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Lateral reservoir heterogeneities and their impacts on stress shadowing in the Eagle Ford reservoir
Alrashed, Ahmed Ali
Alrashed, Ahmed Ali
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2018
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Optimizing hydraulic fracture spacing in horizontal wells of unconventional reservoirs requires investigating the extent of stress shadowing and the influence of rock quality lateral variations. For that purpose, a base hydraulic fracture model was created for a well in the Eagle Ford reservoir. Fiber optic distributed acoustic sensing (DAS) data analysis was utilized to find the individual perforation cluster contribution based on the total proppant placed in each cluster. The modeled well cluster contribution and production data were matched with actual data. Reservoir and geomechanical properties for certain fracturing stages of the horizontal wellbore were altered from the base model to address the effect of rock quality lateral variations. The sensitized properties include matrix permeability, Poisson’s ratio, Young’s modulus, and Biot’s coefficient. In response to these changes, the new flowing fracture lengths of the four simulated stages were calculated and compared to the base model values. It was found that fracturing stages with a higher matrix permeability of 0.0023 mD, compared to a base case value of 0.00023 mD, were able to create fractures with larger flowing fracture length by 69%, 68%, and 48% in the heel, middle, and toe clusters, respectively. Increasing Poisson’s ratio from 0.28 to 0.33 caused changes in the flowing fracture lengths by 32%, 41%, and -1.4% in the heel, middle, and toe clusters, respectively. Compared to a Young’s modulus base case value of 5.5 MMpsi, a 6.5 MMpsi value resulted in decreasing the flowing fracture lengths at rates of -8%, -3%, and -24% in the heel, middle, and toe clusters, respectively. Decreasing Biot’s coefficient from 0.9 to 0.1 reduced the flowing fracture lengths in the heel, middle, and toe clusters at rates of -44%, -32%, and -39%, respectively. Overall, the rate of increase in flowing fracture length at the performed sensitivity analyses was more pronounced in the heel and middle clusters and less evident in the toe clusters. Four scenarios of 57’ (Scenario 1), 76’ (Scenario 2), 100’ (Scenario 3), and 142’ (Scenario 4) spacing between perforation clusters were run to address the effects of stress shadowing. Simulations showed that the tightest spacing scenario (Scenario 1) yielded the largest fracture network volume due to the higher number of clusters. However, these created fractures were less conductive than the ones created with wider spacing scenarios. Scenario 1 average cluster contributions based on fracture conductivity were 56%, 29%, and 15% for the heel, middle, and toe clusters, respectively, compared to more uniform contributions of 36%, 28%, and 36% for the heel, middle, and toe clusters, respectively, in Scenario 4. In terms of production, Scenario 1 forecasted the highest cumulative oil production of 355,000 STB in 30 years compared to 256,000 STB production of Scenario 4. Therefore, the created fracture network volume, which is an indication of reservoir contact, was more influential on production than fracture conductivity for the studied case.
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