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
Feng Qiang-Han1, Xu Shu-Mei2,3,4, Chi Xin-Qi2,3, Shu Peng-Cheng2,3, Kong Jia-Hao2,3, Cui Hui-Qi2,3, Ma Hui-Lei2,3
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
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”.
Feng Qiang-Han,Xu Shu-Mei,Chi Xin-Qi et al. 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]. JOPC, 2021, 23(4): 837-854.
[1] 包洪平,杨帆,蔡郑红,王前平,武春英. 2017. 鄂尔多斯盆地奥陶系白云岩成因及白云岩储层发育特征. 天然气工业, 37(1): 32-45. [Bao H P,Yang F,Cai Z H,Wang Q P,Wu C Y.2017. Origin and reservoir characteristics of Ordovician dolostone in the Ordos Basin. Natural Gas Industry, 37(1): 32-45] [2] 杜江民,张小莉,聂万才,徐后伟,罗川又,郭岭. 2017. 苏里格地区马五5亚段储集层特征及其主控因素. 新疆石油地质, 38(1): 34-40. [Du J M,Zhang X L,Nie W C,Xu H W,Luo C Y,Guo L.2017. Study on reservoir characteristics and main controlling factors of Ma55 submember in Sulige area. Xinjiang Petroleum Geology, 38(1): 34-40] [3] 方少仙,侯方浩. 2013. 碳酸盐岩成岩作用. 见: 冯增昭(主编). 中国沉积学. 北京: 石油工业出版社,199-265. [Fang S X,Hou F H.2013. Carbonate diagenesis. In: Feng Z Z(ed). Sedimentology of China. 2013. Beijing: Petroleum Industry Press,199-265] [4] 冯增昭,鲍志东. 1999. 鄂尔多斯奥陶纪马家沟期岩相古地理. 沉积学报, 17(1): 1-8. [Feng Z Z,Bao Z D.1999. Lithofacies paleogeography of Majiagou age of Ordovician in Ordos Basin. Acta Sedimentologica Sinica, 17(1): 1-8] [5] 金强,钟建华,邹胜章,徐守余,田飞. 2017. 碳酸盐岩岩溶储层缝洞结构与充填模式. 青岛: 中国石油大学出版社,9-199. [Jin Q,Zhong J H,Zou S Z,Xu S Y,Tian F.2017. Constructions and Filling Models of Fracture-cave in Paleokarst Carbonate Reservoirs. Qing dao: China University of Petroleum Press,9-199] [6] 韩敏强. 2010. 鄂尔多斯盆地延长探区奥陶纪末古地貌与马五段储层预测. 西北大学硕士学位论文,22-35. [Han M Q.2010. The Palaeogeomorphic recovery of late Ordovician and the section of Olm5 reservoir prediction in Yanchang exploration area of Ordos Basin. Masteral dissertation of Northwest University,22-35] [7] 侯方浩,方少仙,何江,杨西燕,付锁堂,吴正,姚泾利. 2011. 鄂尔多斯盆地靖边气田区中奥陶统马家沟组五1-五4亚段古岩溶型储层分布特征及综合评价. 海相油气地质, 16(1): 1-13. [Hou F H,Fang S X,He J,Yang X Y,Fu S T,Wu Z,Yao J L.2011. Distribution characters and comprehensive evaluation of Middle Ordovician Majiagou 51-54 submembers reservoirs in Jingbian Gas Field area,Ordos Basin. Marine Oil and Gas Geology, 16(1): 1-13] [8] 黄思静,杨俊杰,张文正. 1996. 石膏对白云岩溶解影响的实验模拟研究. 沉积学报, 14(1): 103-109. [Huang S J,Yang J J,Zhang W Z.1996. Effects of gypsum(or anhydrite)on dissolution of dolomite under different temperatures and pressures of epigenesis and burial diagenesis. Acta Sedimentologica Sinica, 14(1): 103-109] [9] 雷卞军,付金华,孙粉锦,王勇,王身建. 2010. 