Palaeokarst characteristics and effects on reservoirs in the fourth member of Leikoupo Formation, Longmen Mountain front, western Sichuan Basin
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摘要: 川西龙门山前带雷口坡组四段主要岩石类型为潮坪相白云岩。该套白云岩储层的形成主要受沉积相带、白云化作用和溶蚀作用控制。利用岩心观察、薄片分析、激光碳氧同位素、探针微量元素、阴极发光及包裹体测温等实验手段,对溶蚀作用进行研究。研究表明该储层经历了3期溶蚀作用,即准同生期、古表生期和埋藏期,分别形成粒内溶孔及铸膜孔、膏溶孔洞以及沿裂缝或缝合线分布的溶蚀孔洞。深入研究古表生期岩溶作用和膏溶作用发现,印支Ⅰ幕大气水作用的识别标志有不规则网络状风化裂缝、岩溶及膏溶膏变角砾岩、保持石膏板状形态或直角边形态的去膏化方解石、广泛发育的膏模孔及膏溶孔洞,同时具有低的碳氧稳定同位素值、宽值域的锶同位素值、低含量的Sr-Mn-Fe-K-Na微量元素、低温单相水溶包裹体等地球化学特征,印支Ⅰ幕大气水作用下含膏白云岩内膏溶作用是储集层形成的关键作用。Abstract: Dolostones of tidal flat facies are the major reservoir rock type of the fourth member of Leikoupo Formation, Longmen Mountain front, western Sichuan Basin. The reservoir controls are dominated by phase belt, dolomitization and denudation. Core observation, cast thin section identification, laser carbon and oxygen isotopes, cathode luminescence, electron probe and inclusion thermometry were used to study the denudation effect. This reservoir went through three periods of denudation, including penecontemporaneous period, epidiagenetic period and buried period, which separately formed intragranular and moldic pores, gypsum caves, and fault-line cavities. The studies of karstification and gypsum dissolution in the paleo-epigenetic period showed that, the distinguishing signs of meteoric water impacts in episode I of the Indosinian Movement include the irregular network of weathering cracks, karst and gypsum breccia, de-anointed calcite maintaining gypsum board shape or right-angle edge shape, widely developed paste mold holes and paste-dissolved holes. These products are featured by low carbon and oxygen stable isotope values, a wide range of strontium isotope values, low content of Sr-Mn-Fe-K-Na trace elements, low-temperature single-phase water-soluble inclusions. The dissolution of gypsum in episode I of the Indosinian Movement is the key for reservoir generation.
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图 1 川西龙门山前带钻井分布和地层综合柱状图
据文献[4]修改。
Figure 1. Borehole locations and stratigraphic sequence of Longmen Mountain front, western Sichuan Basin
图 2 川西龙门山前带雷口坡组四段古表生期大气水溶蚀作用识别标志
a.浅灰色微晶白云岩,岩心表面见网络状风化裂缝,A7井,4-5/45(岩心编号表示第4回次取心45块岩心中的第5块,下文相同含义),岩心照片;b.灰色微晶白云岩,不规则裂缝,A7井,4-4/45,普通薄片,单偏光,100-;c.灰色微晶白云岩,不规则裂缝内充填白云石泥,A7井,4-4/45,阴极发光,100-;d.膏溶膏变角砾岩,呈椭圆状,A5井,8-11/83,岩心照片;e.灰色膏溶膏变角砾岩,A2井,5-4/33,普通薄片,单偏光,100-;f.灰色膏溶膏变角砾岩,不发光,A2井,5-4/33,阴极发光,100-;g.含灰白云岩,见去膏化方解石,A1井,1-56/57,普通薄片,单偏光,50-;h.含云灰岩,A4井,4-59/66,普通薄片,单偏光,100-;i.含云灰岩,不发光,A4井,4-59/66,阴极发光,100-;j.藻云岩,顺层分布的膏模孔,A2井,10-10/45,岩心照片;k.藻砂屑云岩,孤立分布的孔洞,A5井,7-13/88,岩心照片;l.藻云岩,具有直角边的膏溶孔,蓝色为灌注的铸体,代表储集空间,A2井,10-43/45,铸体薄片,100-
