砂砂 )) ，， Clay(Clay( 黏土黏土 )) 及及 debrisdebris 等沈積等沈積

物埋沒物埋沒 一直到幾千英呎一直到幾千英呎 －沈積物的壓力開始作用。－沈積物的壓力開始作用。 細菌由殘餘的有機物質中，用掉氧而分解物質，細菌由殘餘的有機物質中，用掉氧而分解物質， 使其僅存碳及氫使其僅存碳及氫 －在高度的壓力及重量的地層影響之下，－在高度的壓力及重量的地層影響之下， ClaysClays 變成變成 Shales → Shales → 石油產生石油產生

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Petroleum formation requires Petroleum formation requires that organic source clays that organic source clays become mature by subjection to become mature by subjection to pressure and temperature.pressure and temperature.

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石油形成的重要條件石油形成的重要條件

225℉ < temperature < 350℉ 225℉ < temperature < 350℉ 有利條件有利條件

temperature < 150℉ temperature < 150℉ 不可能形成石油不可能形成石油

temperature > 500℉ temperature > 500℉ 有機物質碳化，有機物質碳化， 不能形成石油不能形成石油

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Generation of gas and oilGeneration of gas and oil

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In In geologygeology and and oceanographyoceanography, , diagenesdiagenesisis is any chemical, physical, or biological is any chemical, physical, or biological change undergone by a change undergone by a sedimentsediment after it after its initial deposition and during and after is initial deposition and during and after its ts lithificationlithification, exclusive of surface alter, exclusive of surface alteration (weathering) and ation (weathering) and metamorphismmetamorphism. .

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CatagenesisCatagenesis can refer to: can refer to: Catagenesis (geology)Catagenesis (geology) – The – The crackingcracking pr pr

ocess in which organic ocess in which organic kerogenskerogens are bro are broken down into ken down into hydrocarbonshydrocarbons; ;

Catagenesis (biology)Catagenesis (biology) – Retrogressive ev – Retrogressive evolution, as contrasted with olution, as contrasted with anagenesisanagenesis. .

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MetamorphismMetamorphism can be defined as the so can be defined as the solid state recrystallisation of pre-existing lid state recrystallisation of pre-existing rocksrocks due to changes in heat and/or pre due to changes in heat and/or pressure and/or introduction of fluids i.e wissure and/or introduction of fluids i.e without melting. There will be thout melting. There will be mineralogicmineralogicalal, chemical and , chemical and crystallographiccrystallographic chang changes es

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Prolonged exposure to high temperatures, or shorter Prolonged exposure to high temperatures, or shorter exposure to very high temperatures, may lead progresexposure to very high temperatures, may lead progressively to the generation of hydrocarbon mixtures charsively to the generation of hydrocarbon mixtures characterized as condensates, wet gases and gas.acterized as condensates, wet gases and gas.

The average organic content of potential source rocks The average organic content of potential source rocks is about 1% by weight.is about 1% by weight.

The Kimmeridge clay, the principal source rock for NorThe Kimmeridge clay, the principal source rock for North Sea oil average about 5% carbon (~7% organic matth Sea oil average about 5% carbon (~7% organic mater) with local rich streaks greater than 40%.er) with local rich streaks greater than 40%.

The hydrogen content of the organic matter should be The hydrogen content of the organic matter should be greater than 7% by weight for potential as an oil sourcgreater than 7% by weight for potential as an oil source.e.

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It is a rule of thumb that for each It is a rule of thumb that for each percentage point of organic carbon in percentage point of organic carbon in mature source rocks, some mature source rocks, some 1300~1500 cubic meters of oil per 1300~1500 cubic meters of oil per kmkm22-m (or 10~40 barrels of oil per -m (or 10~40 barrels of oil per acre-ft; or 56-225 ftacre-ft; or 56-225 ft3/ 43560 ft/ 43560 ft3) of ) of sediment could be generated.sediment could be generated.

It is not, however, necessarily true It is not, however, necessarily true that all the oil generated will be that all the oil generated will be expelled or trapped in porous rock.expelled or trapped in porous rock.

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石油移棲石油移棲

石油形成後 Traps ＆ Reservoir RocksMigration

經過 porous bed 有 permeability

由於 Compaction of Source bed

The migration process involves two main stages, The migration process involves two main stages, namely from the source rock and then through a namely from the source rock and then through a permeable system.permeable system.

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Migration of petroleum Migration of petroleum -- -- from the source rockfrom the source rock

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當石油形成後，它們並不會停留在原地，就如同您我一樣，會搬遷及旅遊

它們到哪裡去 ?

