Microscopic pore and fracture evolution characteristics and influencing factors during imbibition process of shale reservoirs: a case study of the first section of the first member of Longmaxi Formation, western Chongqing area, Sichuan Basin
-
摘要: 水力压裂已成为页岩气开采的重要手段，明确渗吸过程页岩储层孔隙、微裂缝的演变特征与影响因素，对指导页岩气井压后增产措施优化具有重要意义。为此，选取四川盆地渝西地区大足区块主力产层龙马溪组龙一1亚段底部黑色页岩为研究对象，开展渗吸水过程的氩离子抛光场发射扫描电镜(FE-SEM)定点观察实验，明确了渗吸水不同时间页岩储层微观孔缝演变规律。研究表明：①页岩储层渗吸水7 d后，有机质边缘有机孔出现不同程度的减小，而内部孔隙形态、大小基本不变；②粒内溶蚀孔和粒间孔会出现明显的扩溶现象，引起矿物颗粒溶蚀、脱落，增大页岩气泄气面积；③页岩储层渗吸水后不会大量萌生新的微裂缝，仅在原有微裂缝的基础上进行扩展，在吸水14 d后缝宽扩展为原来的5~10倍；④页岩储层面孔率在渗吸水后7 d达到最大值，大于7 d后微裂缝缝宽受黏土矿物持续膨胀影响出现不同程度的减小；⑤页岩储层增孔扩缝强度主要受矿物组成与孔渗性质影响，不稳定矿物与脆性矿物含量越高、粒径越大，增孔现象越明显，越有利于压后页岩气的渗流。Abstract: Hydraulic fracturing has become an important means for shale gas exploration. Understanding the evolution characteristics and influencing factors of pores and micro-fractures during the imbibition process in shale reservoirs is crucial for optimizing post-fracturing production enhancement measures. This study focuses on the black shale at the base of the first section of the first member of the Longmaxi Formation (Long 1-1 sub-member), the main production layer in the Dazu area, western Chongqing area of the Sichuan Basin. Argon ion polishing and field-emission scanning electron microscopy (FE-SEM) experiments were conducted at fixed sites to observe the evolution pattern of microscopic pores and fractures in shale reservoirs at various stages of water imbibition process. The findings revealed: (1) After water imbibition for 7 days, organic pores at the edges of organic matter exhibited varying degrees of reduction, while the internal pore shapes and sizes remained largely unchanged. (2) Intragranular dissolution pores and intergranular pores exhibited noticeable dissolution effects, resulting in mineral particle dissolution and detachment, which increased the leakage area for shale gas. (3) The water imbibition did not induce a significant amount of new micro-fractures. Instead, it extended existing micro-fractures, with the fracture width expanding by 5 to 10 times after imbibition for 14 days. (4) The surface porosity of the shale reservoir reached its peak value at day 7 of water imbibition. After 7 days, due to the continuous swelling of clay minerals, micro-fracture widths experienced varying degrees of reduction. (5) The intensity of pore and fracture expansion in shale reservoirs was primarily affected by mineral composition and pore permeability properties. Higher contents of unstable minerals and brittle minerals with larger particle sizes led to more pronounced pore expansion effects, which were conducive to post-fracturing shale gas seepage.
