A Saturated Offshore Oil Reservoir We Have A Gas Cap Was Producing For More Than 15 Years And Its Pressure Has Reduced 1 (79.72 KiB) Viewed 26 times
A Saturated Offshore Oil Reservoir We Have A Gas Cap Was Producing For More Than 15 Years And Its Pressure Has Reduced 2 (69.09 KiB) Viewed 26 times
A Saturated Offshore Oil Reservoir We Have A Gas Cap Was Producing For More Than 15 Years And Its Pressure Has Reduced 3 (59.34 KiB) Viewed 26 times
A saturated offshore oil reservoir (we have a gas cap) was producing for more than 15 years and its pressure has reduced to 1000psi (top of gas cap). The initial reservoir pressure was 5000 psi. Some studies show that if reservoir pressure increases, the economic production rate will be achieved. However, there is an inactive cohesion-legs fault crossing the reservoir, and the reservoir engineer team is concerned about fault reactivation. The seabed is at 2000m depth and the imconformity depth is 2650m from the sea surface. (Below figure not drawn to scale) Below are the general data for the region . . • Average rock bulk density is different across the layer. The main reservoir has a density of 2.63g/cc Reservoir gas gradient 0.10 psi At • Reservoir oil gradient 0.35psi ft Reservoir water gradient 0.46 psi ft • Reservoir porosity: 20% Reverse stress regime (Shmin - 1.2 * Sv) . All Rocks: . Young's modulus: 40 GPa Poisson's ratio: 0.3 • UCS: 100 MPa Internal friction angle: 329 Tensile Strength: 9.8 MPa Fault friction coefficient: 0.52
Tensile Strength: 9.8 MPa Fault friction coefficient: 0.52 Assuming GOC (gas-oil contact) and OWC (oil-water contact) will not be shifted if reservoir pressure mcreases. a) What is the maximum regervoir pressure (top gas cap) which triggers fault reactivation? b) Do you expect any subsidence in the reservoir if pore pressure changes for 1000 psi? if yes, how many millimeters of change in the thickness of the reservoir is expected? c) At which pore pressure we will have rock failure? d) What types of failure is this? e) What are the normal (effective) and shear stresses at failure? f) What is the maximum shear strength of the fault? • What will happen if reservoir pressure reaches its initial value? Hint: You need to do the calculations for the most critical point among P, Q, and R (3 Marks out of 30). If you cannot identify the point, choose one and continue.
Saabad ter om Undenfoemes Denny:22 Umestone Density:271gles Shale Shale Density 604 Su water Reservoir Density: 2.63 SO Figure not to scale 501
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