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它們向上移動，有時候通過地球的斷裂地層（稱為斷層， Faults ）

沿著斷層而到達地面的石油及天然氣稱為滲流（ Seep ），在加州有幾百處的滲流，大都是在油、氣田的附近

Jack ，你剛才所踩到的是自然滲流

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印地安人及其拓荒者，利用滲出的石油做很多用途：例如，籃子的防水，馬車的潤滑等。

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大部分的石油及天然氣在到達地表之前遇到無滲透率的的岩層（稱為蓋岩， Cap Rock ）或其他的障礙層，而陷在地層裡。

當很多的石油積集在蓋岩（ Cap Rock ）或其他障礙物下的地層時，就形成了儲石油及天然氣層（ Oil and Gas Reservoirs ）

典型的儲石油及天然氣層（ Oil and Gas Reservoirs ）是在砂粒層，稱為砂岩（ Sandstone ），石油、天然氣及水是夾在砂粒與砂粒間的小空間裏，而不是在一個很大而寬廣之池塘。

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Migration of petroleum Migration of petroleum

-- -- from the source rockfrom the source rock ** Capillary effect** Capillary effect

** Microfractures ** Microfractures Since the generation of petroleum is accompanied bSince the generation of petroleum is accompanied b

y volume changes which can lead to high local pressuy volume changes which can lead to high local pressures, there may well be an initiation of microfractures res, there may well be an initiation of microfractures which provide an escape route into permeable systemwhich provide an escape route into permeable systems such as sedimentary rocks or fault planes.s such as sedimentary rocks or fault planes.

The source rock microfractures are believed to heal aThe source rock microfractures are believed to heal as pressures are dissipated.s pressures are dissipated.

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Migration of petroleum Migration of petroleum ----through a permeable systemthrough a permeable system

** Fluid potential gradient or gravity effect** Fluid potential gradient or gravity effect In the permeable system the transport occurs uIn the permeable system the transport occurs u

nder conditions of a fluid potential gradient wnder conditions of a fluid potential gradient which may take the hydrocarbon to surface or thich may take the hydrocarbon to surface or to some place where it becomes trapped.o some place where it becomes trapped.

It might be assumed that less than 10% of petrIt might be assumed that less than 10% of petroleum generated in source rocks is both expelloleum generated in source rocks is both expelled and trapped, as shown in the example of Fied and trapped, as shown in the example of Fig. 2.5. g. 2.5.

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Petroleum traps(Petroleum traps( 石油封閉石油封閉 )) The characteristic forms of petroleum trThe characteristic forms of petroleum tr

ap are known as ap are known as

structural traps(structural traps( 構造封閉構造封閉 ) and ) and stratigraphic traps(stratigraphic traps( 地層封閉地層封閉 ),), with the great majority of known accumuwith the great majority of known accumu

lation being in the former style.lation being in the former style.

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地質構造（地質構造（ Geological StructuresGeological Structures ））

Erosion － SedimentationUplift － wearing down

Upper crust moveUpward

downward

Fault

Normal

Reverse

Thrust

Lateral

Strata or bed Unconformity－ disconformity－ Angular unconformity

FoldsArches (or upfold) → anticlines

Traughs (or downfold) → synclines

Important to petroleum accumulation

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Figure 1.12. Two general kinds of unconformities are disconformity (A) and angular unconformities (B) and (C).

造山運動之應力所造成

沉積過程所造成

Figure 1.13. Basic hydrocarbon reservoirs are structural and / or stratigraphic traps.

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封閉 (traps)

封閉 (traps)Structural traps － an arched upper surfaceStratigraphic traps---up-dip termination of porosity (permeability)

Structural traps

Anticline trapFault trapDome and plug trap

Stratigraphic traps

Unconformity trapsLenticular trap

Disconformity

Angular unconformity

Combination traps

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Cap rockCap rock

Impermeable rocks provide seal above Impermeable rocks provide seal above and below the permeable reservoir rockand below the permeable reservoir rocks.s.

At equilibrium conditions, the density difAt equilibrium conditions, the density dif

ferences between the oil, gas and water ferences between the oil, gas and water phases can result in boundary regions bphases can result in boundary regions between them known as fluid contacts, i.etween them known as fluid contacts, i.e. gas-oil and oil-water contacts.e. gas-oil and oil-water contacts.

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Structural trapa( 構造封閉構造封閉 )) -- AnticlineAnticline

Longitudinal view of a typical anticline. The oil cannot escape upward because of the impervious shale bed above the oil sand; neither can it travel downward because of the water that is associated with an accumulation of this type.

Anticlines －Of the many types of structural features present in the upper layers of the earths crust that can trap oil, the most important is the anticlines－ the type of structure from which the greater part of the word’s oil has been produced. Anticlines are upfolds of beds in the earth’s crust, and, when the proper conditions are present, oil accumulates within the closure of there folds.

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Structural trap-- Anticline Anticline

Lateral, or end view, of a typical anticline.

Plan view of a typical anticline, showing locations of longitudinal view A-B and lateral view C-D.

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Structural trapsFigure 1.7. Schematic cross section shows deformation of earth’s crust by bucking of layers into folds

Figure 1.8. Simple kinds of folds are symmetrical anticline (A), plunging asymmetrical anticline (B), plunging syncline (C), and dome with deep salt core (D).

