Direct Measurements of Minimum Horizontal Stress, Permeability, and Permeability Anisotropy in a Siberian Oil Field Using a Wireline Formation Tester
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AbstractWaterflood management requires the optimization of hydraulic fracture placement. The lack of direct stress measurements (vertical distribution and direction) in the South Priobskoe field in western Siberia has created the need to determine the orientation and magnitude of the least principal stress. The presence of impermeable shales between producing sands complicates fracturing design and field development to maximize recovery. Permeability and permeability anisotropy at different depths are unknown variables that affect well completion and reservoir management decisions.A set of wireline formation evaluation tools were used for microfracturing (stress tests) at several sand and shale formations. The stress tests were performed by isolating 1 m of formation using the dual packer module of the wireline formation tester (WFT) and creating a hydraulic fracture by injecting drilling fluid using the downhole pump. Combination of the wireline dual packer and standard probe modules provided estimates of permeability and permeability anisotropy in sands. Formation microimagery data were used before and after stress tests to obtain information on least-principal-stress direction.Challenges created by the harsh working environments in western Siberia were addressed by detailed risk assessment, job planning, and real-time quality control and decision-making.The use of the acquired stress and permeability data to optimize the number of wells, well patterns, selection of water injectors, and fracture design is discussed.
