Influence of Tectonic Activity Characteristics of the Permian–Triassic and Jurassic on Oil and Gas Migration Efficiency in the Luzhou Area—A Case Study of Fault Characteristics

In order to clarify the controlling effects of tectonic activity on hydrocarbon migration efficiency in the Permian–Triassic strata of the Luzhou area, Sichuan Basin, this study takes faults as the research objective. Using 3D seismic data, tectonic evolution records, and single-well test data, we systematically analyze the geometric characteristics, activity phases, classification by grade and type, and reservoir-controlling effects of faults. The results show that a total of 843 reverse faults have been identified in the study area. The major faults are distributed in a NE-SW trend, with eight planar combination styles developed, and the main cross-sectional styles are back-thrust and “Y”-shaped types. The faults experienced four phases of tectonic activity: Caledonian, Hercynian, Indosinian, and Yanshan–Himalayan. Among these, the Indosinian phase is the key formative phase, effectively connecting the source rocks and reservoirs. The faults are classified into three grades and four categories: source-connected faults, reservoir-modifying faults, damaging faults, and source-connected and damaging faults. Migration efficiency is jointly controlled by fault grade, activity phases, and the penetrated formations. Among them, third-order source-connected faults formed during the Indosinian phase exhibit the highest migration efficiency, while first-order damaging faults formed during the Yanshan phase tend to cause hydrocarbon dissipation. This study can provide a reference for hydrocarbon exploration and the prediction of favorable areas in the Luzhou area.