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Geomechanics: An effective multi-disciplinary

tool for natural integration of disciplines in

upstream Petroleum decisions.

SPWLA Kuwait Chapter – 26th March 2013

Satya Perumalla

GMI Geomechanics Services,

Baker Hughes.

Types & Challenges of Reservoirs

Geomechanics as a Tool: Multi-disciplinary interaction

Data gaps & implications

Ideal data situation & Benefits

Inter-dependency of disciplines

Acknowledgements.

Outline

Formation Challenges Scope for Optimization

3

Geomechanics for the Life of Well & Reservoir

SHmax

orientation

Reservoirs

Clastics

Carbonates

Fractured

formations

Tight/Shale Gas

Heavy Oil

CBM

Sour Gas.

Known Reservoir Problems

• Wellbore Stability in Formations above Reservoirs.

• Stress induced, Fractured Rock, Chemical, Loss circulation, etc.

• Clastics/Carbonate Conventional Reservoirs:

• No visible geomechanical impact on reservoir at early stage of

production.

• Depleted reservoir Injection/EOR changes the in-situ stress regime.

• Influence on field scale permeability tensor Scope for Optimization.

• Fractured Reservoirs:

• Location of fracture systems.

• Positioning Injection/Producer wells.

• Waterfront movement monitoring & Simulation/History matching.

Known Reservoir Problems

• Tight / Shale Gas Reservoirs:

• Hydraulic Fracturing

• Rapid production decline

• Stress sensitive sweep vs Well positioning.

• Heavy Oil:

• Influence of steam injection on reservoir & cap rock

• Integrity of cap rock and faults

• Sour Gas reservoirs:

• Well Integrity

• Zero tolerance for solids/sand production.

Behavior of Any Reservoir

• Mechanical Response of Reservoir Rock – Completion

– Production

– Injection

– EOR

• Where is the bottleneck in Life Cycle of Each Reservoir

Type?

Decision Support Questions

Stage Problem

Exploration How to identify sweet spots?

Pore pressure

Fault Trap evaluation

Development Drilling Wellbore Stability

Completion What type of completion can

maximize flow?

Can I have a hydraulic frac in

desired interval?

How best to benefit from natural

fractures

How to avoid any sand/solids

production

Decision Support Questions

Stage Problem

Production

Where is the scope for

Optimization?

Why reservoir simulation do not

make me happy?

Does conventional peripheral

injection is effective?

Seem to be missing something!!

Geology.com

Natural fracture patterns vary Breccia zone – Monterey Shale California

Marcellus Northeast U.S.

Paleozoic “fissile” shale Tulsa area

About.com

Interbedded Massive/laminated

Squidoo.com

Slickensides on fault surface

Event cloud shape and reservoir drainage area

Northeast US – two often well-

developed orthogonal joint sets

Larger stress anisotropy;

stresses sub-parallel to joints

Barnett – contains a significant

number of steeply dipping

conjugate and a wide range of

fractures strikes

Low horizontal stress

anisotropy

SPE 2007

Cotton Valley – one strong, well-

developed, near-vertical

fracture set +/- parallels SHmax

Moderate stress anisotropy

Rutledge

Fracture Permeability Results

-

GMI•MohrFracs™ results for Amin Formation

Effective normal stress [ppg]

Sh

ear

str

ess [

pp

g]

Coulomb failure Function [ppg]

Not critically stressed

Critically stressed

Perumalla et al 2011

Natural fractures

identified in well

),( closure

noafAperture

Effective normal stress

Rela

tive p

erm

eabili

ty

Stress – Aperture Coupling

© 2012 Baker Hughes Incorporated. All Rights Reserved 13

n – effective normal stress

ao – fracture aperture at n = 0

after Hossain et al., 2002; Tezuka et al. 2005, Moos and Barton, 2008

Variation in aperture as a function of normal stress:

closure

n

closure

n

14

Start of shear slip of significant population of natural fractures

Stimulation of Natural Fractures

Geomechanical Discrete Fracture Network

Model

• Identifying potential fracture corridors that are easy to

stimulate.