Figure 2. Identification of palaeokarst in fourth member of Leikoupo Formation, Longmen Mountain front, western Sichuan Basin
表 1 川西龙门山前带雷四段古岩溶产物地球化学特征
Table 1. Geochemical characteristics of palaeokarst deposits in fourth member of Leikoupo Formation, Longmen Mountain front, western Sichuan Basin
序号 井号 岩心块号 产状 δ13CPDB/‰ δ18OPDB/‰ 锶同位素87Sr/86Sr K/(μg·g-1) Na/(μg·g-1) Sr/(μg·g-1) Mn/(μg·g-1) Fe/(μg·g-1) 均一法温度/℃ 冰点/℃ 盐度/% 1 A7 2-4/22 ① 0.69 -5.67 0.707 807 60 251 2 A7 2-14/22 ② 1.18 -5.48 0.707 863 66 < 0.01 0.02 985 23 0.01 3 A2 6-12/54 ③ 0.77 -7.67 0.707 916 76 < 0.01 0.04 94.4 7 0.11 126.1 -9.0 12.9 4 A2 7-16/29 ③ -0.15 -6.77 0.34 0.48 62.8 < 5 0.27 115.1 -6.9 10.4 5 A2 9-19/49 ③ 1.59 -6.63 0.708 076 72 < 0.01 0.02 274 11 < 0.01 122.4 -9.4 13.3 6 A2 9-49/49 ③ 0.85 -7.93 0.709 386 24 0.01 0.05 256 < 5 0.02 129.1 -6.9 10.4 7 A8 2-19/44 ③ 0.97 -5.18 0.01 0.06 214 < 5 0.03 8 A5 4-15/58 ③ -0.38 -8.55 9 A5 4-28/58 ③ 0.35 -7.71 0.708 451 31 < 0.01 0.04 972 < 5 0.01 116.4 10 A5 4-56/58 ③ 0.69 -8.89 0.708 125 90 196.5 11 A5 5-25/67 ③ -1.07 -7.61 328 113.4 -10.6 14.6 12 A5 6-49/79 ③ 0.90 -9.01 < 0.01 0.08 81.9 < 0.01 123.2 13 A5 6-55/79 ③ 0.07 -8.36 < 0.01 0.04 218 < 5 0.01 14 A6 2-21/60 ③ 0.67 -7.31 0.707 789 16 130.1 15 A1 1-56/57 ③ 1.17 -6.23 16 A2 1-54/67 ④ 1.67 -7.44 17 A2 4-45/60 ④ 0.63 -7.46 0.708 392 08 < 0.01 0.03 322 < 5 0.01 18 A2 8-14/33 ④ 0.83 -7.79 0.708 569 25 < 0.01 0.02 143 5 < 0.01 19 A5 1-68/76 ④ 0.85 -8.96 < 0.01 0.05 146 < 5 0.01 114.0 20 A5 7-77/88 ④ 0.37 -7.42 0.708 293 81 478 137.2 -6.5 9.9 21 A5 8-11/83 ④ -2.30 -8.86 22 A5 8-14/83 ④ 1.23 -6.58 0.708 296 66 < 0.01 0.01 266 11 0.01 23 A2 2-22/66 ⑤ 1.46 -5.94 0.707 923 88 246 24 A2 2-35/66 ⑤ 1.11 -5.91 0.708 129 75 244 25 A7 3-1/26 ⑥ -0.26 -7.30 26 A5 2-57/73 ⑥ 1.37 -6.41 0.708 008 81 < 0.01 0.02 271 7 < 0.01 27 A5 2-57/73 ⑥ 1.40 -6.50 0.708 239 04 < 0.01 0.02 264 7 < 0.01 28 A5 2-60/73 ⑥ 1.47 -6.29 29 A6 1-37/73 ⑥ 1.86 -5.00 0.708 171 04 < 0.01 0.03 262 11 < 0.01 30 A8 6-30/75 ⑦ 1.74 -2.73 0.707 923 77 3 050 注:“产状描述”中,①指代微晶灰岩;②指代亮晶砂屑灰岩;③指代去膏化方解石;④指代膏溶孔洞方解石;⑤指代印支期Ⅰ幕的低角度裂缝方解石;⑥指代构造裂缝纤柱状方解石(印支期Ⅰ幕);⑦指代受热液改造的高角度裂缝纤柱状—粒状方解石。 -
[1] [1]李勇, 段永明, 赵爽, 等. 川西坳陷彭州地区雷四上亚段白云岩形成机理[J]. 沉积与特提斯地质, 2017, 37(3): 13-21. https://www.cnki.com.cn/Article/CJFDTOTAL-TTSD201703002.htmLI Yong, DUAN Yongming, ZHAO Shuang, et al. Genetic mechanism of the dolostones from the upper part of the fourth member of the Leikoupo Formation in the Pengzhou region, Western Sichuan Depression[J]. Sedimentary Geology and Tethyan Geology, 2017, 37(3): 13-21. https://www.cnki.com.cn/Article/CJFDTOTAL-TTSD201703002.htm [2] 李书兵, 许国明, 宋晓波. 川西龙门山前构造带彭州雷口坡组大型气田的形成条件[J]. 