川东五百梯长兴组台缘生物礁储层沉积学特征

Sedimentary characteristics of platform margin reef reservoir of Upper Permian Changxing Formation in Wubaiti area, eastern Sichuan

川东五百梯地区长兴组发育台内海槽、台地前缘缓斜坡、台地边缘生物礁滩和开阔台地4个相带,其中环海槽发育的台地边缘相带贯穿整个川东地区并绵延数百公里,是寻找生物礁滩型气藏最有利的相带。以五百梯地区长兴组台地边缘生物礁滩为例,可将其划分为礁基、礁核、礁顶、礁前和礁后等诸亚相,其中最有利储层发育的亚相为礁核和礁顶亚相,储集岩主要为礁滩相白云岩及晶粒白云岩。在地震剖面中利用丘状杂乱反射和气烟囱效应可对礁相储层进行有效预测,白云岩化和溶蚀作用是控制礁型气藏形成的关键因素,也是形成优质礁相储层的基础,而裂缝则大大提高了储层的孔、渗性。

There are four facies belts developed in Changxing Formation in Wubaiti area,including intraplatform trough （deep water basin）,platform slope,platform margin reef flat and open platform.The platform marginal facies of continental shelf around intraplatform trough developed well.It is across entire eastern Sichuan and extends hundreds of kilometers,and it is the most important facies for seeking reef gas reservoir.The platform margin reef in Wubaiti area can be divided into five subfacies,including reef base,reef core,reef crest,reef front and reef behind,among which reef core and reef crest are the most favorable subfacies for the reservoir development.The reservoir rocks are mainly dolomite of reef and shoal facies and grain dolomite.Hummocky disorder reflection and chimney effect in seismic profile can be used to effectively predict reef reservoir.Dolomitization and dissolution are not only the key factors for controlling the forming of reef gas reservoir,but also the basis for forming high quality reef reservoir.The fracture raises the porosity and permeability of reservoir.