Reservoir characteristics and genesis of shale oil "sweet spots" in Lucaogou Formation, Jimsar Sag, Junggar Basin
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摘要: 准噶尔盆地吉木萨尔凹陷芦草沟组页岩油层系岩性复杂,非均质性强,“甜点体”形成规律是制约地质理论研究和勘探开发的一个关键难题。通过岩心观察、薄片鉴定和含油性分析,针对“甜点体”地质特征进行了表征,分析了影响产能的地质因素,确定了可动油孔隙的形成机理。吉木萨尔凹陷芦草沟组“甜点体”的岩性主要为岩屑长石粉细砂岩、云屑砂岩和砂屑云岩,孔隙度为5.75%~11.9%,渗透率为(0.02~1.26)×10-3 μm2,其中岩屑长石粉细砂岩的孔喉贡献率最大,“甜点体”的储集空间为溶蚀粒间(内)孔、裂缝;页岩油产能的大小受控于可动油孔隙的分布以及岩石组分中泥质、石英质和白云质的含量,可动油孔隙是在同生—准同生淋滤作用和酸性流体埋藏溶蚀联合作用下形成的,层理缝沟通溶孔是控制渗透率大小的关键因素。储层成岩过程中储集空间耦合生排烃作用最终形成“甜点体”,其形成的沉积环境为受波浪作用较强的云坪、混合坪、滨湖滩砂和碳酸盐岩浅滩沉积。该发现可对同成因类型页岩油的勘探和开发提供指导。Abstract: The shale oil layers of the Lucaogou Formation in the Jimsar Sag of Junggar Basin have complex lithology and strong heterogeneity. The formation of "sweet spots" is a key problem restricting exploration and development. Through core observation, thin section analysis and oil-bearing capacity analysis, the geological features of the "sweet spots" were characterized, the geological factors affecting productivity were analyzed, and the formation mechanism of movable oil pores was determined. The lithology of "sweet spots" of the Lucaogou Formation in the Jimsar Sag is mainly lithic feldspar fine sandstone, dolomitic sandstone and gypsum dolomite, with a porosity of 5.75%-11.9% and a permeability of (0.02-1.26)×10-3 μm2, of which the lithic feldspar fine sandstone made the largest contribution to pore throats. Intergranular (intragranular) pores and fractures provide storage space for "sweet spots". Shale oil yield is controlled by the pore distribution for movable oil and the contents of argillaceous, quartz and dolomite. The movable oil pores are formed under the combined action of syngenetic and quasi-syngenetic leaching and acid fluid burial dissolution. The key factor to control permeability is the connection of dissolved pores by bedding cracks. In the process of reservoir diagenesis, the coupling of hydrocarbon generation and expulsion in the reservoir space will eventually form a "sweet spot", mainly in environments such as dolomitic flat, mixed flat, lakeside beach sand and carbonate shoal which are strongly influenced by waves. This discovery can provide guidance for the exploration and development of shale oil of the same genetic type.