鄂尔多斯盆地奥陶系马家沟组层序地层格架研究: 兼论陆表海沉积作用和早期成岩作用对相对海平面变化的响应. 地层学杂志, 34(2): 145-153. [Lei B J,Fu J H,Sun F J,Wang Y,Wang S J.2010. Sequence stratigraphy of Ordovician Majiagou Formation in Ordos Basin: sedimentation and early diagenesis related to eustatic sea level changes. Journal of Stratigraphy, 34(2): 145-153] [10] 李维,张军涛,朱筱敏,孙宜朴,李淑筠. 2016. 鄂尔多斯盆地富县地区马五段白云岩储层特征与演化. 岩性油气藏, 28(3): 58-67. [Li W,Zhang J T,Zhu X M,Sun Y P,Li S J.2016. Characteristics and evolution of the Ordovician dolomite reservoir of Ma 5 member in Fuxian area,Ordos Basin. Lithologic Reservoirs, 28(3): 58-67] [11] 覃小丽,李荣西,席胜利,杨涛,程敬华,赵帮胜,王宁. 2017. 鄂尔多斯盆地东部上古生界储层热液蚀变作用. 天然气地质科学, 28(1): 43-51. [Qin X L,Li R X,Xi S L,Yang T,Cheng J H,Zhao B S, Wang N.2017. Hydrothermal alternation and its influences on quality of the Upper Paleozoic gas reservoirs in the eastern Ordos Basin. Natural Gas Geoscience, 28(1): 43-51] [12] 沈扬,吴兴宁,王少依,吴东旭,丁振纯,于洲. 2018. 鄂尔多斯盆地东部奥陶系风化壳岩溶储层孔隙充填特征. 海相油气地质, 23(3): 21-32. [Shen Y,Wu X N,Wang S Y,Wu D X,Ding Z C,Yu Z.2018. Pore-filling characteristics of Ordovician karst reservoirs in eastern Ordos Basin. Marine Oil and Gas Geology, 23(3): 21-32] [13] 司马立强,黄丹,韩世峰,冯春珍,焦雨佳,宁治军. 2015. 鄂尔多斯盆地靖边气田南部古风化壳岩溶储层有效性评价. 地质勘探, 35(4): 7-14. [Sima L Q,Huang D,Han S F,Feng C Z,Jiao Y J,Ning Z J.2015. Effectiveness evaluation of palaeo-weathering crust-type karst reservoirs in the southern Jingbian Gas Field,Ordos Basin. Geology Explore, 35(4): 7-14] [14] 宋磊,宁正福,丁冠阳. 2017. 鄂尔多斯盆地苏东地区下古生界马五5亚段白云岩成因及特征. 油气地质与采收率, 24(5): 34-39. [Song L,Ning Z F,Ding G Y.2017. Genesis and characteristics of Lower Paleozoic dolomite of submember Mawu 5 in Majiagou Formation,Sudong region in Ordos Basin. Petroleum Geology and Recovery Efficiency, 24(5): 34-39] [15] 苏中堂,陈洪德,徐粉燕,金学强. 2013. 鄂尔多斯盆地马家沟组白云岩成因及其储集性能. 海相油气地质, 18(2): 15-23. [Su Z T,Chen H D,Xu F Y,Jin X Q.2013. Genesis and reservoir property of Lower Ordovician Majiagou dolostones in Ordos Basin. Marine Oil and Gas Geology, 18(2): 15-23] [16] 熊鹰,李凌,文彩霞,侯云东,肖笛,钟原,聂万才,曹剑,谭秀成. 2016. 鄂尔多斯盆地东北部奥陶系马五1+2储层特征及成因. 石油与天然气地质, 37(5): 691-701. [Xiong Y,Li L,Wen C X,Hou Y D,Xiao D,Zhong Y,Nie W C,Cao J,Tan X C.2016. Characteristics and genesis of Ordovician Ma5 1+2 sub-member reservoir in northeastern Ordos Basin. Oil and Gas Geology, 37(5): 691-701] [17] 王琪,许勇,刘新社,马东旭,马晓峰,李树同. 2016. 