Figure 1.9. Simplified diagram of the Milano, Texas, fault.

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Structural traps– dome & anticline

Figure 1.15. Oil accumulates in a dome-shaped structure (A) and an anticlinal type of fold structure (B). An anticline is generally long and narrow while the dome is circular in outline. (Courtesy of American Petroleum Institute)

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Structural traps -- faultsFigure 1.10. Simple kinds of faults are normal (A), reverse (B), thrust (C), and lateral (D).

Figure 1.11. Variations of normal and reverse faulting are rotational faults (A) and upthrust faults (B).

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Structural traps

Figure 1.14. Common types of structural traps

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Structural trap – fault & anticline

Figure 1.17. Shown in map view, fault traps may be simple (A) or compound (B).

Figure 1.16. Gas and oil are trapped in a fault trap-a reservoir resulting from normal faulting or offsetting of strata. The block on the right has moved up from the block on the left, moving impervious shawl opposite the hydrocarbon-bearing formation. (Courtesy of American Petroleum Institute)

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Stratigraphic trapsStratigraphic traps(( 地層封閉地層封閉 ))

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Figure 1.12. Two general kinds of unconformities are disconformity (A) and angular unconformities (B) and (C).

造山運動之應力所造成

沉積過程所造成

Figure 1.13. Basic hydrocarbon reservoirs are structural and / or stratigraphic traps.

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Stratigraphic trapsStratigraphic traps

Unconformity － Disconformity － Angnlar unconformity Pinctout

Sand lenses

Changes in sedimentation

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Figure 1.22. Oil is trapped under an unconformity. (Courtesy of API)

Figure 1.23. Lenticular traps confine oil in porous parts of the rock. (Courtesy of API)

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Stratigraphic trapStratigraphic trap

An example of a stratigraphic trap where the oil zone pinches out.

A stratigraphic trap where sand lenses are interspersed in a shale bed. The shale acts as a permeability barrier

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Stratigraphic TrapsStratigraphic Traps

A stratigraphic trap where changes in sedimentation act as a permeability barrier.

An angular unconformity as an oil trap. The flat-lying shale bed above the oil zones acts as a permeability barrier.

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Stratigraphic trapsStratigraphic traps

Stratigraphic Stratigraphic traps result traps result when a when a depositional depositional bed changes bed changes from permeable from permeable rock into fine-rock into fine-grain grain impermeable impermeable rock (Fig. 2.8).rock (Fig. 2.8).

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Combination trapsCombination traps

Many reservoirs exist as the result of a cMany reservoirs exist as the result of a combination of structural and stratigraphombination of structural and stratigraphic features.ic features.

In the Viking Graben area of the northern In the Viking Graben area of the northern North Sea, the Brent Sand reservoirs are North Sea, the Brent Sand reservoirs are characteristically faulted deltaic sands tcharacteristically faulted deltaic sands truncated by the Cretaceous unconformitruncated by the Cretaceous unconformity.y.

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ReservoirsReservoirs

Reservoir(Reservoir( 儲油層儲油層 ))

We may define a reservoir as an accumulation of hydrWe may define a reservoir as an accumulation of hydrocarbon in porous permeable sedimentary rock.ocarbon in porous permeable sedimentary rock.

The accumulation, which will have reached a fluid preThe accumulation, which will have reached a fluid pressure equilibrium throughout its pore volume at the tissure equilibrium throughout its pore volume at the time of discovery, is also sometimes known as a pool.me of discovery, is also sometimes known as a pool.

A hydrocarbon field may comprise several reservoirs aA hydrocarbon field may comprise several reservoirs at different stratigraphic horizons or in different pressut different stratigraphic horizons or in different pressure regimes. re regimes.

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FieldField

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LeaseLease

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Reservoir(Reservoir( 儲油層儲油層 ))

具有商業價值的石油具有商業價值的石油 (( 及天然氣及天然氣 )) 地層地層 --reservoi--reservoirr ，所需具備之條件，所需具備之條件

(1)(1)合適之地層形貌 合適之地層形貌 (Shape/Configuration- tra(Shape/Configuration- traps)ps)

(2)(2)頂蓋層 頂蓋層 (cap rock, rock seal)(cap rock, rock seal) (3)(3)儲油層之面積儲油層之面積 (area)(area) 大大 (4)(4)儲油層之厚度儲油層之厚度 (thickness)(thickness) 大大 (5)(5)儲油層之孔隙率儲油層之孔隙率 (porosity)(porosity) 大大 (6)(6)儲油層之含水飽和度儲油層之含水飽和度 (water saturation)(water saturation)小小 (7)(7)儲油層之滲透率儲油層之滲透率 (permeability)(permeability) 大大

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原油現地藏量原油現地藏量Original oil in place (OOIP)Original oil in place (OOIP)

