Data and Model Base of Customized Hydraulic Fracturing for Continental Shale Oil

Abstract

Abstract The challenges of lacustrine shale oil reservoirs include not only subsurface heterogeneity of reservoir quality and but also the effect of natural fractures on propagation of hydraulic fractures and associated fracture hits. The intercalated sandstone and shale in a gravity deposit setting result in significant variation in the reservoir quality. Meanwhile, the subsurface conditions become even more complicated when the reservoirs are naturally fractured. The objective of this study is to characterize reservoir quality, natural fractures, and completion quality with well, seismic, and fracturing data, eventually to provide a base for a customized fracturing job according to the local geology aiming to enhance reservoir recovery. A geological model and a geomechanical model were built integrating all available data, including logs, core data, and seismic data, and an ant-tracking algorithm was used with variance of the seismic data as the input to delineate natural fractures. The quality check was performed by comparing drilling data, microseismic data, and fracturing data. A distributed fracture network (DFN) model was built with the ant-tracking results. Fracture stability analysis was performed when the natural fracture model and geomechanical model were ready. The fracturing design was customized and optimized with the models mentioned above and understanding obtained from the analyses. Different fracturing strategies were applied to each stage and to each well of the same pad based on the geoscience models. Some wells were completed with large-volume and high-rate fracturing practice to maintain the long-term reservoir pressure. Alternatively, some wells were subject to an intensive staging with low-volume and low-rate fracturing practice to create better near-wellbore flowing conditions. The combination of customized fracturing design and real-time adjustments during execution was approved to be a valid and practical geoengineering approach. The benefit of the workflow includes not only high fracturing efficiency, but also the effects on production performance. Production data measured by multiphase flow metering showed that the customized approach results in a 20% production increase.