四川盆地震旦系岩相古地理及有利储集相带特征

Lithofacies palaeogeographic characteristics and favorable reservoir facies belts of the Sinian in the Sichuan Basin

四川盆地震旦系是我国最古老的含油气层系之一,历经了60多年的勘探研究,先后发现了威远气田和资阳含气构造,近期又取得了天然气勘探突破。为了对该区有利储集相带的分布进行预测和评价,基于前人的研究成果,详细分析了震旦系露头、岩心和钻井资料,结合大量分析化验数据,对震旦系沉积相和岩相古地理进行了研究。结果表明:①以桐湾运动和澄江运动所形成界面为界,可将震旦系划分为陡山沱组和灯影组,陡山沱组以砂泥岩沉积为主,灯影组以厚层白云岩沉积为主;②灯影组主要发育潮坪相,潮坪包括泥云坪、藻云坪、膏盐坪、颗粒滩和灰泥坪;③陡山沱组以陆棚相沉积为主。结论认为:灯影组在四川盆地内部大面积发育白云岩坪和颗粒滩两类有利的储集相带,为盆地内储层大面积分布提供了物质基础,优质储层在威远、资阳、高石梯、磨溪、安平店和盘龙场等地区较为发育,储层分布面积约6×104 km2。

The Sinian strata in the Sichuan Basin are one of the oldest hydrocarbon-bearing sequences in China.The Weiyuan gas field and Ziyang gas-bearing structure have been discovered successively over the last 6 decades of exploration and recently a new gas discovery was obtained again.In order to predict and evaluate the favorable reservoir facies belts in this study area,we first analyzed in detail the outcrops,core and drilling data from the previous research results,then studied the sedimentary facies and lithofacies palaeogeography in combination with test data.The Sinian strata in this area consist of the Doushatuo Formation dominated by sandstones and mudstones and the Dengying Formation dominated by thick dolomites.The main sedimentary facies of the Dengying Formation is tidal flat which can be subdivided into argillaceous dolomitic flat,algal dolomitic flat,gypsum flat,grain beach and lime mudstone flat,while the Doushantuo Formation is dominated by shelf facies.The favorable reservoir facies belts of the Dengying Formation in the Sichuan Basin are dolomitic flat and grain beach.Quality reservoirs occur in areas such as Weiyuan,Ziyang,Gaoshiti,Moxi,Anpingdian and Panlongchang with a total area of 60 thousand km2.