Apply Rock Mechanics in

Reservoir Characterization

Msc Julio W. Poquioma

Chief Reservoir Engineer

PetroSA

Mobil: +27 79 492.02.52

Email julio.poquioma@petrosa.co.za

Aberdeen, April 18 – 20 / 2012

Content

Introduction

Theory

Tools

Application

Conclusion

Introduction

Geomechanics is an Engineering discipline that study the

mechanical behaviour of the geological materials (rock

and soil) under extremes changes (stress, strain,

temperature, chemical).

Rock Mechanics in Field Development

Reservoir Characterization Process

GEOPHYSIC STUDY

•Horizonts Correlations

•Fault Maps

•Seismic Stratigraphy

•Isopac Maps

•Seismic Attributes

•Seismic Inversion

•Facies Map, Porosity

GEOLOGICAL STUDY

•Stratigraphycs Correlations

•Core Descriptions

•Sedimentology

•Facies Interpretation

•Structural Analysis

•Petropysical Analysis

•Diagenisis

•Geometry/Pore Type

GEOMECHANIC STUDY

•Tests: Mechanics Strengh, Stress

Direction and Magnitud,

•Inyectivity Test

•Breakouts, Ovalizations

•Digital Sonic

•Wells Operation Evaluation

•Natural Fracture Orientation

PETROPHYSICAL STUDY

•Cut-offs determination

•Parameters : m, n, Qv

•Properties: Sw, K, ANP

•Fluid contacts

•Reservoir zonification

•Cross Plot

GEOLOGICAL MODEL

•Depositional Distribution

•Facies Distributions

•Petrophysical Prop. Distribution

•Structural Configuration

•Geological History

•Flow Units

•Barriers

GEOMECHANICAL MODEL

Areal Distribution on:

•Stress Magnitud

•Stress Direction

•Rock Mechanic Strength

•Rock Modulus

•Natural Fracture

RESERVOIR ENG. STUDIES

•Well Testing Analisis (WTA)

•Production by Flow Unit

•Decline Curves

•PVT Analysis

•Drive Mechanism

•Special Core Analysis (SCAL)

•Production Logs (PLT)

•Productivity Index (PI)

•Material Balance

•Reserves Calculations

•Development Potential

GEOSTATISTIC ANALYSIS

•Reservoir Properties Maps

•Facies Map

•Well Tendency Distribution

•Geostatistical Modeling

•Equiprobable Geological Models

RESERVOIR MODEL

•Grid Building

•Rock and Fluid Properties

•Flow Units Zonification

•Units Geometries

•Barriers and Acuifers

NUMERICAL SIMULATION

•Initialization

•History Match

•Petropysical Properties Dist.

•Facies with Petropysical

Properties

•Structural Configuration

•Geological History

•Flow Units

•Barriers

EXPLOTATION STRATEGY

ECONOMICAL EVALUATION

•Production Forecast

•Value Forecast

•Regulation and Costs

•Distribución Propofisicas

•Market Behaviour

•Sensibilities

DEVELOPMENT PLAN

•Well Drilling

•Infrastructure

•Well Stimulation

•Workovers

•Enhanced Oil Recovery

EXECUTION STRATEGIC

•Workflow and Plan

•Costs

•Risks

Geological Stress State

• There are three

stresses originally in

equilibrium:

• Sv or vertical stress,

• SH or maximum

horizontal stress and,

• Sh or minimum

(least) horizontal

stress.

Mechanical Shear Resistance

t : Shear resistance.

co : Cohesive resistance.

f : Internal friction angle.

Principal Stresses Direction

From Core Analysis

ASR DSA

New Technology Old Technology

Principal Stresses Direction

From Log Analysis

Six Arms Caliper Image Logs

Principal Stresses Magnitude

Vertical Stress (Overburden)

From Density logs From Correlation

Principal Stresses MagnitudeMinimum and Maximum Horizontal Stresses

From Injectivity Test (Microfrac / Minifrac or XLOT)

Rock Mechanics Tools

Laboratory Test

Field Test

Geological Core Analysis

Petrophysical Logs

Well Model

Numerical Reservoir Simulation Coupled

with Geomechanics

Theoretical Analysis

Stress State

Rock Properties

Analytical Solutions

– Elasticity and Poroelasticity

– Plasticity and Poroplasticity

Numerical Solutions

– Finite Differential Method

– Finite Elements Method

Modelling and Simulation

Well Modelling.

Structural Geological,

Modelling Stress, Strain,

Temperature and Flow.

Numerical Reservoir

Simulation, Coupled with

Rock Mechanics.

Application of Rock Mechanics

Structural Geology

Wellbore Stability

Hydraulic Fracturing

Sand Production

Naturally Fractured Reservoirs

Unconsolidated Sand Reservoirs

Tight Sand and Shale Gas

Wellbore Stability

Mud Window

FpShPp

Pore Pressure Minimum

Horizontal StressFracture

Pressure

Mw

Minimum

Mud Weight

Hydraulic Fracturing

Sand Production

Mechanical Resistance vs Destabilizing

Stresses.

Mechanical Resistance Depends on Rock

Properties and Stresses State Around It.

Destabilizing Stresses Depends on Stress,

Pressure Drawdown and Drag Forces

Inherent to the Fluid.

Sand Production

A reduction of Pwf causes an increase in

the tangential stress and a reduction in the

radial stress. Thus, increase the shear

stress.

The increase of drawdown causes an

increase in the shear stress, until achieve

the limit of the shear resistance.

Perforation Stability in Consolidated Sand

Erosion in Surface Tools Due Sanding

From Sand Management Forum, 2004.

Separator Full of Sand

From Sand Management Forum, 2004.

Sand Control

Gravel Pack

Prepack Borehole screen

Optimum choke size according critical Pwf

(sonic / simulator) and production monitoring

Hydraulic fracturing

High inclined (slant) wells

Oriented perforation under balance

Gravel Pack

Conventional casing

High shoot density

Charges with big diameter,

bypassing the damaged zone

After perforation, cleaning and

crossover circulation

Very useful technique

Prepack Screens

Fracpack

More than 60% of offshore

wells in USA has been

completed fracpack

Tip screenout fractures

(short and wide fracs)

combined in a gravel pack

operation.

Bypassing damaged zone

Reduce the production of

fines due an optimum

drawdown and flow velocity

Perforation Phase and Density Model

Oriented Perforation Under Balance

Results, experience somewhere in Venezuela

Conclusions

Reduce uncertainties in the Reservoir

Characterization

Optimize Drilling Trajectory/Completion Activities

Optimize Perforations/Hydraulic Fracturing

Sand Control (Preventive / Corrective Methods)

Naturally Fracture Reservoirs

Subsidence and Compaction Strategic

Optimal Development Plan by Numerical

Reservoir Simulation Coupled with

Geomechanics