受多级海平面控制的早成岩期岩溶发育模式——以鄂西渝东——湘鄂西地区石龙洞组为例  

An eogenetic paleokarst model controlled by multi-level sea-level:A case study of Shilongdong formation in Lower Cambrian,from the west Hubei and the east Chongqing to the west Hunan and Hubei,SW China

作　　者：卢朝进 刘震[1,2] 田海芹 刘明洁[4] 林娟华[3] 王媛 杨晓光 LU Chaojin;LIU Zhen;TIAN Haiqin;LIU Mingjie;LIN Juanhua;WANG Yuan;YANG Xiaoguang(College of Geosciences,China University of Petroleum,Beijing 102249,China;State Key Laboratory of Petroleum Resources and Propecting,Beijng 102249,China;Petroleum Exploration and Production Research Institute of SINOPEC,Beijing 100083,China;State Key Laboratory of Oil and Gas Geology and Exploitation,Southwest Petroleum University,Chengdu,Sichuan 610500,China;School of Energy Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中国石油大学(北京)地球科学学院,北京102249 [2]中国石油大学油气资源与探测国家重点实验室,北京102249 [3]中国石油化工股份有限公司石油勘探开发研究院,北京100083 [4]西南石油大学地球科学与技术学院,四川成都610500 [5]中国地质大学(北京)能源学院,北京100083

出　　处：《中国矿业大学学报》2018年第5期1055-1067,共13页Journal of China University of Mining & Technology

基　　金："十二五"油气重大专项(2011ZX05005)

摘　　要：综合野外露头、薄片、阴极发光、碳氧同位素和测井资料对鄂西渝东—湘鄂西地区下寒武统石龙洞组岩溶发育特征进行研究,并对其岩溶发育模式及控制因素进行分析.在石龙洞顶部识别出发育于古洞穴中的钟乳石;古岩溶风化壳被划分为基岩、弱风化层、强风化层、溶塌层和风化黏土层;发育两类岩溶角砾:一类是富含基质的碎屑支撑岩溶角砾,另一类是基质支撑岩溶角砾;而在石龙洞组下部3个四级层序的顶部颗粒滩中,发育典型的相控溶蚀充填特征,可以识别出基岩带、半解离带和混合充填带;且早期海底纤维状胶结物被溶蚀;悬垂状方解石胶结物和岩溶角砾的发育.研究结果表明:石龙洞组发育多期次的早成岩期岩溶作用.碳氧同位素特征表明,岩溶带中的δ^(13)C为-3.7‰^-0.3‰,δ^(18)O为-10.6‰^-8.5‰,较非岩溶带中的碳氧同位素值偏负.在石龙洞组的每个四级层序顶部的高渗透层中,均受到淡水成岩作用的改造;横向上,在PSQ1-PSQ3时期,岩溶带只局限于丁寨剖面,在PSQ4时期,岩溶带广泛发育于整个台地,故在PSQ1-PSQ3时期,岩溶类型为海岛型;在PSQ4时期,岩溶类型为海岸型.在米兰科维奇理论的指导下,建立了米兰科维奇旋回与四级海平面变化的响应关系,表明多期次发育的早期岩溶受到米兰科维奇旋回对四级海平面变化控制的影响.本模式的建立对四川盆地周缘地区油气勘探的部署和岩溶发育模式的丰富均有一定指导意义.This study utilized field outcrops,thin sections,cathode luminescence,carbon and oxygen isotopes,and logging data to investigate the development model of paleokarst within the Shilongdong formation in Lower Cambrian,from the west Hubei and the east Chongqing to the west Hunan and Hubei area.The results show that the karst in the upper part of the Shilongdong formation is characterized by the dripstones developed within paleocaves,the paleoweathering crust with four zones（bedrock,weakly weathering zone,intensely weathering zone and solution collapsed zone）in vertical,and two types of breccia（matrix-rich clast-supported chaotic breccia and matrix-supported chaotic breccia）.While in the lower part of the Shilongdong formation,the typical facies controlled dissolution and filling,dissolved-fibrous cement,crescent microspar cement and breccia in the high-permeability grainstone of the upper part PSQ1—PSQ3indicate the development of the multi-phase eogenetic karst.The variations of the carbon and oxygen isotope suggest the development of the meteoric diagenesis in Shilongdong formation,which is characterized by the values of δ13C and δ18O respectively ranging from-3.7‰to-0.3‰and-10.6‰to-8.5‰.Laterally,the karstification only occurs on the Dingzhai section from PSQ1—PSQ3,but widely distributes through the whole platform in PSQ4,which demonstrates that the development of paleokarst model is the island model in PSQ1—PSQ3and coastal model in PSQ4.Milankovitch cycle interprets that the fluctuation of the forth-order sea-level generates the multi-stage eogenetic karst.The paleokarst model is an important step towards a better understanding of the link between probably orbitally forced sea-level oscillations and eogenetic karst in Lower Cambrian.This paleokarst model provides guidance to the exploration of oil and gas in adjacent areas of Sichuan basin.

关 键 词：早成岩期岩溶 岩溶模式 高频海平面 石龙洞组 下寒武统 鄂西渝东—湘鄂西 

分 类 号：TE122[石油与天然气工程—油气勘探]