摘要
Tectonic stress is one of the comparatively active energies in the earth’s crust.It is of guiding significance in oil and gas exploration and development to study tectonic stress patterns and transformation processes.Through studies on upright folds,conjugate joints,slickenside on fracture planes and other structural vestiges,we rebuilt the Late Mesozoic-Cenozoic tectonic stress field of Xuanhan-Daxian region and examined regular patterns of its tectonic activities.The result shows that this region experienced at least two tectogeneses in Late Mesozoic-Cenozoic,one occurred during Late Yanshanian,when a series of NE-direction faults and folds developed in Xuanhan region of east Sichuan under the SE to NW direction compression;and the other happened in Himalayan period,when the east Sichuan tectonic belt subsided gradually while NW-direction faults and folds were formed by the NE to SW direction extrusion in Daba mountain.The superposition of various tectonic stress fields with different directions and intensities in different periods comprehensively controlled the formation and evolution of oil and gas reservoirs of this region.The superimposition of staggered tectonic activities in the study area has improved reservoir properties,substantially controlled the development of hydrocarbon traps and adjusted lithologic reservoirs into structural-lithologic composite ones.Moreover,tectonic stress and fractures formed consequently in rocks have provided oil and gas migration with dynamic power and pathways.