岩溶背景下的优质天然气储层形成机理及主控因素: 以鄂尔多斯盆地奥陶系马家沟组马五$_{4}^{1}$储层为例. 天然气地质科学, 27(12): 2103-2114. [Wang Q,Xu Y, Liu X S,Ma X D,Ma X F,Li S T.2016. Forming mechanism and main controlling factors on the high-quality gas re servoirs restricted by paleokarst background: a case from Ordovician M5 1-4 carbonate Ordos Basin. Natural Gas Geoscience, 27(12): 2103-2114] [18] 王起琮,张宇,杨奕华,杨伟利,李洁. 2018. 鄂尔多斯盆地马家沟组层序地层与岩相分布. 西北大学学报(自然科学版), 48(4): 568-577. [Wang Q C,Zhang Y,Yang Y H,Yang W L,Li J.2018. Sequence stratigraphic and lithofacies distributions of Majiagou Formation in Ordos Basin. Journal of Northwest University(Natural Science Edition), 48(4): 568-577] [19] 王国亭,程立华,孟德伟,朱玉杰,孙建伟,黄锦袖,彭艳霞. 2018. 鄂尔多斯盆地东部奥陶系古岩溶型碳酸盐岩致密储层特征、形成机理与天然气富集潜力. 石油与天然气地质, 39(4): 685-695. [Wang G T,Cheng L H,Meng D W,Zhu Y J,Sun J W,Huang J X,Peng Y X.2018. Characterization and formation of the Ordovician tight paleo-karst carbonates in the eastern Ordos Basin and its gas accumulation. Oil and Gas Geology, 39(4): 685-695] [20] 王建民,王佳媛,郭德郧,郭向东,高海仁,严云奎,聂武军,秦锐. 2013. 鄂尔多斯盆地东部奥陶系风化壳岩溶古地貌与储层特征. 北京: 石油工业出版社,1-187. [Wang J M,Wang J Y, Guo D X,Guo X D,Gao H R,Yan Y K,Nie W J,Qin R.2013. Weathering Crust Paleogeomorphology and Reservoir Characteristics of Ordovician in Eastern Ordos Basin. Beijing: Petroleum Industry Press,1-187] [21] 王玉萍,董春梅,陈洪德,苏中堂,张长俊,郝哲敏. 2014. 鄂尔多斯盆地中西部奥陶纪热液活动的证据及其对储层发育的影响. 海相油气地质, 19(2): 23-31. [Wang Y P,Dong C M,Chen H D,Su Z T,Zhang C J,Hao Z M.2014. Petrological evidence of Ordovician hydrothermal activities and its geological significance to reservoir development in central and western parts of Ordos Basin. Marine Oil and Gas Geology, 19(2): 23-31] [22] 魏丽,王震亮,冯强汉,王勇. 2015. 靖边气田北部奥陶系马五1亚段碳酸盐岩成岩作用及其孔隙结构特征. 天然气地球科学, 26(12): 2234-2244. [Wei L,Wang Z L,Feng Q H,Wang Y.2015. Diagenesis in carbonate reservoir and pore structure characte ristic from Ordovician Ma51 sub-member reservoir in the northern Jingbian Gas Field. 2015. Natural Gas Geoscience, 26(12): 2234-2244] [23] 闫志为. 2008. 硫酸根离子对方解石和白云石溶解度的影响. 中国岩溶, 27(1): 24-31. [Yan Z W.2008. Influence of $ SO_{4}^{2-}$on the solubility of calcite and dolomite. Carsologica Sinica, 27(1): 24-31] [24] 闫志为,刘辉利,张志卫. 2009. 温度及CO2对方解石和白云石溶解度影响特征分析. 中国岩溶, 28(1): 7-11. [Yan Z W,Liu H L,Zhang Z W.2009. Influence of temperature and $P_{CO_{2}}$ on the solubility of calcite and dolomite. Carsologica Sinica, 28(1): 7-11] [25] 杨华,付锁堂,马振芳,包洪平. 2004. 