中国石油勘探, 2016, 21(3): 74-82. https://www.cnki.com.cn/Article/CJFDTOTAL-KTSY201603007.htmLI Shubing, XU Guoming, SONG Xiaobo. Forming conditions of Pengzhou large gas field of Leikoupo Formation in Longmenshan piedmont tectonic belt, western Sichuan Basin[J]. China Petroleum Exploration, 2016, 21(3): 74-82. https://www.cnki.com.cn/Article/CJFDTOTAL-KTSY201603007.htm [3] 许国明, 宋晓波, 冯霞, 等. 川西地区中三叠统雷口坡组天然气勘探潜力[J]. 天然气工业, 2013, 33(8): 8-14. https://www.cnki.com.cn/Article/CJFDTOTAL-TRQG201308003.htmXU Guoming, SONG Xiaobo, FENG Xia, et al. Gas potential of the Middle Triassic Leikoupo Fm in the western Sichuan Basin[J]. Natural Gas Industry, 2013, 33(8): 8-14. https://www.cnki.com.cn/Article/CJFDTOTAL-TRQG201308003.htm [4] 王琼仙, 宋晓波, 陈洪德, 等. 川西龙门山前雷口坡组四段白云岩储层胶结物对早期孔隙的影响[J]. 石油实验地质, 2018, 40(6): 757-763. doi: 10.11781/sysydz201806757WANG Qiongxian, SONG Xiaobo, CHEN Hongde, et al. Cement characteristics and effects on dolomite reservoir pores in the fourth member of Leikoupo Formation, Longmen Mountain front, western Sichuan Basin[J]. Petroleum Geology & Experiment, 2018, 40(6): 757-763. doi: 10.11781/sysydz201806757 [5] 陈昱林, 曾焱, 段永明, 等. 川西龙门山前雷口坡组四段白云岩储层孔隙结构特征及储层分类[J]. 石油实验地质, 2018, 40(5): 621-631. doi: 10.11781/sysydz201805621CHEN Yulin, ZENG Yan, DUAN Yongming, et al. Pore structure characteristics and reservoir classification of dolomite reservoirs in fourth member of Leikoupo Formation, Longmen Mountain front, western Sichuan Basin[J]. Petroleum Geology & Experiment, 2018, 40(5): 621-631. doi: 10.11781/sysydz201805621 [6] 李凌, 谭秀成, 周素彦, 等. 四川盆地雷口坡组层序岩相古地理[J]. 西南石油大学学报(自然科学版), 2012, 34(4): 13-22. https://www.cnki.com.cn/Article/CJFDTOTAL-XNSY201204003.htmLI Ling, TAN Xiucheng, ZHOU Suyan, et al. Sequence lithofacies paleography of Leikoupo Formation, Sichuan Basin[J]. Journal of Southwest Petroleum University (Science & Techno-logy Edition), 2012, 34(4): 13-22. https://www.cnki.com.cn/Article/CJFDTOTAL-XNSY201204003.htm [7] 唐宇. 川西地区雷口坡组沉积与其顶部风化壳储层特征[J]. 石油与天然气地质, 2013, 34(1): 42-47. https://www.cnki.com.cn/Article/CJFDTOTAL-SYYT201301008.htmTANG Yu. Characterization of the sedimentation of the Leikoupo Formation and the weathering crust reservoirs at the top of the formation in the western Sichuan Basin[J]. Oil & Gas Geology, 2013, 34(1): 42-47. https://www.cnki.com.cn/Article/CJFDTOTAL-SYYT201301008.htm [8] ALKATTAN M, OELKERS E H, DANDURAND J L, et al. An experimental study of calcite and limestone dissolution rates as a function of pH from 1 to 3 and temperature from 25 to 80℃[J]. Chemical Geology, 1998, 151(1/4): 199-214. [9] HUERTAS F J, CABALLERO E, DE CISNEROS C J, et al. Kinetics of montmorillonite dissolution in granitic solutions[J]. Applied Geochemistry, 2001, 16(4): 397-407. [10] 朱彤. 四川盆地陆相页岩油气富集主控因素及类型[J]. 