Study on the influence of lamination density and perforation position on fracture height propagation and proppant distribution

Abstract

In the Bonan block of the Jiyang Depression, the lacustrine shale exhibits various types of organic-rich laminar lithofacies with complex distributions in lamination density and thickness, showing clear cyclic variations vertically over scales of several meters or even centimeters. These variations in lamination density and depth significantly impact the effectiveness of fracturing treatments in well placement. This study utilized downhole cores from the Shahejie Formation in the Bonan block, and based on the development characteristics of the lamination, a sampling scheme was designed. Small-scale true triaxial hydraulic fracturing experiments were conducted in the laboratory, focusing on the relationship between lamination density and perforation locations. Post-experiment analyses using computed tomography and acoustic emission monitoring examined fracture morphology, width variations, and proppant migration and placement within the fractures. The results indicate that high lamination density influences the propagation path of hydraulic fractures, restricting their vertical penetration through layers. Fracture initiation points closer to the lamination result in lower fluid injection pressure rise rates, thereby reducing the efficiency of the fracturing fluid. Lamination activated at the same depth generally produces narrower fractures than the main hydraulic fractures. Proppants are predominantly distributed within the main hydraulic fractures, with limited vertical migration into the lamination, resulting in the propped volume accounting for less than 10% of the total fracture volume. This study provides new insights and optimization strategies for well placement and perforation positioning in the hydraulic fracturing of organic-rich laminar lithofacies shale reservoirs.