Applications of Geomechanics | What is the use of geomechanics?
Assignment Applications of Geomechanics
You’ve been asked by your manager to:
- Describe the steps involved with a coupled geomechanics model.
- Explain the changes in the reservoir production over time using a Mohr’s circle that includes:
- Where initial stress plots on the Mohr’s circle
- Where the stress plots after injection
- Where the stress plots after depletion
- Where shear failure occurs
- Where compaction is activated
- In the shale reservoir your team is currently working on, the geomechanical model predicts that the natural fractures will be displaced when under pressure. Why is this happening and is it to your advantage?
Solution
1. Geomechanics modeling begins by constructing a 3D geomechanical model of the reservoir, the surrounding formations and one or more wells. Each geocell in the model is populated with rock mechanical parameters. Geocells in the reservoir also contain the reservoir parameters. The model contains the input parameters required by a geomechanics simulator and a reservoir simulator. An iteratively coupled geomechanics-reservoir simulation proceeds as follows (Figure 1):
Step 1: The geomechanics simulator computes the equilibrated state of stress and strain given the boundary conditions, initial pore pressure and the initial rock properties.
Step 2: The reservoir simulator computes a change in reservoir pressure caused by an increment of production.
Step 3: The changes in reservoir pressure are exported to the geomechanics simulator.
Step 4: The geomechanics simulator then recalculates the stress and strain fields given the new reservoir pressure. Changes of stress and strain cause changes of porosity and permeability and these are exported to reservoir simulator.
Step 5: Pass changes in porosity and permeability to the reservoir simulator.This process is repeated from Step 2, until the production schedule has been fully simulated. The resulting calculations reveal the time evolution of pressure and rock deformation over the entire 3D volume, not just in the reservoir.
2.
3. When reservoir pressure increases due to injection, effective normal stresses will decrease and the Mohr’s circle will shift to the left. When that pressure reaches the shear failure point then displacement will occur along the fracture plane. An advantage would be that when displacement occurs, the naturally-fractured shale reservoir is likely to be stimulated by hydraulic fracturing thereby increasing permeability for production.
Assessment Applications of Geomechanics
1. Wells that are misaligned with the principal stress will have what type of result? (Select all that apply.)
A .Low breakdown pressures
B .Unfavorable reservoir stimulation
C .Favorable reservoir recovery
D .High breakdown pressures
E .Tortuous fractures near the wellbore
2. What type of reservoir are frac-packs typically used in?
A .Compacted, low porosity reservoirs
B .Weak, high porosity reservoirs
C .Weak, low porosity reservoirs
D .Compacted, high porosity reservoirs
3. Fractures propagate ___________ to Sh because it is the path of least resistance.
4. Completion applications are localized to the ___________ .
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