四川盆地及周缘寒武系洗象池组层序-岩相古地理演化与天然气有利勘探区带

综合利用钻井、测井、露头剖面、岩心和地震等资料,对四川盆地及周缘地区寒武系洗象池组层序-岩相古地理开展综合研究.研究结果表明:①研究区洗象池组主要为碳酸盐岩台地沉积环境,自西向东依次发育混积潮坪、局限台地、开阔台地、台地边缘、斜坡—盆地相沉积.应用层序地层学方法可将洗象池组自下而上划分为5个三级层序(SQ1—SQ5)....

Sequence-based lithofacies paleogeography and favorable natural gas exploration areas of Cambrian Xixiangchi Formation in Sichuan Basin and its periphery

Drilling logs,outcrop profiles,cores and seismic data were used to study the sequence-based lithofacies palaeogeography of Cambrian Xixiangchi Formation in Sichuan Basin and its periphery.The results show that:(1)Xixiangchi Formation was dominated by carbonate platform facies,in which mixed tidal flat,restricted platform,open platform,platform margin,and slope-basin units were developed from west to east.By applying the principles and methods of sequence stratigraphy,the Xixiangchi Formation was divided into five third-order sequences(SQ1-SQ5)from bottom to top.(2)The restricted platform was the dominant sedimentary facies type in Xixiangchi Formation,which can be subdivided into three sedimentary subfacies,namely platform,intra-platform shoal,and semi-restricted lagoon.The intra-platform shoals were distributed in points in the early stage,and later as the shoals increased in size,they were of continuous distribution.(3)There are two kinds of reservoirs of granular dolomite and crystal dolomite in Xixiangchi Formation,and the overall physical properties are characterized by low to extra-low porosity and permeability.The development of high-quality reservoirs was controlled by shoal facies deposition,dissolution reformation and fracturing action.The reservoir thickness is generally thin,but the vertical cumulative thickness mainly ranges from 5 to 40 m.The horizontal distribution of reservoirs is of poor continuity,and is concentrated in southern,eastern and northeastern Sichuan Basin.(4)There are five favorable exploration targets developed in Xixiangchi Formation in Sichuan Basin,which are located in the central Sichuan paleo-uplift,Weiyuan paleo-uplift,eastern to southeast Sichuan and northeastern Sichuan.The available exploration area exceeds 20000 km²,which serves as a potential reserve exploration area in Sichuan Basin.