OOIP = A * h * OOIP = A * h * * (1-S * (1-Sww)* 1/B)* 1/Boo

wherewhere A=A= 儲油層之面積儲油層之面積 (area)(area) h=h= 儲油層之厚度儲油層之厚度 (thickness)(thickness) == 儲油層之孔隙率儲油層之孔隙率 (porosity)(porosity) SSww = = 儲油層之含水飽和度儲油層之含水飽和度 (water saturation)(water saturation) Bo = Bo = 石油地層體積因子石油地層體積因子 (oil formation(oil formation volume factor)volume factor)

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原油現地藏量原油現地藏量Original oil in place (OOIP)Original oil in place (OOIP)

OOIP = 7758* A * h * OOIP = 7758* A * h * * (1-S * (1-Sww)* 1/B)* 1/Boo

wherewhere OOIP = OOIP = 原油現地藏量原油現地藏量 , STB, STB A=A= 儲油層之面積儲油層之面積 (area), acres(area), acres h=h= 儲油層之厚度儲油層之厚度 (thickness), ft(thickness), ft == 儲油層之孔隙率儲油層之孔隙率 (porosity), fraction(porosity), fraction SSww = = 儲油層之含水飽和度儲油層之含水飽和度 (water saturation), fraction(water saturation), fraction BBoo = =石油地層體積因子石油地層體積因子 (oil formation volume factor) (oil formation volume factor) , bbl/STB, bbl/STB

1 acres = 43560 ft1 acres = 43560 ft22

1 bbl = 5.61458 ft1 bbl = 5.61458 ft33

6666

資源量及蘊藏量定義資源量及蘊藏量定義

資源量資源量 (Petroleum Resources(Petroleum Resources ， 或 ， 或 ResourcesResources ， 或 ， 或 Total PetrolTotal Petrol

eum in place eum in place ， 或 ， 或 Original oil in place Original oil in place )) 在一區域或礦區所存在的石油（含天然氣）之總在一區域或礦區所存在的石油（含天然氣）之總量，稱為資源量。量，稱為資源量。

蘊藏量蘊藏量 (Petroleum Reserves(Petroleum Reserves ，或 ，或 Reserves )Reserves )

在一已知區域或礦區中，自某一時間點開始，依在一已知區域或礦區中，自某一時間點開始，依據當時的經濟條件據當時的經濟條件 (E)(E) 、工程技術、工程技術 (F)(F) 、及地質、及地質條件條件 (G)(G) 下，在可預見的未來所能採收的石油下，在可預見的未來所能採收的石油（含天然氣）之量稱為蘊藏量，或最終採收量。（含天然氣）之量稱為蘊藏量，或最終採收量。

6767

Reserves (Reserves ( 蘊藏量蘊藏量 )) Reserves = OOIP * recovery factorReserves = OOIP * recovery factor

where OOIP = A * h * where OOIP = A * h * * (1-S * (1-Sww) * 1/B) * 1/Boo

recovery factor (recovery factor ( 採收因子採收因子 ) ) = f( k, E, P, T …)= f( k, E, P, T …) k = permeability (k = permeability ( 滲透率滲透率 ))

6868

The setting for hydrocarbon accumulation The setting for hydrocarbon accumulation

is a sedimentary basin that has provided is a sedimentary basin that has provided the essential components for petroleum the essential components for petroleum reservoir occurrence, namelyreservoir occurrence, namely (a) a source for hydrocarbons, (a) a source for hydrocarbons, (b) the formation and migration of petroleum,(b) the formation and migration of petroleum, (c) a trapping mechanism, i.e., the existence of (c) a trapping mechanism, i.e., the existence of

traps in porous sedimentary rock at the time of traps in porous sedimentary rock at the time of migration and in the migration path.migration and in the migration path.

The discovery of oil by exploration well The discovery of oil by exploration well drilling in some of the world’s sedimentary drilling in some of the world’s sedimentary basin is shown in Figs. 2.1 and 2.2basin is shown in Figs. 2.1 and 2.2

6969

7070

Lower right line (0.1 103 m3 oil / km2 ) / (100 willcat wells/104 km2 ) = 104 m3 oil / willcat well = 6.289*104 bbl3 oil / willcat well

Upper left line (10 103 m3 oil / km2 ) / (1 willcat well/104 km2 ) = 108 m3 oil / willcat well = 6.289*108 bbl oil / willcat well

7171

7272

Lower right line (0.01 106 m3 oil discovered / willcat ) / (1 106 m3 oil discovered/ successful wildcat ) = 1% successful wildcat / willcat

Upper left line (0.1 106 m3 oil discovered / willcat ) / (0.1 106 m3 oil discovered/ successful wildcat ) = 100% successful wildcat / willcat

7373

現今的石油鑽井很安全；很多國家都有制定法令以保護地表及地下之自然環境。

在七個探勘井中會有一口具有生產利潤的生產井

對於不具生產價值的井，必須用水泥及泥土將井口封閉起來

7474

7575

Reservoir fluids and pressureReservoir fluids and pressure

From a petroleum engineering From a petroleum engineering perspective it is convenient to think perspective it is convenient to think of sedimentary basins as of sedimentary basins as accumulations water in areas show accumulations water in areas show subsidence into which sediments subsidence into which sediments have been transported.have been transported.

