川中地区前震旦系裂谷研究及其地质意义

2011年四川盆地高石1井在震旦系灯影组获得天然气勘探重大突破后,为了明确川中地区震旦系—下古生界构造—沉积演化、储层和油气分布的控制因素,深化地质认识,寻找规模储量,对前震旦系进行了深入研究。运用三维连片地震资料,辅以重磁电、露头、钻井、测井和岩心等资料,结合前人的地质认识,综合分析认为川中地区可能存在前震旦系裂谷。研究表明:前震旦系裂谷盆地边界断裂继承性活动和差异沉降,控制了该区震旦系台缘带的发育、展布及下古生界地层的沉积与演化;桐湾运动和加里东运动,震旦系裂谷期大断裂继承性活动,形成北西向、北东向等多组直立正断裂;裂谷内部的油气以活化的裂谷断层作为通道运移到裂谷系上覆地层圈闭中聚集成藏,形成良好的"下生上储上盖"式天然气成藏组合。该研究成果为全面、准确地评价该区前震旦系裂谷对上覆地层的控制作用以及深层的天然气勘探开发潜力提供了技术支撑。

Geological research and significance of a rift valley in the Presinian period in central Sichuan Basin

Since the breakthrough was made by the Gaoshi 1 Well in 2011 in the Sinian Dengying Fm reservoirs, a further research has been conducted into the Presinian System to figure out the structure sediment evolution, and the controlling factors of the reservoirs and the hydrocarbon distribution in the Lower Palaeozoic Erathem in central Sichuan Basin. Combined with the previous geological understandings, the comprehensive analysis conducted based on the 3D seismic data in combination with heavy magnetoelectricity, outcrop, drilling, logging, and core data, showed that there may exist a rift valley in the Presinian period in central Sichuan Basin. The study also indicated that the successive breakage and differential settlement on the edge of the Presinian rift valley basin controlled the development and distribution of terrace marginal area within the Presinian system and the settlement and evolution of the Lower Palaeozoic strata; vertical breakages in the northwest and northeast directions were caused by the Tongwan and Caledonian Movements and the successive faults were thus formed in the valley rift period; and the oil & gas within the rift moved to the overlying strata through the rift valley faults and were accumulated in such favorable gas pools with good "lower kitchen upper reservoir upper caprock" assemblage. This study provides robust technical support for the comprehensive and accurate assessment of the Presinian rift valley's control over the overlying strata as well as for deep reaching exploitation.