石油实验地质, 2020, 42(3): 345-354. doi: 10.11781/sysydz202003345ZHU Tong. Main controlling factors and types of continental shale oil and gas enrichment in Sichuan Basin[J]. Petroleum Geology & Experiment, 2020, 42(3): 345-354. doi: 10.11781/sysydz202003345 [11] 李宏涛, 胡向阳, 史云清, 等. 四川盆地川西坳陷龙门山前雷口坡组四段气藏层序划分及储层发育控制因素[J]. 石油与天然气地质, 2017, 38(4): 753-763. https://www.cnki.com.cn/Article/CJFDTOTAL-SYYT201704012.htmLI Hongtao, HU Xiangyang, SHI yunqing, et al. Sequence division and controlling factors of reservoir development of the 4th Member of Leikoupo Formation in foreland of Longmen Mountains in the Western Sichuan Depression, Sichuan Basin[J]. Oil & Gas Geo-logy, 2017, 38(4): 753-763. https://www.cnki.com.cn/Article/CJFDTOTAL-SYYT201704012.htm [12] 宋晓波, 王琼仙, 隆轲, 等. 川西地区中三叠统雷口坡组古岩溶储层特征及发育主控因素[J]. 海相油气地质, 2013, 18(2): 8-14. https://www.cnki.com.cn/Article/CJFDTOTAL-HXYQ201302004.htmSONG Xiaobo, WANG Qiongxian, LONG Ke, et al. Characteristics and main controlling factors of Middle Triassic Leikoupo paleokarst reservoirs in western Sichuan Basin[J]. Marine Origin Petroleum Geology, 2013, 18(2): 8-14. https://www.cnki.com.cn/Article/CJFDTOTAL-HXYQ201302004.htm [13] 李素华, 卢齐军, 许国明, 等. 川西XC地区雷口坡组顶不整合面储层预测方法[J]. 石油地球物理勘探, 2013, 48(5): 793-798. https://www.cnki.com.cn/Article/CJFDTOTAL-SYDQ201305020.htmLI Suhua, LU Qijun, XU Guoming, et al. Reservoir prediction in the top Leikoupo unconformity surface in the area XC, Sichuan[J]. Oil Geophysical Prospecting, 2013, 48(5): 793-798. https://www.cnki.com.cn/Article/CJFDTOTAL-SYDQ201305020.htm [14] 谢刚平. 川西坳陷雷四上亚段晶粒白云岩成岩作用和孔隙演化[J]. 长江大学学报(自然科学版), 2015, 12(17): 24-26. https://www.cnki.com.cn/Article/CJFDTOTAL-CJDL201517005.htmXIE Gangping. Diagenesis and porosity evolution of crystal grain dolomite in the upper section of the 4th member of Leikoupo Formation in the Western Sichuan Depression[J]. Journal of Yangtze University (Natural Science Edition), 2015, 12(17): 24-26. https://www.cnki.com.cn/Article/CJFDTOTAL-CJDL201517005.htm [15] 马治鸾, 陈洪德, 钟怡江, 等. 四川盆地东北部元坝地区中三叠统雷口坡组四段古岩溶特征及其油气地质意义[J]. 地质通报, 2012, 31(4): 577-585. https://www.cnki.com.cn/Article/CJFDTOTAL-ZQYD201204010.htmMA Zhiluan, CHEN Hongde, ZHONG Yijiang, et al. Paleokarstification in carbonates of 4th member of Middle Triassic Leikoupo Formation in northeastern Sichuan Basin and its petroleum geological significance[J]. Geological Bulletin of China, 2012, 31(4): 577-585. https://www.cnki.com.cn/Article/CJFDTOTAL-ZQYD201204010.htm [16] 夏勇, 刘海锋, 袁继明, 等. 靖边气田南部古岩溶特征及有利储层发育[J]. 东北石油大学学报, 2013, 37(6): 25-31. https://www.cnki.com.cn/Article/CJFDTOTAL-DQSY201306005.htmXIA Yong, LIU Haifeng, YUAN Jiming, et al. Paleokarst characteristics and the favorable reservoirs development in southern Jingbian gas field[J]. Journal of Northeast Petroleum University, 2013, 37(6): 25-31. https://www.cnki.com.cn/Article/CJFDTOTAL-DQSY201306005.htm -