7777

Reservoir fluids and pressureReservoir fluids and pressure

Reservoir fluidsGasOilwater

Water ─ connate water(connate interstitial water)

Free water~Aquifer

Bottom water

Edge water

Gas Solution gas

Free gas

7878

7979

Pressure Kick – Oil and Water

8080

pressure kick-gas and water

8181

pressure kick-gas, oil and water

8282

Pressure Kick – Oil and WaterP(psia)

5000

5200

55005600

oil

water

OWCD=5500ft

Pw=2265 Po=2315

Pw=2355 Po=2385

Pw=Po=2490Pw=2535

Depth(ft)

psia 2265 155000*45.0)5000 (psia 2315 5655000*35.0)5000 (

psia 2355 155200*45.0)5200 (psia 23856555200*35.0)5200 (

zone oilin 565D*0.35P5655500*0.35-2490Cor

*35.0 2490) 5500 (

psia 2490 155500*45.0) 5500 (psia 2535 155600*45.0)5600 (

][ 15*45.0

o

o

ftDatPftDatPftDatPftDatP

CDOWCatorftDatPOWCatorftDatP

ftDatPzonewaterinpsiaDP

w

o

w

o

o

o

w

w

w

8383

pressure kick-gas and water

psiaftDatP

psiaftDatP

psiaftDatP

psiftDatP

zonegasinDP

Cor

CD

GWCftDatP

psiaGWCftDatP

psiaftDatP

zonewaterinDP

w

g

w

g

g

g

g

g

w

w

w

2265)5000(

245020505000*08.0)5000(

2355)5200(

246620505200*08.0)5000(

2050*08.0

20505500*08.02490

*08.0

2490)5500(

2490)5500(

2535)5600(

15*45.0

Gas

P(psia)5000

5200

55005600

Pw=2265 Pg=2450

Pg=2466Pw=2355

Pw=Pg=2490Pw=2535

Depth(ft)

GWC

water

D=5500ft

8484

pressure kick-gas, oil and water

psiaftDatp

psiaftDatp

zoneoilinDp

Cor

CD

psiaOWCftDatp

psiaOWCftDatp

psiftDatp

zonewaterinDp

w

o

o

o

o

o

w

w

w

2445155400*45.0)5400(

24555655400*35.0)5400(

565*35.0

565

*35.0

2490)5500(

2490)5500(

2535)5600(

15*45.0

psiaftDatp

psiaftDatp

psiaftDatp

psiaftDatp

Dp

Cor

CD

psiaGOCftDatpGOCftDatp

psiaGOCftDatp

psiaGOCftDatp

w

g

w

g

g

g

g

go

w

o

2265)5000(

239619965000*08.0)5000(

2355)5200(

241219965200*08.0)5200(

1996*08.0

1996

*08.0

2420)5300()5300(

2400155300*45.0)5300(

24205655300*35.0)5300(

P(psia)5000

52005300540055005600

Pw=2265 Pg=2396

Pw=2355 Pg=2412Pw=2400 Po =Pg=2420

Pw=2445 Po=2455Pw= Po=2490

Pw=2535

Depth(ft)

Gas

GOC

oilOWC

water

D=5500ft

D=5300ft

8585

Fluid pressures in a hydrocarbon Fluid pressures in a hydrocarbon zonezone

Pressure gradient equationPressure gradient equation

In a water column representing vertical pore fluid conIn a water column representing vertical pore fluid continuity, the pressure at any point (Ptinuity, the pressure at any point (Pxx) is approximated ) is approximated by the relationshipby the relationship

PPxx = X = X ．． GGww

where X = the depth below a reference datum (such where X = the depth below a reference datum (such as sea level)as sea level) GGww = the pressure exerted by unit height of = the pressure exerted by unit height of water, or pressure gradientwater, or pressure gradient GGww = f (T, salinity) = f (T, salinity) GGww = 0.433 psi/ft (or 9.79 kpa/m) for fresh water = 0.433 psi/ft (or 9.79 kpa/m) for fresh water GGww = 0.44 psi/ft (10 kpa/m) ~ 0.53 psi/ft (12 kpa/m) = 0.44 psi/ft (10 kpa/m) ~ 0.53 psi/ft (12 kpa/m) for reservoir water system for reservoir water system

8787

Hydrocarbon pressure regimesHydrocarbon pressure regimes

In hydrocarbon pressure regimesIn hydrocarbon pressure regimes

psi/ftpsi/ft

psi/ftpsi/ft

psi/ft psi/ft

45.0)( waterdD

dP

35.0)( oildD

dP

08.0)( gasdD

dP

Pressure gradient rangesPressure gradient ranges

In reservoir found at depth between 2000 m In reservoir found at depth between 2000 m SS and 4000 m SS, we might use a gradient of SS and 4000 m SS, we might use a gradient of 11 kpa/m to predict pore fluid pressures arou11 kpa/m to predict pore fluid pressures around 220 bars to 440 bars. nd 220 bars to 440 bars.

