川南地区渐变型盆—山边界条件下龙马溪组页岩气（藏）富集主控因素：构造—沉积分异与差异性演化

梁 霄^1，2  徐剑良¹  王 滢¹  方新焰³
赵 磊¹  伍翊嘉¹  邓 宾²
（1. 中国石油集团川庆钻探工程有限公司，地质勘探开发研究院 成都 610051；2. 油气藏地质及开发工程
国家重点实验室，成都理工大学 成都 610059；3. 有机地球化学国家重点实验室，
中国科学院广州地球化学研究所 广州 510640）

摘要: 川南地区龙马溪组全面进入3 500 m以浅的页岩气开发、上产关键阶段。油气地质学界长期以来针对页岩岩相、岩石学与孔隙特征等储层静态参数的重视以及对龙一₁¹小层的单一层系开发的局限，对川南地区龙马溪组页岩气整体产能的提高产生了一定制约。回归基础地质本质，采用地质—地球化学综合研究思路，以构造控制下的沉积分异格局为框架，补充完善川南地区笔石生物地层划分体系；依靠多期节理构造与古应力反演等构造解析方法，建立川南渐变型盆—山边界条件下龙马溪组多期构造演化与流体温压模型，明确川南地区复杂构造背景下页岩气差异富集机理。奥陶纪—志留纪之交的“三隆一坳”古构造—沉积分异，控制了川南地区五峰组—龙马溪组优质页岩渐进式发育与分布。在川南—大娄山渐变型盆山结构边界条件下，晚白垩世以来所经历的4期不同应力场构造变形事件，使威远、泸州—大足与长宁—宁西地区五峰组—龙马溪组具有差异性构造变形—抬升剥蚀与演化特征。差异性的埋深—隆升过程，对受埋深与构造热事件控制的页岩有机地球化学特征及流体充注体系产生重要影响。构造—沉积分异、盆山建造与热演化过程，最终控制川南地区五峰组—龙马溪组早期有限聚集—中期相对富集—晚期调整改造的页岩气成藏演化过程。                                                           

Abstract: The Longmaxi Formation in the southern Sichuan Basin has entered a critical stage of shale gas development and production with depth of less than 3 500 m. The petroleum geologist has long attached importance to the static parameters of reservoirs such as shale lithofacies, petrology and pore characteristics, and the limitation of the development of a single layer of the S₁l¹. The increase in production capacity has created greater constraints. Returning to the basic geological essence, using comprehensive geological-geochemical research ideas, taking the sedimentary differentiation pattern under structural control as the framework, supplementing and perfecting the biolithic stratigraphic division system in southern Sichuan, relying on multi-phase joint structure and palaeostress inversion and other structural analysis method, finally establishing a multi-phase structural evolution and fluid temperature and pressure characteristic model of Longmaxi Formation under the boundary conditions of basin-mountain structure in the south of Sichuan, which can effectively form the shale gas difference enrichment mechanism in the same area in South Sichuan. Tectono-depositional differentiation of ‘Palaeouplift-Depression’ during Ordovician-Silurian has controlled the progressive development and distribution of high-quality Longmaxi shale in the southern Sichuan Basin. The four phases of tectonic deformation events experienced in different fields have given the Longmaxi Formation in Weiyuan, Luzhou-Dazu, and Changning-Ningxi areas with differential structural deformation-lifting erosion and evolution characteristics. Differential construction process of burial depth-uplifting has an important impact on shale organic geochemical characteristics and fluid filling system controlled by burial depth and tectonic thermal events. Tectono-depositional differentiation, basin-mountain construction, and thermal evolution ultimately control the Longmaxi Formation shale gas accumulation evolution process in the early limited accumulation-mid relative enrichment-late adjustment and transformation in the southern Sichuan area.

Key words: Sichuan Basin   Shale gas   Enrichment mechanism    Basin-mountain construction    Tectono-depositional differentiation Thermal evolution

关键词:  四川盆地  页岩气  富集主控因素  构造—沉积分异  盆—山建造  热演化

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