| 川中地区中二叠统栖霞组滩控岩溶型白云岩储层特征及主控因素 |
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| 引用本文： | 芦飞凡,谭秀成,王利超,唐青松,肖笛,董少峰,苏成鹏,潘政屹.川中地区中二叠统栖霞组滩控岩溶型白云岩储层特征及主控因素[J].沉积学报,2021,39(2):456-469. |
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| 作者姓名： | 芦飞凡 谭秀成 王利超 唐青松 肖笛 董少峰 苏成鹏 潘政屹 |
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| 作者单位： | 油气藏地质及开发工程国家重点实验室,西南石油大学,成都 610500;中国石油天然气集团有限公司碳酸盐岩储层重点实验室西南石油大学研究分室,成都 610500;油气藏地质及开发工程国家重点实验室,西南石油大学,成都 610500;中国石油西南油气田分公司气田开发管理部,成都 610051;表生地球化学教育部重点实验室,南京大学地球科学与工程学院,南京 210023;中国石油西南油气田分公司勘探开发研究院,成都 610041 |
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| 摘 要： | 四川盆地中部地区栖霞组的白云岩是该区主要储层，储层成因的主流观点是热液白云岩化。目前勘探实践发现，优质储渗体形成与早期相控岩溶作用有关。通过取芯及测录井资料进行了详细分析，研究结果表明，该类白云岩储层主要位于栖霞组中上部颗粒滩发育的地层中，按其宏微观产出状态可分为溶斑状云岩、溶洞充填云岩、针孔状基质云岩和致密基质云岩。储集岩物性以溶洞充填云岩最佳，储层类型属裂缝—孔洞型储层。进一步分析显示:研究区栖霞组滩相地层沉积后随即经历了一定时间的整体抬升暴露，期间接受早成岩期岩溶作用，形成了具相控特征的岩溶系统，早期淡水岩溶作用是优质孔洞型储层形成的关键。在中二叠沉积期后不久的东吴运动高峰期，热液流体上涌将岩溶系统及其部分围岩交代为白云岩。由于岩溶系统内部保留了较多的残余自由空间，经热液白云岩化调整后形成的白云石更为自形，且保存了较多的晶间孔隙。而相比之下，岩溶系统基岩已在早期埋藏中趋于致密，云化后形成的云岩物性较差。仅有部分颗粒岩仍然保留了一定的原始孔隙，云化后针孔较为发育。栖霞组白云岩储层具有相控性，规模性和继承性三大发育特点。提出优质储层分布受控于岩溶系统，为区内栖霞组白云岩储层成因提供了新的思路，对该区储层分布预测及进一步的勘探部署也具一定指导意义。
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| 关 键 词： | 四川盆地 栖霞组 颗粒滩 早成岩期岩溶 热液白云岩化 储层特征 |
| 收稿时间： | 2019-10-08 |
Characteristics and Controlling Factors of Dolomite Reservoirs within Shoal-controlled Karst in the Middle Permian Qixia Formation,Central Sichuan Basin |
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| LU FeiFan,TAN XiuCheng,WANG LiChao,TANG QingSong,XIAO Di,Dong ShaoFeng,SU ChengPeng,PAN ZhengYi.Characteristics and Controlling Factors of Dolomite Reservoirs within Shoal-controlled Karst in the Middle Permian Qixia Formation,Central Sichuan Basin[J].Acta Sedimentologica Sinica,2021,39(2):456-469. |
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| Authors: | LU FeiFan TAN XiuCheng WANG LiChao TANG QingSong XIAO Di Dong ShaoFeng SU ChengPeng PAN ZhengYi |
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| Institution: | (State Key Laboratory of Oil and Gas Geology and Exploitation,Southwest Petroleum University,Chengdu 610500,China;Department of Key Laboratory of Carbonate Reservoirs of CNPC,Southwest Petroleum University,Chengdu 610500,China;Gas Field Development and Management Department,PetroChina Southwest Oil&Gasfield Company,CNPC,Chengdu 610051,China;Key Laboratory of Surficial Geochemistry,Ministry of Education,School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China;Exploration and Development Research Institute,PetroChina Southwest Oil&Gasfield Company,CNPC,Chengdu 610041,China) |
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| Abstract: | The dolomites of the middle Permian Qixia Formation form the main reservoir in the study area.Further examination has shown that the reservoir formation is related to shoal facies-controlled eogenetic karst.Data from core analysis indicates that reservoirs occur mainly in the grain shoal stratum located in the middle-upper part of the Qixia Formation,and are divided into four types depending on the macro-and micro-occurrences of dolomites:(1)porphyritic dolomite derived from weakly re-formed karst;(2)dolomitic karst filled by strongly re-formed karst;(3)dolomite with pinhole-like features that has retained the pore structure of the original grain shoal;and(4)a compact dolomitic matrix.Of these,dolomitic karst-filled reservoirs have the best physical properties.The dolomite reservoir in the Qixia Formation is of the fracture-porosity type.Analysis shows that the shoal facies strata in the study area experienced a period of uplift and exposure immediately after sediment deposition,resulting in early diagenetic karstification which formed facies-controlled karst systems.These systems,along with residual pores in the granular limestone,became the fluid pathways for dolomitization.Porphyritic dolomite,dolomitic karst fillings,‘pinhole’dolomite and some of the compact dolomitic matrix are the result of hydrothermal dolomitization which took place after the depositional stage in the middle Permian,thus retaining abundant intercrystalline pores in the karst system.The crystalline dolomite tends to be automorphic,largely due to the presence of voids within the karst.By contrast,the matrix surrounding the karst systems was densely compacted in the early burial stage,and subsequent dolomitization produced dolomite with poor physical properties.A small proportion of the grainstone retained some of the original pores,forming the‘pinhole’dolomite.The study reveals that the Qixia Formation dolomite reservoirs are characterized by facies control,scale and inheritance,and that the presence of high-quality reservoirs is due to the karst system.This new concept of the genesis of Qixia Formation dolomite reservoirs is significant for guiding the prediction of reservoir distribution and further exploration and deployment in this area. |
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| Keywords: | Sichuan Basin Qixia Formation grain shoal eogenetic karst hydrothermal dolomitization reservoir characteristics |
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