Reservoir pressuresReservoir pressures

Hydrocarbon reservoirs are found over a wide Hydrocarbon reservoirs are found over a wide range of present day depths of burial, the majrange of present day depths of burial, the majority being in the range 500 – 4000 m ss.ority being in the range 500 – 4000 m ss.

In our concept of the petroliferous sedimentarIn our concept of the petroliferous sedimentary basin as a region of water into which sedimey basin as a region of water into which sediment has accumulated and hydrocarbons have bnt has accumulated and hydrocarbons have been generated and trapped, we may have an eeen generated and trapped, we may have an expectation of regional hydrostatic gradient.xpectation of regional hydrostatic gradient.

9090

Reservoir pressure

Reservoir pressureNormal pressure

Abnormal pressure － Artesian effect

9191

9292

The primary depositional processes and The primary depositional processes and the nature of the sediments have a majothe nature of the sediments have a major influence on the porosity and permeabr influence on the porosity and permeability of reservoir rocks.ility of reservoir rocks.

9393

Secondary processes, including compaction, sSecondary processes, including compaction, s

olution, chemical replacement and diagenetic olution, chemical replacement and diagenetic changes, can act to modify further the pore strchanges, can act to modify further the pore structure and geometry. ucture and geometry.

With compaction, grains of sediment are subjeWith compaction, grains of sediment are subject to increasing contact and pore fluids may bct to increasing contact and pore fluids may be expelled from the decreasing pore volume. If e expelled from the decreasing pore volume. If the pore fluids cannot be expelled, the pore fluthe pore fluids cannot be expelled, the pore fluid pressure may increase.id pressure may increase.

Abnormal pressureAbnormal pressure

Under certain depositional conditions, or becaUnder certain depositional conditions, or because of movement of closed reservoir structureuse of movement of closed reservoir structures, fluid pressures may depart substantially fros, fluid pressures may depart substantially from the normal range.m the normal range.

One particular mechanism responsible for overOne particular mechanism responsible for overpressure in some North Sea reservoirs is the inpressure in some North Sea reservoirs is the inability to expel water from a system containinability to expel water from a system containing rapidly compacted shales.g rapidly compacted shales.

Abnormal pressure regimes are evident in Fig. Abnormal pressure regimes are evident in Fig. 2.11.2.11.

Abnormal high pressureAbnormal high pressure

All show similar salinity gradients but All show similar salinity gradients but different degrees of overpressure, possibly different degrees of overpressure, possibly related to development in localized basins.related to development in localized basins.

Any hydrocarbon bearing structure of Any hydrocarbon bearing structure of substantial relief will exhibit abnormally substantial relief will exhibit abnormally high pressure at the crest when the high pressure at the crest when the pressure at the hydrocarbon-water contact pressure at the hydrocarbon-water contact is normal, simply because of the lower is normal, simply because of the lower density of the hydrocarbon compared with density of the hydrocarbon compared with water. water.

9797

2.3 Fluid pressures in a hydrocarbon 2.3 Fluid pressures in a hydrocarbon zonezone

9898

9999

Are the water bearing sands abnormally Are the water bearing sands abnormally pressured ?pressured ?

If so, what effect does this have on the If so, what effect does this have on the

extent of any hydrocarbon extent of any hydrocarbon accumulations?accumulations?

100100

Pressure KickPressure Kick

Assumes a normal hydrostatic pressure regime Pω= 0.45 × D + 15Assumes a normal hydrostatic pressure regime Pω= 0.45 × D + 15 In water zoneIn water zone at 5000 ft Pω(at5000) = 5000 × 0.45 + 15 = 2265 psiaat 5000 ft Pω(at5000) = 5000 × 0.45 + 15 = 2265 psia at OWC (5500 ft) Pω(at OWC) = 5500 × 0.45 + 15 = 2490 psiaat OWC (5500 ft) Pω(at OWC) = 5500 × 0.45 + 15 = 2490 psia

101101

Pressure KickPressure Kick

In oil zone Po = 0.35 x D + C In oil zone Po = 0.35 x D + C at D = 5500 ft , Po = 2490 psi at D = 5500 ft , Po = 2490 psi → → C = 2490 – 0.35 × 5500 = 565 psiaC = 2490 – 0.35 × 5500 = 565 psia → → Po = 0.35 × D + 565Po = 0.35 × D + 565 at GOC (5200 ft) Po (at GOC) = 0.35 × 5200 + 565 = 2385 psiaat GOC (5200 ft) Po (at GOC) = 0.35 × 5200 + 565 = 2385 psia