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Key words:
- movable oil pores /
- dissolution /
- sweet spots /
- shale oil /
- Lucaogou Formation /
- Jimsar Sag /
- Junggar Basin
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图 5 准噶尔盆地吉木萨尔凹陷芦草沟组页岩油“甜点体”孔隙空间特征
a.吉174井(3275.2 m),“甜点体”上部,白云质粉砂岩,扫描电镜图像,粒间溶孔发育,孔径多小于10 μm;b.吉174井(3 152.6 m),“甜点体”下部,白云质粉砂岩,扫描电镜图像,粒间/粒内溶孔发育,粒内溶孔较小,孔径多小于10 μm;c.吉174井(3 279.8 m),泥晶白云岩,正交偏光,层理缝发育
Figure 5. Pore space characteristics of "sweet spots" of shale oil in Lucaogou Formation, Jimsar Sag, Junggar Basin
图 10 准噶尔盆地吉木萨尔凹陷芦草沟组页岩溶蚀孔隙、裂缝与含油性关系
a.泥晶灰质云岩,受表生淋滤作用影响,同生、准同生云化作用形成的泥晶白云岩,沿微裂缝及其周围发生去云化作用,并发生溶蚀作用,形成少量溶蚀孔,吉23井2 320.08 m岩石薄片(-)混合液染色;b.钠长石化及钠长石充填作用,有机酸作用形成的溶蚀孔被自生钠长石半充填, 发育钠长石晶间孔,钠长石对部分泥质及粉砂具交代作用,吉174井,3 121.1 m,含泥质云质粉砂岩(+)岩石薄片;c.溶蚀孔隙发育,层理缝沟通溶孔,进一步增加裂缝强度,顺层理缝含油饱和度高
Figure 10. Dissolved pores and cracks vs. oil-bearing capacity of shale in Lucaogou Formation, Jimsar Sag, Junggar Basin
表 1 准噶尔盆地吉木萨尔凹陷芦草沟组页岩油“甜点体”各类岩石孔隙度和渗透率统计
Table 1. Porosity and permeability of various rocks of "sweet spots" of shale oil in Lucaogou Formation, Jimsar Sag, Junggar Basin
参数 岩屑长石粉细砂岩 泥质粉砂岩 云屑砂岩 粉砂质泥岩 泥岩 云质泥岩 砂屑云岩 粉砂质云岩 泥质云岩 白云岩 平均孔隙度/% 11.90 7.36 10.08 7.18 5.75 6.42 9.67 7.35 5.89 7.89 平均渗透率/10-3 μm2 0.51 0.04 0.12 0.06 0.06 0.02 0.42 0.60 0.09 1.26 表 2 准噶尔盆地吉木萨尔凹陷芦草沟组页岩油“甜点体”优势岩性不同孔喉半径的孔隙贡献
Table 2. Pore contribution of different pore throat radius of dominant lithology of "sweet spots" of shale oil in Lucaogou Formation, Jimsar Sag, Junggar Basin
% 岩性 不同孔喉半径孔隙的占比和对产能的贡献 >300 nm 100~300 nm 50~100 nm < 50 nm 占比 贡献 占比 贡献 占比 贡献 占比 贡献 岩屑长石粉细砂岩 20 90 22 9 20 1 38 0 云屑砂岩 25 76 17 18 18 6 40 0 砂屑云岩 10 95 11 4 19 1 60 0 -
[1] 赵文智, 胡素云, 侯连华, 等. 中国陆相页岩油类型、资源潜力及与致密油的边界[J]. 石油勘探与开发, 2020, 47(1): 1-10. https://www.cnki.com.cn/Article/CJFDTOTAL-SKYK202001002.htmZHAO Wenzhi, HU Suyun, HOU Lianhua, et al. Types and resource potential of continental shale oil in China and its boundary with tight oil[J]. Petroleum Exploration and Development, 2020, 47(1): 1-10. https://www.cnki.com.cn/Article/CJFDTOTAL-SKYK202001002.htm [2] 王小军, 杨智峰, 郭旭光, 等. 准噶尔盆地吉木萨尔凹陷页岩油勘探实践与展望[J]. 新疆石油地质, 2019, 40(4): 402-413. https://www.cnki.com.cn/Article/CJFDTOTAL-XJSD201904003.htmWANG Xiaojun, YANG Zhifeng, GUO Xuguang, et al. Practices and prospects of shale oil exploration in Jimsar Sag of Junggar Basin[J]. Xinjiang Petroleum Geology, 2019, 40(4): 402-413. https://www.cnki.com.cn/Article/CJFDTOTAL-XJSD201904003.htm [3] 邵雨, 杨勇强, 万敏, 等. 吉木萨尔凹陷二叠系芦草沟组沉积特征及沉积相演化[J]. 