岩相古地理对自贡地区嘉陵江组储层的控制

THE CONTROL OF LITHOFACIES PALEOGEOGRAPHY TO JIALINGJIANG FORMATION RESERVOIR IN ZIGONG AREA

通过对四川盆地自贡地区早三叠世嘉陵江期沉积背景和沉积特征的分析,认为本区嘉陵江组受海平面升降变化的影响,发育了许多不同级次的沉积旋回。只有在每个海平面变化旋回的上升晚期—下降早期与每个海水咸化旋回的早期—中期的有序配置时期,才是嘉陵江组储层发育的有利时期,储层主要发育于嘉二3、嘉四1、嘉四3和嘉五1亚段。整个嘉陵江组最有利的储集相带是砂屑滩和云坪微相,其平均孔隙度较高,基本在5%以上,其次为云质泻湖微相,表明嘉陵江组层状储层的发育严格受沉积微相控制。海底微地貌起伏的复杂性决定了沉积微相的平面分布出现变化多端的分异,导致沉积微相所决定的储层在早期就具有显著的宏观非均质性。

Through the analysis of depositional setting and Characteristics of Jialingjiang period,early Triassic in Zigong area of Sichuan Basin,it is recognized that most sedimentary cycles with difference steps have been developed by the affect of sea level fluctuation change.It is the best development time of Jialingjiang Formation reservoir only in the period of ordered configuration which is between the late increased to early decrease of every sea level change cycle and early-middle time of every sea salinity cycle.The reservoir mainly develops on the Jia21 Sub-member,Jia41 Sub-member,Jia43 Sub-member and Jia51 Sub-member.The favorite reservoir microfacies is the sand-size intraclast shoal and dolomite flat microfacies in the whole Jialingjiang Formation,its average porosity is quite high,over 5%,followed by dolomite lagoon microfacies,which shows that the development of the bedded reservoir distribution is controlled by sedimentary microfacies.The complexity of microrelief in bottom determine that the plane distribution of microfacies has variegated differentiation.And it leads to the reservoir which is determined by microfacies has obvious macroscopic heterogeneity at the early time.