-
图 1 四川盆地构造区划分及研究区地理位置(a)与典型井五峰组—龙马溪组龙一1亚段地层柱状图(b)
Figure 1. Tectonic division of Sichuan Basin and geographic location of study area (a) and stratigraphic histogram from Wufeng Formation to Long 1-1 sub-member in a typical well (b)
图 2 四川盆地渝西地区龙一1亚段页岩样品面孔率计算过程
a.Z203H2-1号样品渗吸7 d后电镜下孔隙分布；b.软件识别后红色部分代表孔隙；c.对识别后的色块排序，统计孔径及面积(统计色块近似标准圆直径作为孔径)。
Figure 2. Calculation process of surface porosity for shale samples from Long 1-1 sub-member in western Chongqing area, Sichuan Basin
图 3 四川盆地渝西地区龙一1亚段页岩样品原始状态(自发吸水前)孔缝特征
a-d.Z203-1号样品有机孔(a)、无机孔(b-c)、微裂缝(d)特征；e-h.Z207-1号样品有机孔(e)、无机孔(f-g)、微裂缝(h)特征；i-l.Z203H2-1号样品有机孔(i)、无机孔(j)、微裂缝(k-l)特征；m-p.Z208-1号样品有机孔(m-n)、无机孔(o)、微裂缝(p)特征。
Figure 3. Pore and fracture characteristics of shale samples in their original state (before spontaneous water imbibition) from Long 1-1 sub-member in western Chongqing area, Sichuan Basin
图 4 四川盆地渝西地区龙一1亚段页岩样品自发吸水不同时间有机孔隙演变特征
a.Z203-1号样品自发吸水前有机质特征；b.Z203-1号样品自发吸水1 d后有机孔特征；c.Z203-1号样品自发吸水14 d后有机孔特征；d.Z208-1号样品自发吸水前有机质特征；e.Z208-1号样品自发吸水1 d后有机孔特征；f.Z208-1号样品自发吸水14 d后有机孔特征。
Figure 4. Evolution characteristics of organic pores at different times of spontaneous water imbibition for shale samples from Long 1-1 sub-member in western Chongqing area, Sichuan Basin
图 5 四川盆地渝西地区龙一1亚段Z203-1号样品自发吸水不同时间粒内溶蚀孔隙演变特征
a.自发吸水前矿物分布特征；b.自发吸水前粒内溶蚀孔特征；c.自发吸水1 d后粒内溶蚀孔特征；d.自发吸水3 d后粒内溶蚀孔特征；e.自发吸水7 d后粒内溶蚀孔特征；f.自发吸水14 d后粒内溶蚀孔特征。
Figure 5. Evolution characteristics of intragranular dissolution pores at different times of spontaneous water imbibition for sample Z203-1 from Long 1-1 sub-member in western Chongqing area, Sichuan Basin
图 6 四川盆地渝西地区龙一1亚段Z203-1号样品自发吸水不同时间矿物粒间孔隙演变特征
a.自发吸水前矿物分布特征；b.自发吸水前矿物粒间孔隙特征；c.自发吸水1 d后矿物粒间孔隙特征；d.自发吸水3 d后矿物粒间孔隙特征；e.自发吸水7 d后矿物粒间孔隙特征；f.自发吸水14 d后矿物粒间孔隙特征。
Figure 6. Evolution characteristics of intergranular pores of minerals at different times of spontaneous water imbibition for sample Z203-1 from Long 1-1 sub-member in western Chongqing area, Sichuan Basin
图 7 四川盆地渝西地区龙一1亚段Z208-1号样品自发吸水不同时间基质矿物间微裂缝演变特征
a.自发吸水前矿物分布及微裂缝位置；b.自发吸水前微裂缝特征；c.自发吸水1 d后微裂缝特征；d.自发吸水3 d后微裂缝特征；e.自发吸水7 d后微裂缝特征；f.自发吸水14 d后微裂缝特征。
Figure 7. Evolution characteristics of micro-fractures between matrix minerals at different times of spontaneous water imbibition for sample Z208-1 from Long 1-1 sub-member in western Chongqing area, Sichuan Basin
图 8 四川盆地渝西地区龙一1亚段Z207-1号样品自发吸水不同时间黏土矿物—有机质微裂缝演变特征
a.自发吸水前微裂缝及矿物分布特征；b.自发吸水前微裂缝发育特征；c.自发吸水1 d后微裂缝特征；d.自发吸水3 d后微裂缝特征；e.自发吸水7 d后微裂缝特征；f.自发吸水14 d后微裂缝特征。
Figure 8. Evolution characteristics of micro-fractures between clay minerals and organic matter at different times of spontaneous water imbibition for sample Z207-1 from Long 1-1 sub-member in western Chongqing area, Sichuan Basin
图 9 四川盆地渝西地区龙一1亚段页岩样品自发吸水前后微观孔隙变化特征