新疆石油地质, 2015, 36(6): 635-641. https://www.cnki.com.cn/Article/CJFDTOTAL-XJSD201506003.htmSHAO Yu, YANG Yongqiang, WAN Min, et al. Sedimentary characteristic and facies evolution of Permian Lucaogou Formation in Jimsar Sag, Junggar Basin[J]. Xinjiang Petroleum Geo-logy, 2015, 36(6): 635-641. https://www.cnki.com.cn/Article/CJFDTOTAL-XJSD201506003.htm [4] BAI Hua, PANG Xiongqi, KUANG Lichun, et al. Hydrocarbon expulsion potential of source rocks and its influence on the distribution of lacustrine tight oil reservoir, Middle Permian Lucaogou Formation, Jimsar Sag, Junggar Basin, Northwest China[J]. Journal of Petroleum Science and Engineering, 2017, 149: 740-755. doi: 10.1016/j.petrol.2016.09.053 [5] GAO Gang, ZHANG Weiwei, XIANG Baoli, et al. Geochemistry characteristics and hydrocarbon-generating potential of lacustrine source rock in Lucaogou Formation of the Jimusaer Sag, Junggar Basin[J]. Journal of Petroleum Science and Engineering, 2016, 145: 168-182. doi: 10.1016/j.petrol.2016.03.023 [6] CAO Zhe, LIU Guangdi, ZHAN Hongbin, et al. Geological control factors of micro oil distribution in tight reservoirs[J]. Marine and Petroleum Geology, 2016, 77: 1193-1205. doi: 10.1016/j.marpetgeo.2016.08.013 [7] HU Tao, PANG Xiongqi, WANG Xulong, et al. Source rock characteristics of Permian Lucaogou Formation in the Jimusar Sag, Junggar Basin, northwest China, and its significance on tight oil source and occurrence[J]. Geological Journal, 2017, 52(4): 624-645. doi: 10.1002/gj.2818 [8] JIANG Yiqin, LIU Yiqun, YANG Zhao, et al. Characteristics and origin of tuff-type tight oil in Jimusaer Sag, Junggar Basin, NW China[J]. Petroleum Exploration and Development, 2015, 42(6): 810-818. doi: 10.1016/S1876-3804(15)30077-X [9] 杨智, 侯连华, 林森虎, 等. 吉木萨尔凹陷芦草沟组致密油、页岩油地质特征与勘探潜力[J]. 中国石油勘探, 2018, 23(4): 76-85. https://www.cnki.com.cn/Article/CJFDTOTAL-KTSY201804010.htmYANG Zhi, HOU Lianhua, LIN Senhu, et al. Geologic characte-ristics and exploration potential of tight oil and shale oil in Lucaogou Formation in Jimsar Sag[J]. China Petroleum Exploration, 2018, 23(4): 76-85. https://www.cnki.com.cn/Article/CJFDTOTAL-KTSY201804010.htm [10] 支东明, 唐勇, 杨智峰, 等. 准噶尔盆地吉木萨尔凹陷陆相页岩油地质特征与聚集机理[J]. 石油与天然气地质, 2019, 40(3): 524-534. https://www.cnki.com.cn/Article/CJFDTOTAL-SYYT201903009.htmZHI Dongming, TANG Yong, YANG Zhifeng, et al. Geological characteristics and accumulation mechanism of continental shale oil in Jimusaer Sag, Junggar Basin[J]. Oil & Gas Geology, 2019, 40(3): 524-534. https://www.cnki.com.cn/Article/CJFDTOTAL-SYYT201903009.htm [11] 田伟, 刘慧卿, 何顺利, 等. 吉木萨尔凹陷芦草沟组致密油储层岩石微观孔隙结构表征[J]. 油气地质与采收率, 2019, 26(4): 24-32. https://www.cnki.com.cn/Article/CJFDTOTAL-YQCS201904005.htmTIAN Wei, LIU Huiqing, HE Shunli, et al. Characterization of microscopic pore structure of tight oil reservoirs in Lucaogou Formation, Jimusaer Sag[J]. Petroleum Geology and Recovery Efficiency, 2019, 26(4): 24-32. https://www.cnki.com.cn/Article/CJFDTOTAL-YQCS201904005.htm [12] 曲长胜, 邱隆伟, 操应长, 等. 