四川盆地中二叠统栖霞组、茅口组岩相古地理及勘探方向

通过地层剥蚀关系分析,四川盆地中二叠统沉积前的古构造格局具有"三隆一洼"的特点。基于野外剖面、岩心和薄片观察,结合录井、测井相和地震相分析,明确了栖霞组和茅口组发育镶边碳酸盐岩台地沉积,包含一级台缘带、二级台缘带、开阔台地和台盆等4种亚相以及一级台缘滩、二级台缘滩、台内滩和硅质台盆等微相。栖霞组、茅口组岩相古地理受控于沉积前古构造:一级台缘带分布于古隆起与斜坡—盆地过渡地带;开阔台地分布于古隆起区和低隆起区;台盆分布于低洼区;二级台缘带分布于开阔台地和台盆之间的过渡地带。类比上二叠统长兴组和下三叠统飞仙关组油气勘探,栖霞组、茅口组台地内部的二级台缘带可作为下一步油气勘探的有利领域。

Lithofacies Paleogeography and Exploration Realms of Middle Permian Qixia Formation and Maokou Formation,Sichuan Basin

According to the relation to strata erosion, the paleotectonic framework of three uplifts and one sag developed before Middle Permian in Sichuan Basin. Based on field profile, core, thin-section, logging data, and seismic facies analysis, it is claimed that carbonate rimmed platform develope in Qixia Stage and Maokou Stage, in which some subfacies developed such as platform margin, open platform and platform basin, furtherly more microfacies can be identified including platform margin beach, inner-platform beach and siliceous platform basin. Controlled by paleotectonic framework, platform margin developed along the transition zone between the old uplift and slope-basin or between open platform and platform basin. Open platform developed in the old uplift and low uplift. Platform basin developed in the low sag. Comparing with the oil and gas exploration in Upper Permian Changxing Fm. and Lower Triassic Feixianguan Fm., it is suggested that the platform mar-gin formed during Qixia Stage and Maokou Stage would be the next favorable exploration realms.