102102

Pressure KickPressure Kick

In gas zone Pg = 0.08 D + 1969 (psia)In gas zone Pg = 0.08 D + 1969 (psia) at 5000 ft Pg = 0.08 × 5000 + 1969 = 2369 psia at 5000 ft Pg = 0.08 × 5000 + 1969 = 2369 psia

103103

Pressure KickPressure Kick

In gas zone Pg = 0.08 D + CIn gas zone Pg = 0.08 D + C At D = 5500 ft, Pg = Pω = 2490 psiaAt D = 5500 ft, Pg = Pω = 2490 psia 2490 = 0.08 × 5500 + C2490 = 0.08 × 5500 + C C = 2050 psiaC = 2050 psia → → Pg = 0.08 × D + 2050Pg = 0.08 × D + 2050 At D = 5000 ftAt D = 5000 ft Pg = 2450 psiaPg = 2450 psia

Overburden pressureOverburden pressure

There is a balance in a reservoir system betweThere is a balance in a reservoir system between the pressure gradients representing rock oven the pressure gradients representing rock overburden (Gerburden (Grr), pore fluids (G), pore fluids (Gff) and sediment gr) and sediment grain pressure (Gain pressure (Ggg).).

The pore fluids can be considered to take part The pore fluids can be considered to take part of the overburden pressure and relieve that paof the overburden pressure and relieve that part of the overburden load on the rock grains.rt of the overburden load on the rock grains.

GGrr =G =Gff + G + Ggg

Overburden gradientOverburden gradient

The magnitude of the overburden gradieThe magnitude of the overburden gradient is approximately 1 psi/ft (22.6 kpa/m).nt is approximately 1 psi/ft (22.6 kpa/m).

For 100% rock (sand) GFor 100% rock (sand) Ggg = 0.433 x 2.7 = 1.169 psi/ft = 0.433 x 2.7 = 1.169 psi/ft For 100% water GFor 100% water Gff = 0.433 psi/ft = 0.433 psi/ft For For =20% rock G =20% rock Grr = 0.2 x 0.433 +0.8 x 1.169 = 0.2 x 0.433 +0.8 x 1.169 = 1.022 psi/ft= 1.022 psi/ft

Causes of abnormal pressureCauses of abnormal pressure

Abnormal fluid pressures are those not in Abnormal fluid pressures are those not in initial fluid equilibrium at the discovery depth.initial fluid equilibrium at the discovery depth.

Magara (1978) has described conditions Magara (1978) has described conditions leading to abnormally high and abnormally leading to abnormally high and abnormally low pressures. Some explanations lie in low pressures. Some explanations lie in reservoirs being found at pressure depths reservoirs being found at pressure depths higher or lower than the depths at which they higher or lower than the depths at which they became filled with hydrocarbon. This may be became filled with hydrocarbon. This may be the result of upthrust or downthrown faulting.the result of upthrust or downthrown faulting.

Causes of abnormal pressureCauses of abnormal pressure

Overpressure from the burial weight of gOverpressure from the burial weight of glacial ice has also been cited.lacial ice has also been cited.

In Gulf coast and North Sea reservoirs, oIn Gulf coast and North Sea reservoirs, overpressure is most frequently attributeverpressure is most frequently attributed to rapid deposition of shales from whid to rapid deposition of shales from which bound water cannot escape to hydroch bound water cannot escape to hydrostatic equilibrium. This leads to overpresstatic equilibrium. This leads to overpressured aquifer-hydrocarbon system.sured aquifer-hydrocarbon system.

Fluid Pressure RegimesFluid Pressure Regimes

The total pressure at any depth The total pressure at any depth = weight of the formation rock = weight of the formation rock + weight of fluids (oil, gas or water)+ weight of fluids (oil, gas or water)

[=] 1 psi/ft * depth(ft)[=] 1 psi/ft * depth(ft)

Fluid Pressure RegimesFluid Pressure Regimes

Density of sandstone Density of sandstone

3

3

3 )1(

)1003048.0(

1000

2.27.2

ft

cm

gm

lbm

cm

gm

lbm

slug

ft

lb

7.32

1202.168

3

322.5

ft

slug

Pressure gradient for sandstonePressure gradient for sandstone

Pressure gradient for sandstonePressure gradient for sandstone

gD

p

gDp

3084.1682.3222.5

ft

lbf

)/(16.1144

1084.168

22

2

2ftpsi

ftin

lbf

in

ft

ftft

lbf

Overburden pressureOverburden pressure Overburden pressure (OP)Overburden pressure (OP) = Fluid pressure (FP) + Grain or matrix pressure(GP)= Fluid pressure (FP) + Grain or matrix pressure(GP) OP=FP + GPOP=FP + GP

In non-isolated reservoir In non-isolated reservoir PW (wellbore pressure) = FPPW (wellbore pressure) = FP

In isolated reservoir In isolated reservoir PW (wellbore pressure) = FP + GP’PW (wellbore pressure) = FP + GP’ where GP<=GPwhere GP<=GP