吉木萨尔凹陷二叠系芦草沟组烃源岩有机岩石学特征及其赋存状态[J]. 中国石油大学学报(自然科学版), 2017, 41(2): 30-38. https://www.cnki.com.cn/Article/CJFDTOTAL-SYDX201702004.htmQU Changsheng, QIU Longwei, CAO Yingchang, et al. Organic petrology characteristics and occurrence of source rocks in Permian Lucaogou Formation, Jimsar Sag[J]. Journal of China University of Petroleum, 2017, 41(2): 30-38. https://www.cnki.com.cn/Article/CJFDTOTAL-SYDX201702004.htm [13] 葸克来, 操应长, 朱如凯, 等. 吉木萨尔凹陷二叠系芦草沟组致密油储层岩石类型及特征[J]. 石油学报, 2015, 36(12): 1495-1507. https://www.cnki.com.cn/Article/CJFDTOTAL-SYXB201512005.htmXI Kelai, CAO Yingchang, ZHU Rukai, et al. Rock types and characteristics of tight oil reservoir in Permian Lucaogou Formation, Jimsar Sag[J]. Acta Petrolei Sinica, 2015, 36(12): 1495-1507. https://www.cnki.com.cn/Article/CJFDTOTAL-SYXB201512005.htm [14] 郭旭光, 何文军, 杨森, 等. 准噶尔盆地页岩油"甜点区"评价与关键技术应用: 以吉木萨尔凹陷二叠系芦草沟组为例[J]. 天然气地球科学, 2019, 30(8): 1168-1179. https://www.cnki.com.cn/Article/CJFDTOTAL-TDKX201908010.htmGUO Xuguang, HE Wenjun, YANG Sen, et al. Evaluation and application of key technologies of "sweet area" of shale oil in Junggar Basin: case study of Permian Lucaogou Formation in Jimusar Depression[J]. Natural Gas Geoscience, 2019, 30(8): 1168-1179. https://www.cnki.com.cn/Article/CJFDTOTAL-TDKX201908010.htm [15] 张少敏, 操应长, 朱如凯, 等. 湖相细粒混合沉积岩岩石类型划分: 以准噶尔盆地吉木萨尔凹陷二叠系芦草沟组为例[J]. 地学前缘, 2018, 25(4): 198-209. https://www.cnki.com.cn/Article/CJFDTOTAL-DXQY201804020.htmZHANG Shaomin, CAO Yingchang, ZHU Rukai, et al. Lithofacies classification of fine-grained mixed sedimentary rocks in the Permian Lucaogou Formation, Jimusar Sag, Junggar Basin[J]. Earth Science Frontiers, 2018, 25(4): 198-209. https://www.cnki.com.cn/Article/CJFDTOTAL-DXQY201804020.htm [16] 靳军, 杨召, 依力哈木·尔西丁, 等. 准噶尔盆地吉木萨尔凹陷致密油储层纳米孔隙特征及其含油性[J]. 地球科学, 2018, 43(5): 1594-1601. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX201805021.htmJIN Jun, YANG Zhao, YILIHAMU E, et al. Nanopore characte-ristics and oil-bearing properties of tight oil reservoirs in Jimsar Sag, Junggar Basin[J]. Earth Science, 2018, 43(5): 1594-1601. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX201805021.htm [17] 闫林, 冉启全, 高阳, 等. 新疆芦草沟组致密油赋存形式及可动用性评价[J]. 油气藏评价与开发, 2017, 7(6): 20-25. https://www.cnki.com.cn/Article/CJFDTOTAL-KTDQ201706004.htmYAN Lin, RAN Qiquan, GAO Yang, et al. Tight oil occurrence form and recoverability evaluation of tight oil reservoir in Lucaogou Formation of Xinjiang[J]. Reservoir Evaluation and Development, 2017, 7(6): 20-25. https://www.cnki.com.cn/Article/CJFDTOTAL-KTDQ201706004.htm [18] 胡英杰. 湖相碳酸盐岩致密油主控因素及"甜点"刻画[J]. 