川东南涪陵地区基底断裂特征与油气成藏

为了明确川东南涪陵地区茅口组热液白云岩气藏富集规律,基于钻井、岩心和涪陵地区连片三维地震资料,分析了研究区基底断裂特征与形成演化及其对茅口组油气成藏的意义,建立了油气成藏模式。研究结果表明:研究区基底断裂剖面上发育“Y”字形与反“Y”字形、“花状”、直立状3种构造样式;平面上识别出15、15-1、16号3条基底断裂,均以北西—南东向展布为主;基底断裂纵向上具有分层特征,同时沿断裂走向又体现出分段差异性;15、15-1号基底断裂中、上构造层活动性强于16号基底断裂,15号基底断裂西段活动性强于中段和东段。基底断裂控制了茅口组油气藏的形成与分布;白云岩储层沿基底断裂两侧呈条带状展布,距基底断裂越近,下伏志留系烃源岩对茅口组成藏贡献越大,含气性越好,测试产量越高。综合研究区基底断裂、烃源岩和储层发育特征等,建立了“下生上储、双源供烃”油气成藏模式。研究成果对深化涪陵地区茅口组热液白云岩研究具有重要指导意义,同时可为其他基底断裂发育区油气成藏研究提供借鉴。

Basement Fault Characterization and Hydrocarbon Accumulation in Fuling of Southeastern Sichuan

In order to clarify the hydrothermal dolomite gas reservoir enrichment pattern of Maokou Formation, the basement fault properties, formation and evolution and their significance for the hydrocarbon accumulation in the Maokou Formation and establish a hydrocarbon accumulation mode. Research indicates that there are three tectonic styles in the basement fault cross section, including "Y" and reverse "Y" style, "flower style" and upright style. Three basement faults were identified laterally, including No.15, No.15-1 and No.16 basement faults, which all show a northwest to southeast distribution. The basement fault indicates stratified properties in the longitudinal direction and segmentation along the fault strike. The middle and upper tectonic layer activity of the basement fault No.15 and No.15-1 is higher than that of the basement fault No.16, and the west section activity is higher than that of the east section in the basement fault No.15. The basement fault controls the formation and distribution of Maokou Formation hydrocarbon reservoirs. The dolomite reservoirs show a zonal distribution along the two sides of basement fault. The underlying Silurian sourcerock contribution increases with the decrease of distance to the basement fault. The well test production increases with the increase of gas content. An "on-source accumulation, dual-source hydrocarbon supply" hydrocarbon accumulation mode was established by comprehensively considering the basement fault, sourcerock and reservoir development pattern. This research could provide certain guidance for further understanding the Maokou Formation hydrothermal dolomite in Fuling, and it can also offer certain reference for the hydrocarbon accumulation characterization in other basement fault development areas.