Fracture Propagation and Evaluation of Dual Wells Split-Time and Multi-Fracturing in Fuyu Oil Shale

Abstract

Reservoir stimulation is crucial for in situ exploitation as it directly impacts the efficiency of heat injection and transportation of oil and gas. In this study, dual wells split-time and multi-fracturing technology was designed, and a reservoir-scale hydraulic fracturing field experiment was conducted based on micro-seismic monitoring to figure out the fracture propagation. Furthermore, we extended the connection of micro-seismic events added with intensity based on Hugot’s research and innovatively proposed the step index and the path intensity to interpret the effect on hydraulic fracturing. The results showed that a three-dimensional fracturing zone with a length, width and height of 60×30×8m was generated at a depth of 476m to 484m, which lived up to a precise hydraulic fracturing as designed. Higher pump pressure and rate had a negative effect on hydraulic fracturing, which blocked the proppant migration according to the Poiseuille's law, depicting that the coefficient of viscosity of FK1-4 reached to 70 N·s/m2, and was 1.4 times as much as that of FK1-2 and FK1-5. The effect of hydraulic fracturing in FK1-4 was much better than that of FK1-2 and FK1-5, respectively. This study serves as a reference for follow-up oil shale exploitation via in situ pyrolysis.

Keywords: Oil shale, Hydraulic fracturing, Micro-seismic event, Fracture evaluation