In a perfectly normal case , the water pressure at any depth In a perfectly normal case , the water pressure at any depth

Normal hydrostatic pressureNormal hydrostatic pressure

In a perfectly normal case , the water pressure at any dIn a perfectly normal case , the water pressure at any depthepth

Assume :(1) Continuity of water pressure to the surfaceAssume :(1) Continuity of water pressure to the surface (2) Salinity of water does not vary with depth.(2) Salinity of water does not vary with depth. [=] psia [=] psia

psi/ft for pure waterpsi/ft for pure water psi/ft for saline waterpsi/ft for saline water

7.14)( DdD

dPP water

4335.0)( waterdD

dP

4335.0)( waterdD

dP

Abnormal hydrostatic pressure Abnormal hydrostatic pressure ( No continuity of water to the surface)( No continuity of water to the surface)

[=] psia[=] psia

Normal hydrostatic pressureNormal hydrostatic pressure c = 0 c = 0

Abnormal (hydrostatic) pressureAbnormal (hydrostatic) pressure c > 0 → Overpressure (Abnormal high pressure)c > 0 → Overpressure (Abnormal high pressure) c < 0 → Underpressure (Abnormal low pressure)c < 0 → Underpressure (Abnormal low pressure)

CDdD

dPP water 7.14)(

Conditions causing abnormal fluid Conditions causing abnormal fluid pressurespressures

Conditions causing abnormal fluid pressures in enclosConditions causing abnormal fluid pressures in enclosed water bearing sands includeed water bearing sands include

Temperature change ΔT = +1℉ → ΔP = +125 psi in Temperature change ΔT = +1℉ → ΔP = +125 psi in a sealed fresh water systema sealed fresh water system

Geological changes – uplifting; surface erosionGeological changes – uplifting; surface erosion Osmosis between waters having different salinity, Osmosis between waters having different salinity,

the sealing shale acting as the semi permeable methe sealing shale acting as the semi permeable membrane in this ionic exchange; if the water within tmbrane in this ionic exchange; if the water within the seal is more saline than the surrounding water the seal is more saline than the surrounding water the osmosis will cause the abnormal high pressure he osmosis will cause the abnormal high pressure and vice versa.and vice versa.

GWC error from pressure measurementGWC error from pressure measurement Pressure = 2500 psia Pressure = 2450 psia Pressure = 2500 psia Pressure = 2450 psia at D = 5000 ft at D = 5000 ftat D = 5000 ft at D = 5000 ft in gas-water reservoir in gas-water reservoirin gas-water reservoir in gas-water reservoir GWC = ? GWC = ?GWC = ? GWC = ? Sol. Sol.Sol. Sol. Pg = 0.08 D + C Pg = 0.08 D + CPg = 0.08 D + C Pg = 0.08 D + C C = 2500 – 0.08 × 5000 C = 2450 – 0.08 × 5000C = 2500 – 0.08 × 5000 C = 2450 – 0.08 × 5000 = 2100 psia = 2050 psia= 2100 psia = 2050 psia → → Pg = 0.08 D + 2100 → Pg = 0.08 D + 2050Pg = 0.08 D + 2100 → Pg = 0.08 D + 2050 Water pressure Pω = 0.45 D + 15 Water pressure Pω = 0.45 D + 15Water pressure Pω = 0.45 D + 15 Water pressure Pω = 0.45 D + 15 At GWC Pg = Pω At GWC Pg = PωAt GWC Pg = Pω At GWC Pg = Pω 0.08 D + 2100 = 0.45 D + 15 0.08 D + 2050 = 0.45 D + 150.08 D + 2100 = 0.45 D + 15 0.08 D + 2050 = 0.45 D + 15 D = 5635 ft (GWC) D = 5500 ft (GWC)D = 5635 ft (GWC) D = 5500 ft (GWC)

Results from Errors in GWC or GOC or Results from Errors in GWC or GOC or OWC OWC

GWC or GOC or OWC location GWC or GOC or OWC location

affecting affecting

volume of hydrocarbon OOIPvolume of hydrocarbon OOIP

affectingaffecting

OOIP or OGIPOOIP or OGIP

affectingaffecting

development plansdevelopment plans

2.4 Reservoir 2.4 Reservoir TemperatureTemperature

Reservoir temperature may be expected to coReservoir temperature may be expected to conform to the regional or local geothermal gradnform to the regional or local geothermal gradient.ient.

In many petroliferous basins this is around 0.02In many petroliferous basins this is around 0.029 k/m (1.69 k/m (1.6ooF/100 ft).F/100 ft).

The overburden and reservoir rock, which have The overburden and reservoir rock, which have large thermal capacities, together with large slarge thermal capacities, together with large surface area for heat transfer within the reservourface area for heat transfer within the reservoir, lead to a reasonable assumption that reservir, lead to a reasonable assumption that reservoir condition processes tend to be isothermal oir condition processes tend to be isothermal

119119

120120