Optimizing Refracturing Models in Tight Oil Reservoirs: An Integrated Workflow of Geology and Engineering Based on Four-Dimensional Dynamic Stress Field

Abstract

Abstract Integrated modelling of refracturing is a comprehensive and complex task for engineers involved in field development, especially in previously developed mature fields. The modelling process requires consideration of numerous factors to accurately predict fracture propagation patterns during refracturing and production. During the initial fracturing process, hydraulic fractures generate an altered induced stress field. Later, during the post-fracturing production process, hydrocarbon extraction causes formation pore pressure depletion, leading to further alterations in the stress field. However, due to the complexity of these phenomena, most existing workflows simplify the coupled simulation problems of stresses at different stages in the modeling process. Consequently, this often results in questionable hydraulic fracture geometries during refracturing and suboptimal refracturing designs. The goal of this study is to develop a novel integrated workflow for refracturing, specifically tailored for complex fracture networks. This model incorporates the hydraulic fracture propagation process during the initial fracturing and dynamic stress changes during the initial production process. It employs artificial intelligence algorithms to calibrate the wellhead treating pressure using physics-based model, enabling a better understanding of the initial fracturing fracture geometries. The production history match is then conducted based on the initially calibrated hydraulic fracture geometries, preserving the precision of the original fracture geometry. Additionally, geomechanics modeling is conducted to obtain dynamic stress changes during the initial production process. For the refracturing design, the fracture propagation model for the refracturing process is later conducted on the depleted stress field. Following a 240-day period after refracturing, the production history is matched using an artificial intelligence-assisted reservoir simulator. Our results indicate that due to prolonged production, significant changes occur in the stress field during the initial development period, with an average horizontal stress deviation angle of approximately 35 degrees in the near-well zone. With the combined influence of the changing stress field and natural fractures, refracturing results in longer and more complex hydraulic fractures geometries, ultimately increasing individual well production.