a.Z203-1号样品自发吸水前孔隙及矿物分布特征；b.Z207-1号样品自发吸水前孔隙及矿物分布特征；c.Z203H2-1号样品自发吸水前孔隙及矿物分布特征；d.Z203-1号样品自发吸水14 d后孔隙发育特征；e. Z207-1号样品自发吸水14 d后孔隙发育特征；f.Z203H2-1号样品自发吸水14 d后孔隙发育特征。
Figure 9. Variation characteristics of microscopic pores before and after spontaneous water imbibition in shale samples from Long 1-1 sub-member in western Chongqing area, Sichuan Basin
图 10 四川盆地渝西地区龙一1亚段页岩样品微裂缝缝宽(a)和面孔率(b)与自发吸水时间变化关系
Figure 10. Relationship between micro-fracture width (a) and surface porosity (b) and spontaneous water imbibition time in shale samples from Long 1-1 sub-member in western Chongqing area, Sichuan Basin
图 11 四川盆地渝西地区龙一1亚段不同页岩样品吸水过程中微观结构演变特征
a.样品Z203-1吸水过程中孔隙面积、累计面孔率与孔径关系；b.样品Z207-1吸水过程中孔隙面积、累计面孔率与孔径关系；c.样品Z203H2-1吸水过中程孔隙面积、累计面孔率与孔径关系。
Figure 11. Evolution characteristics of microscopic structure during water imbibition in different shale samples from Long 1-1 sub-member in western Chongqing area, Sichuan Basin
图 12 四川盆地渝西地区龙一1亚段页岩吸水第7 d较吸水前面孔率增幅与岩样孔隙度(a)和渗透率(b)的相关性
Figure 12. Correlation between increase in surface porosity and sample porosity (a) and permeability (b) in shale samples from Long 1-1 sub-member in western Chongqing area, Sichuan Basin on the 7th day of water imbibition compared to before imbibition
表 1 四川盆地渝西地区龙一1亚段页岩样品TOC含量、物性及矿物组成统计
Table 1. TOC content, physical properties, and mineral composition of shale samples from Long 1-1 sub-member in western Chongqing area, Sichuan Basin
样品编号 孔隙度/ % 渗透率/ 10-3μm2 ω(TOC)/ % 矿物含量/% 石英 斜长石 方解石 白云石 黄铁矿 黏土矿物 Z203-1 4.23 0.32 4.8 70.1 3.7 4.3 7.0 3.2 11.7 Z207-1 4.10 0.28 4.5 53.0 6.0 4.0 20.0 4.0 13.0 Z203H2-1 6.05 0.58 5.6 42.5 4.0 12.0 22.0 3.5 16.0 Z208-1 4.90 0.62 4.3 30.4 7.2 5.7 17.7 4.6 34.4 
下载: 导出CSV
-
[1] 邹才能, 赵群, 丛连铸, 等. 中国页岩气开发进展、潜力及前景[J]. 天然气工业, 2021, 41(1): 1-14.ZOU Caineng, ZHAO Qun, CONG Lianzhu, et al. Development progress, potential and prospect of shale gas in China[J]. Natural Gas Industry, 2021, 41(1): 1-14. [2] 才能, 董大忠, 王玉满, 等. 中国页岩气特征、挑战及前景(二)[J]. 石油勘探与开发, 2016, 43(2): 166-178. doi: 10.11698/PED.2016.02.02ZOU Caineng, DONG Dazhong, WANG Yuman, et al. Shale gas in China: characteristics, challenges and prospects(Ⅱ)[J]. Petroleum Exploration and Development, 2016, 43(2): 166-178. doi: 10.11698/PED.2016.02.02 [3] 高岳, 王涛, 严子铭, 等. 页岩气高效开采中钻井完井和水力压裂的关键力学问题[J]. 力学学报, 2022, 54(8): 2248-2268.GAO Yue, WANG Tao, YAN Ziming, et al. Key mechanical problems of well drilling and completion and hydraulic fracture in highly efficient extraction of shale gas[J]. Chinese Journal of Theoretical and Applied Mechanics, 2022, 54(8): 2248-2268. [4] CHENG Yueming. Impact of water dynamics in fractures on the performance of hydraulically fractured wells in gas-shale reservoirs[J]. Journal of Canadian Petroleum Technology, 2012, 51(2): 143-151. doi: 10.2118/127863-PA [5] ALKOUH A. New advances in shale gas reservoir analysis using water flowback data[D]. College Station: Texas A&M University, 2014. [6] DEHGHANPOUR H, ZUBAIR H A, Chhabra A, et al. Liquid intake of organic shales[J]. Energy & Fuels, 2012, 26(9): 5750-5758. [7] 廖如刚, 赵志红, 李婷, 等. 