天环地区奥陶系白云岩储集体特征. 天然气工业, 24(9): 11-16. [Yang H,Fu S T,Ma Z F,Bao H P.2004. The reservoir characteristics of Ordovician dolomite in Tianhuan area. Natural Gas Industry, 24(9): 11-16] [26] 杨华,刘新社,张道锋. 2013. 鄂尔多斯盆地奥陶系海相碳酸盐岩天然气成藏主控因素及勘探进展. 天然气工业, 33(5): 1-12. [Yang H,Liu X S,Zhang D F.2013. Main controlling factors of gas pooling in Ordovician marine carbonate reservoirs in the Ordos Basin and advancing gas exploration. Natural Gas Industry, 33(5): 1-12] [27] 姚泾利,王兰萍,张庆,李泽敏,张加林. 2011. 鄂尔多斯盆地南部奥陶系古岩溶发育控制因素及展布. 天然气地质科学, 22(1): 56-66. [Yao J L,Wang L P,Zhang Q,Li Z M,Zhang J L.2011. Controlling factor and distribution of paleo-karst development in Ordovician of southern Ordos Basin. Natural Gas Geoscience, 22(1): 56-66] [28] 于洲,孙六一,吴兴宁,吴东旭,姚学辉,丁振纯. 2012. 鄂尔多斯盆地靖西地区马家沟组中组合储层特征及主控因素. 海相油气地质, 17(4): 49-56. [Yu Z,Sun L Y,Wu X N,Wu D X,Yao X H,Ding Z C.2012. Characteristics and controlling factors of the middle array of Ordovician Majiagou reservoirs to the West of Jingbian Gas Field,Ordos Basin. Marine Oil and Gas Geology, 17(4): 49-56] [29] 左智峰,熊鹰,何为,杨勃,任灵,文汇博,刘耘,刘灵,谭秀成. 2019. 鄂尔多斯盆地中部马五段盐下储层成岩作用与孔隙演化. 地质科技情报, 38(5): 155-164. [Zuo Z F,Xiong Y,He W,Yang B,Ren L,Wen H B,Liu Y,Liu L,Tan X C.2019. Diagenesis and porosity evolution of the subsalt Member 5 of Majiagou Formation reservoir in the central Ordos Basin. Geological Science and Technology Information, 38(5): 155-164] [30] 周进高,张帆,郭庆新. 2011. 鄂尔多斯盆地下奥陶统马家沟组障壁潟湖沉积相模式及有利储层分布规律. 沉积学报, 29(1): 64-71. [Zhou J G,Zhang F,Guo Q X.2011. Barrier-lagoon sedimentary model and reservoir distribution regularity of Lower Ordovician Majiagou Formation in Ordos Basin. Acta Sedimentologica Sinica, 29(1): 64-71] [31] Liu Z,Yuan D,Dreybrodt W.2005. Comparative study of dissolution rate-determining mechanisms of limestone and dolomite. Environmental Earth Sciences, 49(2): 274-279. [32] Xiao D,Tan X C,Zhang D F,He W,Li L,Shi Y H,Chen J P,Cao J.2019. Discovery of syngenetic and eogenetic karsts in the Middle Ordovician gypsum-bearing dolomites of the eastern Ordos Basin(central China)and their heterogeneous impact on reservoir quality. Marine and Petroleum Geology, 99: 190-207. [33] Xiong Y,Tan X C,Zuo Z F,Zou G L,Liu M J,Liu Y,Liu L,Xiao D,Zhang J.2019. Middle Ordovician multi-stage penecontemporaneous karstification in North China: implications for reservoir genesis and sea level fluctuations. Journal of Asian Earth Sciences, 183: 1-14.