特种油气藏, 2018, 25(6): 6-11. https://www.cnki.com.cn/Article/CJFDTOTAL-TZCZ201806002.htmHU Yingjie. Main-controlling factors and "sweet-spot" characte-rization of lacustrine carbonate tight oil reservoir[J]. Special Oil & Gas Reservoirs, 2018, 25(6): 6-11. https://www.cnki.com.cn/Article/CJFDTOTAL-TZCZ201806002.htm [19] 孟祥振, 刘聃, 孟旺才, 等. 鄂尔多斯盆地西南部延长组长7段致密油地质"甜点"评价[J]. 特种油气藏, 2018, 25(6): 90-95. https://www.cnki.com.cn/Article/CJFDTOTAL-TZCZ201806016.htmMENG Xiangzhen, LIU Dan, MENG Wangcai, et al. Geological "sweet-spot" evaluation of Chang-7 Member tight oil in the Yanchang Formation of southwestern Ordos Basin[J]. Special Oil & Gas Reservoirs, 2018, 25(6): 90-95. https://www.cnki.com.cn/Article/CJFDTOTAL-TZCZ201806016.htm [20] 许琳, 常秋生, 杨成克, 等. 吉木萨尔凹陷二叠系芦草沟组页岩油储层特征及含油性[J]. 石油与天然气地质, 2019, 40(3): 535-549. https://www.cnki.com.cn/Article/CJFDTOTAL-SYYT201903010.htmXU Lin, CHANG Qiusheng, YANG Chengke, et al. Characteristics and oil-bearing capability of shale oil reservoir in the Permian Lucaogou Formation, Jimusaer Sag[J]. Oil & Gas Geology, 2019, 40(3): 535-549. https://www.cnki.com.cn/Article/CJFDTOTAL-SYYT201903010.htm [21] 赵海玲, 王成, 刘振文, 等. 火山岩储层斜长石选择性溶蚀的岩石学特征和热力学条件[J]. 地质通报, 2009, 28(4): 412-419. https://www.cnki.com.cn/Article/CJFDTOTAL-ZQYD200904004.htmZHAO Hailing, WANG Cheng, LIU Zhenwen, et al. Characteristics of petrology and thermodynamics of selective dissolution of plagioclase in volcanic reservoir rocks[J]. Geological Bulletin of China, 2009, 28(4): 412-419. https://www.cnki.com.cn/Article/CJFDTOTAL-ZQYD200904004.htm [22] 向廷生, 蔡春芳, 付华娥. 不同温度、羧酸溶液中长石溶解模拟实验[J]. 沉积学报, 2004, 22(4): 597-602. https://www.cnki.com.cn/Article/CJFDTOTAL-CJXB200404006.htmXIANG Tingsheng, CAI Chunfang, FU Huae. Dissolution of microcline by carboxylic acids at different temperatures and complexing reaction of Al anion with carboxylic acid in aqueous solution[J]. Acta Sedimentologica Sinica, 2004, 22(4): 597-602. https://www.cnki.com.cn/Article/CJFDTOTAL-CJXB200404006.htm [23] 张云钊, 曾联波, 罗群, 等. 准噶尔盆地吉木萨尔凹陷芦草沟组致密储层裂缝特征和成因机制[J]. 天然气地球科学, 2018, 29(2): 211-225. https://www.cnki.com.cn/Article/CJFDTOTAL-TDKX201802007.htmZHANG Yunzhao, ZENG Lianbo, LUO Qun, et al. Research on the types and genetic mechanisms of tight reservoir in the Lucaogou Formation in Jimusar Sag, Junggar Basin[J]. Natural Gas Geo-science, 2018, 29(2): 211-225. https://www.cnki.com.cn/Article/CJFDTOTAL-TDKX201802007.htm [24] 马东正, 张成君, 陶辉飞, 等. 吉木萨尔凹陷芦草沟组沉积环境与物源分析[J]. 科学技术与工程, 2018, 18(23): 26-35. https://www.cnki.com.cn/Article/CJFDTOTAL-KXJS201823005.htmMA Dongzheng, ZHANG Chengjun, TAO Huifei, et al. The sedimentary environment and provenance analysis of the Lucaogou Formation in the Jimsar Sag[J]. Science Technology and Engineering, 2018, 18(23): 26-35. https://www.cnki.com.cn/Article/CJFDTOTAL-KXJS201823005.htm