Concentration index of critically stressed fractures (iCSF)

Fault Leakage

A-Central

Fault

Small increase in pore

pressure will cause fault to

slip

gas leakage area

16

© 2012 Baker Hughes Incorporated. All Rights Reserved.

Hydraulic Fracture Propagation

Pay

Pay

“Perfect”

fracture

Multiple fractures

dipping from vertical

T-shaped

fractures

Twisting

fractures

Out-of-

zone

growth

Poor fluid

diversion

Upward

fracture

growth

Horizontal

fractures

?

?

?

? ?

?

?

Pinnacle Tech. Ltd.

17

© 2012 Baker Hughes Incorporated. All Rights Reserved.

Relating Stage Contributions and Natural Fractures to Production: Impact on Field Development Plan

© 2010 Baker Hughes Incorporated. All Rights Reserved.

Rates measured by PLT 5 months later

7 6 5 4 3 2 1 8 9

30

25

20

15

10

5

0

B-values - 0.98 - 1.01 - 1.92 2.27 1.92 -

1 3 2 4 7 5 6 8 9

Natural

fractures

Events

Finite Element Methods to Study Rock

Behavior

19

Global Model 1st Sub-Model 2nd Sub-Model

3D Dynamic Geomechanical Model: Overview

Geomechanical Data Sources

21 ©

201

2

Bak

er

Hug

hes

Inco

rpor

ated

. All

Righ

ts

Res

erve

d.

Vertical Stress

Pore Pressure

Least Principal Stress

SHmax Magnitude SHmax Orientation

Rock Strength

Integrated density Density from acoustic/seismic

Direct measurements Log-based (acoustic, resistivity) Seismic (ITT, velocity cubes)

XLOT, LOT, minifrac, lost circulation, ballooning

SV

Shmin

PP

Analysis of wellbore failure Crossed dipole (orientation) “Active” geological structures

Core tests, logs, cuttings, analysis of wellbore failure

22

Data Gaps: Present Industry Standard

• Despite having Millions $$ budgets, Industry often misses

key data set necessary for the health of reservoir.

• Uncertainty in models can lead to decisions worth billions $$.

• Most trouble making formation during drilling often have no

data leads to ‘trial and error’ type optimization: less

effective.

• Cost for Data acquisition is extremely small when compared

to benefits from reservoir.

• Most of the times, lack of interdisciplinary understanding is

responsible for data gaps.

Ideal Data Situation

Trouble Data Use

Nasty Shales causing

wellbore instability.

Chemical, Osmotic core

properties.

Spectral Component logs

to calibrate.

Help drillers to overcome

wellbore instability.

Uncertainty with

Overburden stress

Run density/sonic log in at

least one well per field

Reduces model

uncertainty and

strengthens confidence.

Sand production after

depletion/Injection

Rock mechanical Tests Optimize drawdown

pressures and depletion

strategy.

Influence of stress on

sweep efficiency is

unknown

MicroFrac/MiniFrac/XLOT

at different corners of

reservoir at different

depletion stages.

Improved predictability in

fluid movement, EOR,

Injection planning.

24

Inter dependency of disciplines

• Often, most needed data for one discipline is obtained by

other discipline.

• Drillers need shale and shallow formation properties to

overcome wellbore stability, but Sub-surface

professionals usually don’t characterize those formations.

• Sub-surface Professionals need

XLOT/MicroFrac/MiniFrac, but Drillers show less

encouragement to acquire these data.

Loss of opportunity for both disciplines.

• Similarly, inter-dependency among Production Engg,

Production Technology, Petrophysicists, G&G on integrated

data acquisition is the key for success of overall reservoir

performance.

Thanks to You all!

SPWLA – Kuwait.

Baker Hughes.

Acknowledgements