Numerical study on the in-situ pyrolysis process of steeply dipping oil shale deposits by injecting superheated water steam: A case study on Jimsar oil shale in Xinjiang, China

Taking the oil shale deposits in the Jimsar area of Xinjiang, China as an example, this paper proposes an in-situ pyrolysis method using superheated steam suitable for steeply dipping oil shale. This method involves drilling parallel to the bedding and fracturing fractures perpendicular to bedding direction. High-temperature fluid is injected from the injection well to develop a larger heat exchange area through fracturing fractures and oil shale deposits. In this study, a thermal-hydraulic-mechanical coupling mathematical model considering oil shale anisotropy was established to study the in-situ conversion process. The results show that the new proposed method (hydraulic fracture number = 3) has the same heating efficiency as the traditional well layout method (drilling well perpendicular to beddings, fracture number = 3), but has the advantage of preventing shear damage to the wellbore and reducing the drilling cost; For the optimization of hydraulic fracture number and length, when the hydraulic fracture number is increased to 4 (fracture spacing = 20 m), the heating efficiency no longer significantly increases. When the fracture length increased, the heating efficiency does not significantly change. The results of this paper can serve as a reference for the study of in-situ pyrolysis of steeply dipping oil shale deposits. (c) 2021 Elsevier Ltd. All rights reserved.