页岩储层吸水能力影响因素实验[J]. 天然气勘探与开发, 2019, 42(2): 113-117.LIAO Rugang, ZHAO Zhihong, LI Ting, et al. Experimental study on the factors influencing water absorption capacity of shale reservoirs[J]. Natural Gas Exploration and Development, 2019, 42(2): 113-117. [8] 康治勇. 页岩浸水力学弱化及渗透性演化规律研究[D]. 重庆: 重庆大学, 2019.KANG Zhiyong. Research on the weakening mechanism of the soaked shale and corresponding permeability evolution[D]. Chongqing: Chongqing University, 2019. [9] 林魂. 页岩气储层压后返排评估研究[D]. 北京: 中国石油大学(北京), 2017.LIN Hun. Research on post-frac flowback of shale gas reservoirs[D]. Beijing: China University of Petroleum (Beijing), 2017. [10] 杨柳, 冷润熙, 常天全, 等. 页岩气储层渗吸与盐离子扩散相关关系[J]. 中国海上油气, 2020, 32(2): 112-119.YANG Liu, LENG Runxi, CHANG Tianquan, et al. Correlation between the imbibition and salt ion diffusion of shale gas reservoirs[J]. China Offshore Oil and Gas, 2020, 32(2): 112-119. [11] 姜桂芹, 王国勇. 页岩气储层吸水特性及其对渗透率的影响[J]. 断块油气田, 2021, 28(4): 530-534.JIANG Guiqin, WANG Guoyong. Water absorption characteristics of shale gas reservoir and its influence on permeability[J]. Fault-Block Oil & Gas Field, 2021, 28(4): 530-534. [12] 高书阳, 豆宁辉, 林永学, 等. 川渝地区龙马溪组页岩储层水化特征评价方法[J]. 石油钻探技术, 2018, 46(3): 20-26.GAO Shuyang, DOU Ninghui, LIN Yongxue, et al. A new method for evaluating the characteristics of hydration in the Longmaxi shale gas reservoir in Sichuan-Chongqing area[J]. Petroleum Drilling Techniques, 2018, 46(3): 20-26. [13] 石秉忠, 夏柏如, 林永学, 等. 硬脆性泥页岩水化裂缝发展的CT成像与机理[J]. 石油学报, 2012, 33(1): 137-142. doi: 10.3969/j.issn.1001-8719.2012.01.024SHI Bingzhong, XIA Bairu, LIN Yongxue, et al. CT imaging and mechanism analysis of crack development by hydration in hard-brittle shale formations[J]. Acta Petrolei Sinica, 2012, 33(1): 137-142. doi: 10.3969/j.issn.1001-8719.2012.01.024 [14] 方朝合, 黄志龙, 葛稚新, 等. 工作液浸泡对页岩裂缝扩展及力学性质影响[J]. 太原理工大学学报, 2015, 46(4): 414-418.FANG Chaohe, HUANG Zhilong, GE Zhixin, et al. The influence of working fluid on fracture propagation and mechanical properties of shale[J]. Journal of Taiyuan University of Technology, 2015, 46(4): 414-418. [15] 薛华庆, 周尚文, 蒋雅丽, 等. 水化作用对页岩微观结构与物性的影响[J]. 石油勘探与开发, 2018, 45(6): 1075-1081.Huaqing, ZHOU Shangwen, JIANG Yali, et al. Effects of hydration on the microstructure and physical properties of shale[J]. Petroleum Exploration and Development, 2018, 45(6): 1075-1081. [16] 穆英, 胡志明, 端祥刚, 等. 页岩吸水对储层的作用机理研究[J]. 