四川盆地南部中二叠统茅口组古岩溶地貌恢复及其石油地质意义  

The Restoration of Palaeokarst Geomorphology of Middle Permian Maokou Formation and Its Petroleum Geological Significance in Southern Sichuan Basin

作　　者：肖笛[1] 谭秀成[1,2] 山述娇 陈韵骐[1] 夏吉文[4] 杨坚[4] 周涛[1] 程遥[1] 

机构地区：[1]西南石油大学油气藏地质及开发工程国家重点实验室,成都610500 [2]中石油碳酸盐岩储层重点实验室沉积与成藏分室,成都610500 [3]中石油西南油气田分公司勘探开发研究院,成都610051 [4]中国石油西南油气田分公司蜀南气矿,四川泸州646100

出　　处：《地质学报》2014年第10期1992-2002,共11页Acta Geologica Sinica

基　　金：中国石油科技创新基金项目(编号2011D-5006-0105);国家重点基础研究发展计划(973计划)(编号2012CB214803)资助成果

摘　　要：中二叠统茅口组是四川盆地南部重要的天然气产层之一。在中二叠世末期由东吴运动引起的地层暴露和风化淋滤的影响下,茅口组海相碳酸盐岩发育了风化壳岩溶型储层,但其岩溶古地貌迄今未得到准确恢复,影响了对茅口组碳酸盐岩储层分布的正确认识。本文以录井、测井及岩心等资料的综合分析为依托,通过地层精确划分、对比以及等时地层格架的建立,在茅口组顶部侵蚀面上、下地层中优选并确定了长一段顶面和茅三段底面两个全区稳定分布的、近等时的地层界面作为恢复岩溶古地貌的基准面。在分别编制研究区残余地层等厚图和印模地层等厚图的基础上,采用残余地层厚度法和印模地层厚度法,运用Surfer软件分别恢复了研究区龙潭组沉积前的岩溶古地貌和长一段沉积后茅口组顶部潜山地貌。这两种方法恢复的茅口组顶部古地貌所反映的地形起伏变化和总体格局基本一致,可以划分出岩溶台地、岩溶斜坡和岩溶盆地3个二级地貌单元以及溶丘、残丘、丘丛、浅洼、浅谷等次一级地貌单元。指出岩溶台地主要以泸州古隆起为核心向四周展布,整体地势较平缓,山体多呈圆丘状,低矮坡缓,不发育峰丛地貌;岩溶斜坡分布于岩溶台地外围,其中的岩溶缓坡主要展布于研究区北部和东部,岩溶台地西缘则表现出岩溶陡坡地貌;岩溶盆地分布于研究区西南部的宜宾、沐川、绥江等地区,地势平坦,以平原地貌为主。茅口组岩溶古地貌单元与大型储集空间及油气产出状况关系的分析表明,岩溶古地貌控制了岩溶型储层的发育与分布,进而控制了天然气产量的分布。指出岩溶缝洞型储层在岩溶台地和岩溶斜坡上基本同等发育,岩溶台地为重点勘探的有利区带,岩溶陡坡带则是最有利的勘探区带。Maokou Formation of mid-Permian is considered as one of significant gas-producing formations in southern Sichuan Basin.Affected by the exposure and weathering leaching in Dongwu movement during the latest of mid-Permian period,a typical weathering crust karst reservoir occurred in the marine carbonate of Maokou Formation.However,with the absence of accurate restore of the palaeokarst geomorphology,the knowledge has been affected of carbonate reservoir distribution developing in the Maokou Formation.The present work mainly analyses materials from drilling,logging and cores,classifying and correlating stratigraphy precisely,establishing isochronous stratigraphic framework,then choosing and confirming two stratigraphic interfaces which are distributing stably and almost isochronously in the whole region as the base levels,namely the subface of Mao-3 Member（the 3rd Member of Maokou Formation）and the top surface of Chang-1 Member（the 1st Member of Changxing Formation）,for restoring palaeokasrt geomorphology in the upper and lower erosional surfaces respectively.Additionally,depending on the residual and impression strata thickness data,it mapped contour map of residual strata thickness and that of impression strata thickness,then restoring,with the software called ＂Surfer＂,the palaeoakarst geomorphology pre-depositing Longtan Formation and the geomorphology of buried-hill in the top of Maokou Formation post-depositing Chang-1 Member.The geomorphology restored from the uppermost Maokou Formation,reflects that the geomorphology fluctuation and overall framework are accordant with the two methods,which can be classified into 3secondary geomorphic units,containing karst platform,karst slope and karst basin,and the units can be further divided into sub-geomorphic units including soluble hillock,monadnock,hillock clump,shallow depression and shallow valley.It is suggested that the karst platform distributed in a radial pattern originated from Luzhou palaeo-uplift core,with the gently topography,hummocky hills,lo

关 键 词：古地貌恢复 风化壳岩溶 岩溶储层 茅口组 四川盆地南部 

分 类 号：P618.13[天文地球—矿床学] P931.5[天文地球—地质学]