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Discover a Career

By definition, rock mechanics is the

theoretical and applied science of

the mechanical behavior of rocks

in the force fields of their physical

environment. In practice, so-called

“rock engineering” is concerned

with the application of principles of

engineering mechanics to the design

and construction of structures of any

type either on or in the rock, such as

tunnels, mine shafts, underground

excavations, open pit mines, road cuts,

dams, skyscrapers, waste repositories,

and oil or gas wells.

Though initially developed

for mining and civil engineering

 purposes, geomechanics found its

way into the oil and gas industry in

the ’80s in order to improve hydraulic

fracturing and drilling operations.

In the contemporary petroleum

industry, geomechanics is defined

as the discipline that integrates rock

mechanics, geophysics, petrophysics,

and geology to quantify the response

of the Earth to any changes in

state of stress, pore pressure, and

formation temperature.

Geomechanics: The Oil and

Gas Industry’s Missing Link

 Al though systematic application of rock

mechanics in the oil and gas industry

is relatively new, it was recognized and

appreciated by many oil companies

in a short period of time and has

become a fast-growing field due to

its applicability and effectiveness in

reducing nonproductive time (NPT).

 As the virgin state of stress is

disturbed by different oil and gas

activities, the rock’s mechanical

state changes, too, and consequently

influences dr illing, completions,

and production performance. These

changes can result in serious and

unexpected cost and time overruns if

not properly predicted and managed.

Dodson et al. (Offshore , Vol. 64, No. 1,

2004) conducted a survey of Gulf of

Mexico wells and reported wellbore

stability issues were the cause of almost

40% of dri lling-related NPT, resulting in

an annual cost of around USD 8 billion.

 As a result of experiencing

significant improvements in drilling

and production operations by utilizing

geomechanics, it has hence become

an important and i ntegral part of each

and every field development plan,

from the early stages of exploration

to even after field abandonment. With

the recent boom in the development of

unconventional oil and gas resources,

the use of geomechanics principles

has become even more imperative

due to the sensitivity and complexity

of these reservoirs. Geomechanics is

 playing a crit ical role in successfu lly

maximizing shale gas production by

helping optimize the use of hydraulic

fracturing technology.

Geomechanical applications in

the oil and gas industry include pore-

 pressure prediction; helpi ng ensure

cap-rock integrity; field problem

diagnosis; formation properties

evaluation; in-situ stresses estimation;

drilling performance evaluation;

wellbore stability; borehole trajectory

optimization; sand production

 predict ion and control; underbalanced

drilling feasibility; fractured reservoir

characterization; and production

maximization affected by natural

fractures, hydraulic fracturing, fluid and

steam injection, reservoir compaction,

surface subsidence, and casing shear

and collapse. It’s a long list!

Clear knowledge of how to apply

geomechanics appropriately will

increase exploration and development

efficiency in both conventional and

unconventional resources.

Geomechanical Modeling:

Turning Impossibilities

Into Possibilities

To conduct any of the a forementioned

studies using rock mechanics, the first

step is to construct a geomechanical

Earth model (GEM). A GEM consists

of six core components that need to be

either calculated or estimated using

field data:

Discover a Career in GeomechanicsHamed Soroush, Shell International Exploration and Production

Hamed Soroush is an internationally recognized geomechanics expert with

more than 17 years of experience applying principles of rock mechanics within

the mining, civil, and oil and gas industries. He has conducted or managed more

than 100 consulting and research projects worldwide and is currently working

for Shell as a geomechanics advisor in Houston. Before that, Soroush was the

global geomechanics advisor for Weatherford, based in Dubai, providing project

coordination, support, and training for geomechanics and petroleum engineering

applications. He has also worked with numerous other companies in the Middle

East, Asia Pacific, North Sea, and South America regions. Soroush holds a BSc in

mining engineering, an MSc in rock mechanics, and a PhD in petroleum engineering

from Curtin University of Technology in Australia. He has published three technical

books and many journal and conference papers. Soroush has given several

industry short courses and has served as a steering committee member for many

conferences and workshops. He was selected as an SPE Distinguished Lecturer

for 2012–13, presenting on the geomechanics of unconventional resources.

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Discover a Career

• Vertical stress, δv  (often referred to

as the overburden stress)

• Maximum horizontal stress, δH max

• Minimum horizontal stress, δH min

• Stress orientation, Azi δH max

• Pore pressure, P  p

• Rock mechanical properties

Modeling techniques in

geomechanics encompass analytical,

experimental, and numerical methods,

each having their pros and cons.

Generally, numerical models have

higher accuracy over analytical ones

but require additional input data and

more time. Analytical techniques are

in return quicker with less complexity.

Experimental models are based on

 physical and mechanical laboratory

tests on rock core samples. It is

usually costly and time consuming

to perform such tests, though they do

 provide valuable in format ion about

rock properties.

 As a generic workflow, constructi ng

a 1D geomechanical model starts with

rock mechanical property estimation

using petrophysical logs in conjunction

with core test results. There are

different empirical models to make a

strength profile; however, laboratory

data are required to calibrate

these models.

The second step is building a

continuous overburden profile using

density logs.

Pore-pressure prediction using

logs and available well test data (or

seismic data if available) is the next

step. Minimum horizontal stress can

be calculated using either empirical

equations or fracturing data (LOT

[leak-off tests]/X [extended] LOT

or minifracturing tests) or ideally, a

combination of both. Drilling incidentssuch as ballooning and mud losses

can help to constrain the minimum

horizontal stress and fracture gradient.

