四川盆地下寒武统龙王庙组碳酸盐缓坡双颗粒滩沉积模式及储层成因  

Sedimentary model and reservoir genesis of dual grain banks at the Lower Cambrian Longwangmiao Fm carbonate ramp in the Sichuan Basin

作　　者：杜金虎 张宝民[2] 汪泽成[2] 邹才能[2] 徐春春[3] 沈平[3] 张健[3] 张静[2] 周慧[2] 姜华[2] 文龙[3] 单秀琴[2] 刘静江[2] 

机构地区：[1]中国石油勘探与生产分公司 [2]中国石油勘探开发研究院 [3]中国石油西南油气田公司

出　　处：《天然气工业》2016年第6期1-10,共10页Natural Gas Industry

基　　金：国家科技重大专项(编号:2011ZX05004);中国石油天然气集团公司勘探与生产专项"四川盆地乐山-龙女寺古隆起震旦系含油气评价及勘探配套技术研究"(编号:2012ZD01)

摘　　要：四川盆地下寒武统龙王庙组气藏是迄今我国发现的单体规模最大的特大型海相碳酸盐岩整装气藏。为剖析其沉积模式及储层成因,通过地质构造、沉积背景和沉积相综合研究与岩相古地理编图,发现自川西向渝东南地区,龙王庙组依次发育后缓坡混积潮坪、内/浅缓坡颗粒滩(上滩)—滩间海(洼地)、内缓坡台凹开阔较深水海湾→蒸发潟湖→蒸发潮坪、中缓坡风暴岩—障壁滩—丘滩(下滩)以及外缓坡—盆地相,并据此归纳总结出龙王庙组碳酸盐缓坡双颗粒滩沉积模式:1该模式以万州—宜宾台凹为轴,两侧古地貌高地水体浅、能量强而对称发育双颗粒滩,较之于经典模式,该模式新增了环绕古隆起发育的上滩,分布面积达8×10~4 km^2;2上滩沉积时所处古地貌位置最高、水体能量最强而滩体规模大,同生—准同生干热期、湿热期分别更易白云石化和遭受大气淡水溶蚀作用,尤其是得益于毗邻加里东—早海西期剥蚀尖灭线而更易遭受后表生期多期岩溶作用,因而规模优质储层更为发育;3多期大气淡水淋滤使得颗粒岩粒间孔和蠕形动物铸模孔溶蚀扩大,并叠加构造作用,从而形成颗粒滩相控、多旋回层状—准层状、裂缝—孔隙、蜂窝状孔洞型岩溶储层。The gas reservoir of the Lower Cambrian Longwangmiao Fm in the Sichuan Basin is a supergiant integral marine carbonate gas reservoir whose single scale is currently the largest in China. In order to figure out its sedimentary model and reservoir genesis, its geologi- cal structures and sedimentary settings and facies were analyzed comprehensively and the lithofacies paleographic map was plotted. It is re- vealed that the following sedimentary facies are successively developed in the Longwangmiao Fm from West Sichuan to Southeast Chongq- ing： diamictic tidal flat at the back ramp, grain bank （the upper bank） at the inner/shallow ramp interbank sea （depression）, deeper open bay at the platform depression of inner ramp ~ evaporative lagoon ~ evaporative tidal flat, tempestite at the middle ramp-barrier beach-mud mound beach （the lower bank）, and outer ramp-basin. Accordingly, the specific sedimentary model of dual grain banks in the Longwangmiao Fm carbonate ramp was established as follows. Firstly, in this model, dual grain banks are symmetrically developed with Wanzhou-Yibin platform depression as the axis, on whose dual sides the paleohighs have shallow water bodies with strong energy. Compared with the clas- sical model, the new one has a new upper bank which is developed around the paleohighs covering an area of about 8×10^4 km^2. Secondly, the upper bank is large for its paleogeomorphology being located at the highest position with the strongest water energy during deposition. Therefore, it is prone to dolomitization and meteoric dissolution respectively during contemporaneous-penecontemporaneous hot-dry and hot-humid periods, and especially the Caledonian-Early Hercynian denudation wedge out tends to undergo post-supergene multiphase karst- ification. Therefore, quality reservoirs are more developed on scale. Thirdly, the intergranular pores and vermes moldic pores were dissolved and enlarged due to the multiphase atmospheric fresh water leaching, and together with tectonism, grain bank facies

关 键 词：四川盆地及周缘 早寒武世 碳酸盐缓坡 双颗粒滩 沉积模式 孔隙—蜂窝状孔洞型 岩溶储集层 

分 类 号：P618.13[天文地球—矿床学]