Quantitative Prediction of Tectonic Fractures Coupled with Minimum Energy Dissipation and Least Action Principles: A Case Study of Keshen 8 Area, Kuqa Depression

Tectonic fractures refer to a series of discontinuities formed in crustal rocks under the action of tectonic stress, serving as a key factor governing numerous geological processes and resource exploitation. In the field of oil and gas exploration, especially for the tight sandstone reservoirs in the Kuqa Depression of the Tarim Basin, the tectonic fracture system acts as the primary seepage pathway and reservoir space, directly determining the distribution of reservoir "sweet spots" and single-well productivity. To achieve quantitative characterization of reservoir fractures and accurate prediction of their spatial distribution, we innovatively introduced the principle of minimum energy dissipation and the principle of least action, which reflect the essential laws of nature. By fully integrating the complex tectonic evolution process with classical mechanics theory, we completed the quantitative prediction research on fractures during complex tectonic evolution based on four-dimensional (4D) dynamic stress field simulation. Based on the analysis of tectonic evolution history in the Keshen 8 area of the Kuqa Depression, combined with extensive field, seismic, core and logging data, as well as rock mechanics experiments and acoustic emission experiments, a reasonable paleotectonic geomechanical model was established. From a novel perspective, we introduced the principle of minimum energy dissipation and the principle of least action, and further combined them with classical mechanics theory and the variational principle of continuum media. A time-domain dynamic rock failure criterion and a fracture parameter characterization model were constructed, building a "bridge" between stress and fracture parameters. By selecting an optimal elastoplastic finite element simulation platform and setting appropriate time steps, we completed the time-domain 4D tectonic stress field simulation. On this basis, we implanted Python programs into the finite element simulation platform, realizing the quantitative prediction of the spatial distribution of reservoir fractures in the Keshen 8 area of the Kuqa Depression. The prediction results indicate that folding is the primary controlling factor for fracture development in the Keshen 8 gas reservoir. On the plane view, the linear fracture density in the structural high parts of the east-west anticlines is slightly higher than that in the saddle parts and both limbs, and the linear fracture density in the core of the eastern anticline is higher than that of the western anticline. The fracture dip angle gradually decreases from the structural high points to the two limbs of the anticlines. The prediction results are in high agreement with the actual well-point measurement data and production performance data. High-yield wells are basically located in fracture-developed zones with high linear density and near-vertical dip angles.