长宁和泸州地区构造变形差异性及其对页岩气保存的影响

Differences in structural deformation and its influence on shale gas preservation in Changning and Luzhou areas

长宁和泸州地区是四川盆地南部页岩气勘探的重点区块,分别位于盆—山结构的不同部位,其自元古代以来遭受多期构造改造作用,构造变形特征复杂。通过对研究区龙马溪组底界构造的精细地震解释和岩心裂缝统计分析,对比了长宁和泸州地区的构造变形特征和多尺度断层、裂缝发育特征的差异性,恢复了古生界以来的构造演化过程,为页岩气保存条件评价提供了依据。研究表明:长宁地区构造样式以断层传播褶皱为主,主要构造变形时期为燕山晚期,并在喜山期遭受大规模抬升剥蚀;泸州地区为典型隔档式褶皱,主要构造变形时期为燕山早期,构造形迹在喜山期受到一定改造。泸州地区变形强度总体低于长宁地区,其断层级次和裂缝发育程度较低,页岩气保存条件较好。上述结果丰富了页岩气保存条件的理论研究,为下一步四川盆地页岩气开发提供了帮助。

Changning and Luzhou areas are key blocks for shale gas exploration in southern Sichuan Basin,which are located in different parts of the basin-mountain structure.Since the Proterozoic era,they have been subjected to multi-stage structural transformation,resulting in complex structural deformation characteristics.Through detailed analysis on the seismic fine structure and statistical analysis on the core fracture of the bottom boundary of Longmaxi Formation in the study area,the differences in structural deformation characteristics and multi-scale fault and fracture development characteristics between Changning and Luzhou areas are compared and the structural evolution process since the Paleozoic is restored,which provides a basis for the evaluation of shale gas preservation conditions.The research shows that the structural style of Changning area is mainly fault-propagation folds,with the main structural deformation period being the late Yanshanian period,and it has undergone large-scale uplift and denudation in the Himalayan period;Luzhou area is a typical barrier fold,of which the main structural deformation period is the early Yanshanian period,and its structural features were reformed to some degree in the Himalayan period.The deformation intensity of Luzhou area is generally lower than that of Changning area,having lower fault level,lower fracture development degree,and better shale gas preservation conditions.The above results enrich the theoretical research of shale gas preservation conditions and provide help for the next step of shale gas development in Sichuan Basin.