The Changqing field consists of many individual oil fields that stretch across a large area in the Ordos Basin of north central China. Oil reservoirs in the Changqing field typically consist of stacked sand/shale deposits with the majority of the target zones having low permeabilities of 0.05 to 0.3 md. All oil wells completed in these tight reservoirs are fracture stimulated to achieve commercial production. Fracture stimulation is also commonly done in injection wells to enhance injectivity in reservoirs under waterflooding. In a successful water injection program, it is critical to achieve optimal fracture parameters (fracture length, azimuth, and conductivity) for both the injection and production wells. Improper well placement and fracture design can lead to high injection pressures, early water breakthrough, and overall low oil recovery.
This paper presents the results of two case studies to evaluate hydraulically fractured well performance of two oil reservoirs in the Changqing field. Microseismic fracture mapping was used to determine fracture geometry and azimuth. Fracture modeling was used to determine effective fracture length, height, and conductivity. The microseismic mapping and fracture modeling results were integrated into a multi-layer, multi-phase and multi-well reservoir simulator to determine the effectiveness of fracture geometry, conductivity and well placement on water injectivity and oil recovery for inverse 5-spot and rectangular drive water injection schemes.
Author(s): E.P. Lolon; StrataGen Engineering, PetroChina Changqing Oilfield Co., C.L. Cipolla; StrataGen Engineering, Xinghui Liu; Pinnacle, Xianwen Li and Baochun Chen, and Chengwang Wang
Paper Number: SPE 121528