Dynamic analysis of fractured horizontal wells in shale reservoirs considering lithological differences of bedding fractures

In view of the development of bedding fractures in near-horizontal direction of shale reservoirs and a large difference in lithology on both sides of the bedding fractures, in this study, a fractured horizontal well model was established in shale reservoirs considering both bedding fractures and microfractures, in which the bedding fractures are flanked by unstable channeling of shale and mudstone matrix, and organic matter adsorption and inorganic matter slip effects were considered in the shale matrix. The pressure of the fractured horizontal well with constant production rate was obtained based on the Laplace transform and superposition principle, and compared with the classical Kazemi unsteady fracture flow model to verify the correctness of the new model. The influencing factors of pressure and production rate of the fractured horizontal well were analyzed. The results show that the flow in the fractured horizontal well can be classified with seven stages, including well-bore storage, artificial fracture bilinear flow, bedding fracture unstable flow, microfracture quasi-stable flow, formation linear flow, channeling of shale and mudstone to bedding fracture, and formation radial flow. The bedding fractures have a significant effect on well pressure and production in the early stage, and the greater the inflow capacity, the smoother the pressure derivative, the higher the production rate. Shale and mudstone channeling mainly manifested after formation linear flow, and the pressure and production rate change with the relative size of shale and mudstone matrix channeling capacity and elastic storage capacity ratio, indicating the influence of the lithological differences between the two sides of the bedding fractures on production dynamics, the larger the differences the earlier the channeling time and the lower the production. © 2024 University of Petroleum, China. All rights reserved.