川中龙岗地区下侏罗统大安寨段沉积相分析及有利储集层预测

应用钻井、测井和地震等资料对川中龙岗地区下侏罗统大安寨段的沉积相类型及其展布特征进行了研究,将大安寨段的湖泊相沉积划分为4个亚相及若干微相。大安寨段沉积时期的沉积展布及演化主要受湖平面升降控制,经历过一次较大规模的水进水退旋回:大三沉积时期发生水进,主体为浅湖—半深湖沉积;大一三沉积时期水体最深,主体为半深湖沉积;大一三沉积晚期发生水退,到大一沉积晚期湖平面已降至较低水平,主体为滨浅湖沉积,介壳灰岩发育。沉积相带在平面上具有明显的环带状展布特征,据此建立了大安寨段沉积模式。大一段主要发育5个介壳滩,是最有利于储集层发育的沉积相带。储集岩类型主要为介壳灰岩和泥质介壳灰岩,结合裂缝发育分析,预测了3个有利储集层区带。

Sedimentary facies and reservoir prediction of the Lower Jurassic Da'anzhai Member,Longgang area,central Sichuan Basin

Based on integrated application of drilling,logging and seismic data,the types of sedimentary facies and their distribution in Da'anzhai Member in Longgang area were studied. The lacustrine sediments of Da'anzhai Member were divided into 4 subfacies and several microfacies. Sedimentary distribution and evolution in the study area were mainly affected by lake-level fluctuation during the Da'anzhai period,experiencing a large-scale water transgression and regression. During the period of the third submember of Da'anzhai,water transgression occurred,the deposits were mainly shallow and semi-deep lacustrine. During the period of the first-third submember of Da'anzhai,the water was the deepest,the deposits were mainly of semi-deep lacustrine. Then,water regression occurred,lake-level dropped to a very low stand,the deposits were mainly shore-shallow lacustrine. Sedimentary facies distributed obviously in a ring shape on the plane,whereby the sedimentary facies model of Da'anzhai Member were established. There were mainly five shelly shoals in the first submember of Da'anzhai,which were the most conducive to the formation of reservoirs. The main types of reservoir rocks were shelly limestone and argillaceous shelly limestone. Combined with fracture analysis,three favorable reservoir zones were predicted.