| 鄂尔多斯盆地西部下古生界风化壳优质储集层发育规律及成因机制: 以桃2区块马家沟组马五1-4亚段为例* |
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| 引用本文： | 冯强汉,许淑梅,池鑫琪,舒鹏程,孔家豪,崔慧琪,马慧磊.鄂尔多斯盆地西部下古生界风化壳优质储集层发育规律及成因机制: 以桃2区块马家沟组马五1-4亚段为例*[J].古地理学报,2021,23(4):837-854. |
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| 作者姓名： | 冯强汉 许淑梅 池鑫琪 舒鹏程 孔家豪 崔慧琪 马慧磊 |
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| 作者单位： | 1.中国石油长庆油田分公司,陕西西安 710021;2.中国海洋大学海底科学与探测技术教育部重点实验室,山东青岛 266100;3.中国海洋大学海洋地球科学学院,山东青岛 266100;4.海洋高等研究院/深海圈层与地球系统前沿中心,山东青岛 266100 |
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| 基金项目： | *中国石油天然气股份有限公司长庆油田分公司科研技术攻关项目(编号:DSCQC-2019-370)资助 |
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| 摘 要： | 鄂尔多斯盆地下古生界马家沟组顶部遭受长期风化剥蚀,形成了以膏云岩为主的风化壳岩溶储集层。盆地西部包括桃2区块在内的马家沟组马五1-4亚段以(含)膏云岩、白云岩和灰云岩互层发育为主。借助岩心观察、偏光显微分析和扫描电镜超微分析,识别出多层成层分布的(含)膏云岩;通过对硬石膏、白云石和方解石等矿物的物理和化学性质对比研究,认为(含)膏云岩的膏模孔、扩溶膏模孔及与之伴生的胀缩微裂缝为主要储集空间,孔隙大小具有明显的自限性,受硬石膏结核和石膏晶体大小的制约;岩性((含)膏云岩)和沉积微相(潮上带(含)膏云坪)是储集层形成的先天物质基础和环境条件,并导致(含)膏云岩储集层的层控分布特征;4期溶蚀作用过程中,硬石膏晶体和结核的组构选择性溶蚀和阶段性充填,是储集层形成的关键过程;储集层为层状相控、受岩溶作用影响,但岩溶地貌对储集层分布不再有决定性控制作用。(含)膏云岩发育区分散流的弥散性渗透溶蚀是大洞大缝不发育的主要原因。“层状相控岩溶作用岩性气藏”观点的提出将促使研究区下古生界从“岩溶古地貌气藏”向“相控岩性气藏”勘探的深刻转变。
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| 关 键 词： | 膏模孔 膏云岩孔隙结构 孔隙成因 岩溶储集层 |
| 收稿时间： | 2021-01-03 |
Development regularity and genetic mechanism of weathering crust reservoirs in the western Ordos Basin: take the sub-members 1-4 of Member 5 of Majiagou Formation in Tao 2 block as an example |
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| Feng Qiang-Han,Xu Shu-Mei,Chi Xin-Qi,Shu Peng-Cheng,Kong Jia-Hao,Cui Hui-Qi,Ma Hui-Lei.Development regularity and genetic mechanism of weathering crust reservoirs in the western Ordos Basin: take the sub-members 1-4 of Member 5 of Majiagou Formation in Tao 2 block as an example[J].Journal of Palaeogeography,2021,23(4):837-854. |
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| Authors: | Feng Qiang-Han Xu Shu-Mei Chi Xin-Qi Shu Peng-Cheng Kong Jia-Hao Cui Hui-Qi Ma Hui-Lei |
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| Institution: | 1.Changqing Oilfield Company,PetroChina,Xi’an 710021,China;2.Key Lab of Submarine Geosciences and Prospecting Techniques,Ministry of Education,Ocean University of China,Shandong Qingdao 266100,China;3.College of Marine Geosciences,Ocean University of China,Shandong Qingdao 266100,China;4.Frontiers Science Center for Deep Ocean Multispheres and Earth System,Shandong Qingdao 266100,China |
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| Abstract: | The top of the Majiagou Formation of the Lower Paleozoic in the Ordos Basin suffered from long-term weathering and denudation and formed a weathered crust karst reservoir dominated by gypsodolomite. The sub-members 1-4 of Member 5 of Majiagou Formation of the Tao 2 block in the western part of Ordos Basin are mainly made up of gypsodolomite interbedded with dolomite and calcite dolomite. Based on core observation,polarized microscopic analysis,and scanning electron microscopy analysis,the multi-layered gypsodolomite are identified. Through comparing the physical and chemical properties among anhydrite,dolomite and calcite,it is concluded that the main pore space of the sub-members 1-4 of Member 5 is dissolution pores of anhydrite nodules and crystals and the accompanying swelling microfracture. The pore size is self-limited,which is restricted by the size of anhydrite nodule and crystal. Gypsodolomite and anhydrite bearing tidal flat of the supratidal zone is the prerequisite material basis and environmental condition for the formation of reservoirs,and thus lead to the strata-controlled distribution of gypsodolomite gas reservoirs. Four stages of pores dissolution are identified,with fabric selective dissolution and phased filling dissolution pores of anhydrite nodule and crystal are the key processes of reservoir formation. The reservoir is a lithologic gas reservoir controlled by the karstification of anhydrite bearing dolomite. Karstification palaeogeomorphology no longer has a critical control on the reservoir distribution. The diffusive percolation corrosion of the dispersive fresh water on the gypsodolomite strata is the main reason for the lack of the large cavities. The viewpoint of “stratified and karstified sedimentary facies controlled lithologic gas re servoirs” will promote the deep transformation of reservoir forming mechanism in the Lower Paleozoic of the study area from “karstification palaeogeomorphic-controlled gas reservoirs” to “sedimentary facies controlled lithologic gas reservoirs”. |
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| Keywords: | dissolution pores of anhydrite nodule and crystal pore structure of gypsodolomite pore genetic mechanism karstification reservoir |
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