天然气与石油, 2020, 38(6): 73-79.MU Ying, HU Zhiming, DUAN Xianggang, et al. Study on shale water absorption mechanism on reservoir[J]. Natural Gas and Oil, 2020, 38(6): 73-79. [17] HERZ-THYHSEN R. J, MILLER Q R S, ROTHER G, et al. Nanoscale interfacial smoothing and dissolution during unconventional reservoir stimulation: implications for hydrocarbon mobilization and transport[J]. ACS Applied Materials and Interfaces, 2021, 13(13): 15811-15819. [18] XUE Huaqing, ZHOU Shangwen, JIANG Yali, et al. Effects of hydration on the microstructure and physical properties of shale[J]. Petroleum Exploration and Development, 2018, 45(6): 1146-1153. [19] CHAKRABORTY N, KARPYN Z T, LIU S, et al. Permeability evolution of shale during spontaneous imbibition[J]. Journal of Natural Gas Science and Engineering, 2017, 38: 590-596. [20] ZHOU Zhou, ABASS H, LI Xiaopeng, et al. Experimental investigation of the effect of imbibition on shale permeability during hydraulic fracturing[J]. Journal of Natural Gas Science and Engineering, 2016, 29: 413-430. [21] 钱斌, 朱炬辉, 杨海, 等. 页岩储集层岩心水化作用实验[J]. 石油勘探与开发, 2017, 44(4): 615-621.QIAN Bin, ZHU Juhui, YANG Hai, et al. Experiments on shale reservoirs plugs hydration[J]. Petroleum Exploration and Development, 2017, 44(4): 615-621. [22] 曾凡辉, 张蔷, 郭建春, 等. 页岩水化及水锁解除机制[J]. 石油勘探与开发, 2021, 48(3): 646-653.ZENG Fanhui, ZHANG Qiang, GUO Jianchun, et al. Mechanisms of shale hydration and water block removal[J]. Petroleum Exploration and Development, 2021, 48(3): 646-653. [23] 曾凡辉, 张蔷, 陈斯瑜, 等. 水化作用下页岩微观孔隙结构的动态表征: 以四川盆地长宁地区龙马溪组页岩为例[J]. 天然气工业, 2020, 40(10): 66-75.ZENG Fanhui, ZHANG Qiang, CHEN Siyu, et al. Dynamic characterization of microscopic pore structures of shale under the effect of hydration: a case study of Longmaxi Formation shale in the Changning area of the Sichuan Basin[J]. Natural Gas Industry, 2020, 40(10): 66-75. [24] 李跃纲, 周安富, 谢伟, 等. 四川盆地南部泸州地区五峰组—龙一1亚段页岩岩相划分及储层发育主控因素[J]. 天然气工业, 2022, 42(8): 112-123.LI Yuegang, ZHOU Anfu, XIE Wei, et al. Lithofacies division and main controlling factors of reservoir development in Wufeng Formation–Long11 sub-member shale in the Luzhou region, south Sichuan Basin[J]. Natural gas industry, 2022, 42(8): 112-123. [25] 舒红林, 何方雨, 李季林, 等. 四川盆地大安区块五峰组—龙马溪组深层页岩地质特征与勘探有利区[J]. 天然气工业, 2023, 43(6): 30-43.SHU Honglin, HE Fangyu, LI Jilin, et al. Geological characteristics and favorable exploration areas of Wufeng Formation-Longmaxi Formation deep shale in the Da'an block, Sichuan Basin[J]. Natural Gas Industry, 2023, 43(6): 30-43. [26] 王宇, 翟成, 余旭, 等. 高温作用下五峰组—龙马溪组页岩动力学特征及损伤演化规律研究[J]. 岩石力学与工程学报, 2023, 42(5): 1110-1123.WANG Yu, ZHAI Cheng, YU Xu, et al. Dynamic characteristics and damage evolution law of Wufeng Formation-Longmaxi Formation shale under high temperature effects[J]. Chinese Journal of Rock Mechanics and Engineering, 2023, 42(5): 1110-1123. [27] 隋微波, 田英英, 姚晨昊. 页岩水化微观孔隙结构变化定点观测实验[J]. 