Modeling and field-testing of fracturing fluid back-flow after acid fracturing in unconventional reservoirs.

Abstract When the oil shale reservoir completes acid fracturing, the back-flow of fracturing fluid program is needed. In this paper, a three-dimensional model is established and the finite element analysis software is used to simulate the feasibility of gas lift back fracturing fluid in Fuyu oil shale formation after acid fracturing. The results show that when the injection pressure of FK-1 well is 8.5 MPa, the fracturing fluid can be effectively displaced. Fracturing fluid is discharged along the fracture into FK-2 well, and a few fracturing fluids overflow the pyrolysis zone along the direction of oil shale bedding. Then the experiment is carried out to verify the accuracy of numerical simulation. What's more, it is also verified that the connectivity of oil shale reservoir meets the needs of oil shale in-situ pyrolysis process. Graphical abstract Image 1 Highlights • Flow-solid coupling analysis simulated the back-flow fracturing fluid experiment. • Back-flow fracturing fluid by high pressure nitrogen displacement was carried out. • Pressure oscillation for formation connectivity test is proposed. [ABSTRACT FROM AUTHOR]