The last steps are determining

azimuth and magnitude of the

maximum horizontal stress. This

is the most complicated part of

geomechanical modeling, as no direct

way of measuring δH max is available.

 Analyzing wellbore fai lures such as

breakouts and drilling-induced tensile

fractures from image logs is one of the

existing techniques to determine a

reasonable range for δH max and find its

orientation. Using caliper logs, sonic

logs, and laboratory measurement

of elastic strain recovery are

alternative techniques.

Many field examples have proved

that geomechanical analyses can open

opportunities for drilling i nto harsh

and challenging environments which

 previously looked impossible. In an

example in southeast Asia, where

drill ing a vertical well was identified

as impossible due to lack of a safe

operating mud weight wi ndow, the well

was made possible by geomechanical

analysis that led to changing the well

trajectory to the safest orientation

in a specific formation and thereby

widening the window.

Geomechanics can also improve

casing design and provide a wider mud

weight window for drillers. There are

examples in Northwest Shelf Australia

where geomechanical modeling

reduced the number of casings,

resulting in signi ficant cost savings for

the operators.

In the context of production from

naturally fractured reservoirs, a

GEM can make a real difference in

maximizing production by identifying

critically stressed fractures which

are, in fact, the productive fractures.

Identifying the orientation of these

fractures enables optimization of

drilling orientation to intersect the

maximum number of them. Field

examples in the Middle East and

southeast Asia have shown notable

increases in production using these

types of studies.

Distinguish Your Career

With Geomechanics

Due to the remarkable contribution

geomechanics has made to the oil

and gas industry in solving a plethora

of problems related to exploration,

drilling, completion, intervention,

 production, and i nject ion operations,

geomechanics specialists can be

called petroleum engineering

troubleshooters. Considering all the

benefits geomechanics has brought to

the industry, there has been escalating

appreciation during the last decade

from operating companies toward

using it in their operations. Time

and money savings by big operators

through using geomechanics have

convinced them to either establish a

geomechanics capability in house or

ask for support from external experts.

This increasing demand has created

a huge potential job market for young

 professionals in terested in building a

career in geomechanics.

Current ly, however, the oil and

gas industry suffers from a lack of

enough competent resources in this

field; this is because universities offer

only a limited number of specialized

 programs in petroleum geomechanics.

 Although few un iversit ies offer rock

mechanics courses at the postgraduate

level, they are usually in mining or

civil engineering departments. As a

result, there is a lack of professionals

with academic backgrounds in rock

mechanics specifically related to

the oil and gas industry. It should be

noted that rock mechanics requires

a comprehensive understanding of

mathematics, physics, and mechanics,

and, therefore, having the appropriate

academic background is a critical

factor in pursuing a successful career

in geomechanics.

Generally speaking, people

with engineering backgrounds are

better candidates for becoming

geomechanics specialists. Indeed,

geomechanics can be as lethal as it

is useful if it is used by a person who

does not understand the mechanical

behavior and strength of materials.

Being a software user withoutunderstanding the theories and

concepts hidden behind the screen is

extremely dangerous and can result

in misleading outputs which may

 put a project in jeopardy. There are

many cases where companies have

lost faith in geomechanics due to

bogus results generated by so-called

“geomechanics specialists” who

lacked the appropriate background,

credentials, and experience.

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Thus, it is strongly recommended

for students with an interest in

geomechanics to take any and all

rock mechanics-related courses

during their engineering degree,

or, if completing a nonengineering

degree, learn the necessary

mathematics and mechanics.

Combining a relevant academic

background with some industry

experience can lead to an exceptional

career which can give you the

opportunity to choose whether you

want to work in the operating or

consulting sectors.

 A geomechan ics career is usually

associated with a lot of traveling all

over the world, which makes it very

attractive and exciting. Dealing

with a host of different geomechnics

applications in petroleum engineering

can prevent you from getting stuck in

a rut and keep you busy by providing

opportunities to learn new things and

face new challenges.

The nature of geomechanical

studies requires a highly focused

multidisciplinary team approach

and close interaction with other

experts. This provides opportunities

to learn about other interesting

disciplines, which is another attraction

of this field. For instance, when a

geomechanics specialist performs

an analysis for sand production

 prediction and management, he

or she must work closely with

completion engineers and production

technologists. This provides the

opportunity for improving one’s

knowledge about completion

technologies, production techniques,

and different sand control tools.

 Alt hough the job market in

geomechanics is not very competit ive

at the moment due to the scarcity of

high-quality experts, it is sti ll essential

for people in this field to improve their

knowledge and capabilities and update

themselves on state-of-the-art advances

and technologies in order to distinguish

themselves and to stay on top of their

career. Geomechanics specialists are

expected to fully understand related

industry problems and be able to

 provide i nnovative solutions using

their rock mechanics knowledge.

Good knowledge of mathematics and

 physics helps you to develop your own

analytical and numerical models and

have full command of what you are

expected to do.

Because geomechanics is a new

science, there are many avenues

open for research and development.

Therefore, creativity and having new

ideas are key to a successful and

evolving career. In addition to all

the attractions and challenges of a

geomechanics career, it remains one

of the exceptional multidisciplinary

fields that give you the facil ity to move

to other industries like civil and min ing

should you feel like making a big

change in your career. TWA