Apply Rock Mechanics in
Reservoir Characterization
Msc Julio W. Poquioma
Chief Reservoir Engineer
PetroSA
Mobil: +27 79 492.02.52
Email [email protected]
Aberdeen, April 18 – 20 / 2012
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).
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 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
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.
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
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
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
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