石油勘探与开发, 2018, 45(5): 894-901.SUI Weibo, TIAN Yingying, YAO Chenhao. Investigation of microscopic pore structure variations of shale due to hydration effects through SEM fixed-point observation experiments[J]. Petroleum Exploration and Development, 2018, 45(5): 894-901. [28] 丁江辉, 张金川, 杨超, 等. 页岩有机孔成因演化及影响因素探讨[J]. 西南石油大学学报(自然科学版), 2019, 41(2): 33-44.DING Jianghui, ZHANG Jinchuan, YANG Chao, et al. Formation evolution and influencing factors of organic pores in shale[J]. Journal of Southwest Petroleum University (Science & Technology Edition), 2019, 41(2): 33-44. [29] NIE Haikuan, ZHANG Jinchuan, JIANG Shengling. Types and characteristics of the Lower Silurian shale gas reservoirs in and around the Sichuan Basin[J]. Acta Geologica Sinica (English Edition), 2015, 89(6): 1973-1985. [30] 吉利明, 吴远东, 贺聪, 等. 富有机质泥页岩高压生烃模拟与孔隙演化特征[J]. 石油学报, 2016, 37(2): 172-181.JI Liming, WU Yuandong, HE Cong, et al. High-pressure hydrocarbon-generation simulation and pore evolution characteristics of organic-rich mudstone and shale[J]. Acta Petrolei Sinica, 2016, 37(2): 172-181. [31] 胡文瑄, 姚素平, 陆现彩, 等. 典型陆相页岩油层系成岩过程中有机质演化对储集性的影响[J]. 石油与天然气地质, 2019, 40(5): 947-956.HU Wenxuan, YAO Suping, LU Xiancai, et al. Effects of organic matter evolution on oil reservoir property during diagenesis of typical continental shale sequences[J]. Oil & Gas Geology, 2019, 40(5): 947-956. [32] 聂海宽, 张光荣, 李沛, 等. 页岩有机孔研究现状和展望[J]. 石油学报, 2022, 43(12): 1770-1787.NIE Haikuan, ZHANG Guangrong, LI Pei, et al. Research status and prospect on organic matter pores in shale[J]. Acta Petrolei Sinica, 2022, 43(12): 1770-1787. [33] WANG Qian, HOU Yucui, WU Weize, et al. The structural characteristics of kerogens in oil shale with different density grades[J]. Fuel, 2018, 219: 151-158. [34] 刘磊, 姚军, 孙海, 等. 考虑微裂缝的数字岩心多点统计学构建方法[J]. 科学通报, 2018, 63(30): 3146-3157.LIU Lei, YAO Jun, SUN Hai, et al. Reconstruction of digital rock considering micro-fracture based on multi-point statistics[J]. Chinese Science Bulletin, 2018, 63(30): 3146-3157. [35] 王东英, 姚军, 陈掌星, 等. 页岩微裂缝内气—水两相流动规律[J]. 科学通报, 2019, 64(31): 3232-3243.WANG Dongying, YAO Jun, CHEN Zhangxing, et al. Gas-water two-phase transport properties in shale microfractures[J]. Chinese Science Bulletin, 2019, 64(31): 3232-3243. [36] LIU Xiangjun, ZENG Wei, LIANG Lixi, et al. Experimental study on hydration damage mechanism of shale from the Longmaxi Formation in southern Sichuan Basin, China[J]. Petroleum, 2016, 2(1): 54-60. [37] 郑晓卿, 刘建, 卞康, 等. 鄂西北页岩饱水软化微观机制与力学特性研究[J]. 岩土力学, 2017, 38(7): 2022-2028.ZHENG Xiaoqing, LIU Jian, BIAN Kang, et al. Softening micro-mechanism and mechanical properties of water-saturated shale in northwestern Hubei[J]. Rock and Soil Mechanics, 2017, 38(7): 2022-2028. -
计量
- 文章访问数: 50
- HTML全文浏览量: 11
- PDF下载量: 15
- 被引次数: 0
苏公网安备32021102000780号