Geological Engineering Integrated Fracturing Technology for Qingcheng Interlayer Shale Oil

Qingcheng interlayer shale oil possesses the characteristics of tight reservoirs, a low pressure coefficient in the original reservoirs, and significant heterogeneity in lacustrine sediment. According to the methods of large-scale physical model experiment, coring observation of horizontal inspection wells, and microseismic frequency and magnitude analysis, the fracture morphology of the fracture system was mainly artificial main fracture, followed by branch/microfractures. The idea of subdividing and cutting fractures was applied, and the segmented multi-cluster perforation joint cropping process using bridge plug/ball block was taken as the main technology. Starting from the comprehensive sweet spot characteristics of geological engineering, the fracture layout strategy, segment and cluster combinations, and cluster spacing were optimized. Based on the principle of limited entry fracturing, the multi-cluster fracture propagation was controlled by temporary plugging, and the key parameters of fracturing were optimized with a large number of on-site fracturing data as the sample set. According to the demands for fracture network flow conductivity, the particle size combination of fracturing fluid and proppant was optimized, and the development of a geological engineering integrated fracturing technology specific to Qingcheng interlayer shale oil was formed. The 180 horizontal wells in Qingcheng shale oil block were fractured in 4 590 stages using the geological engineering integrated fracturing technology. After fracturing, the initial production of a single well reached 14.5 t/d, and the production decline rate in the first year was reduced by more than 10 percentage points. The research and field applications have demonstrated that the the geological engineering integrated fracturing technology for shale oil can effectively match oil reservoirs and fractures, thereby providing vital support for achieving a million-ton production capacity in Qingcheng shale oil. This technology also contributes to the efficient utilization and beneficial development of continental shale oil resources.