Optimization design of hydraulic fracturing parameters for dense perforations of the high-angle deviated well in shale oil reservoirs

Abstract

Onshore shale oil reservoirs in China possess unique characteristics such as large thickness, thin individual layers, significant interbedded sweet spots, and numerous stress barrier layers. Traditional hydraulic fracturing technology for horizontal wells has limited effectiveness in traversing layers longitudinally. To address this issue, we propose utilizing highly deviated wells for the fracturing design and development of onshore shale oil. Based on the integrated concept of geological engineering, a coupled modeling approach is employed to integrate multi-layered stacked shale oil reservoirs, natural fractures, and geomechanics. Subsequently, numerical simulations integrating fracture initiation, propagation, and fluid flow are conducted for highly deviated well fracturing. A sensitivity analysis is then carried out to identify the primary controlling factors influencing fracturing effectiveness. In accordance with the geological characteristics of the working area, numerical simulation results indicate that segmented volume fracturing with a cluster spacing of 12 m achieves favorable reservoir modification effects in multi-layered stacked shale oil reservoirs. When the construction fluid volume ranges from 1.3 × 103 to 1.5 × 103 m3 per segment, the pumping rate is 7 m3/min, and the sand addition intensity is 2.5 m3/m, favorable fracture modification volume and post-fracturing yield are observed. Finally, post-fracturing effects are evaluated using microseismic and on-site production data, revealing a positive correlation between single-well fluid injection volume and sand addition quantity with microseismic detection effectiveness, thus validating the reliability of the numerical simulation for fracturing design. Through rational design of segmented fracturing in highly deviated wells and a targeted "low sand ratio, gradual increase combination pumping process optimization" strategy for sand addition, sand plugging phenomena are not observed during on-site highly deviated well fracturing, achieving safe sand addition. The research findings provide important guidance for the design and parameter optimization of hydraulic fracturing in high-displacement wells in onshore shale oil reservoirs.

Keywords

• oilfield development
• reservoir stimulation
• highly deviated wells
• shale oil
• stacked formation
• geology-engineering integration
• numerical simulation