Fracture Evolution and Mechanical Properties of Deep Shales Under Spontaneous Imbibition

doi:10.7657/XJPG20250210

Abstract

Abstract:

The mechanism of fracture propagation and changes in mechanical properties of deep shale reservoirs caused by the imbibition of fracturing fluid after hydraulic fracturing remain unclear. By CT scanning, continuous scratch testing, and overburden pressure porosity-permeability testing, as well as spontaneous imbibition experiments, the fracture propagation patterns, changes in rock mechanics, and variations in physical properties before and after imbibition were comprehensively evaluated. The results show that imbibition promotes the activation, propagation, and interconnection of shale beddings and pre-existing microcracks, forming a more complex fracture network to enhance reservoir porosity and permeability. The development of fracture and bedding plane reduce the overall strength and stability of rock, demonstrating a dual effect of improving fluid transport capacity while weakening mechanical performance. Under limited crack propagation conditions, the increase in porosity and permeability is modest. When a complex fracture network is developed, reservoir porosity and permeability significantly improve, and mechanical weakening becomes more pronounced. In the evaluation and stimulation design of unconventional reservoirs, it is essential to balance the fracture network induced by spontaneous imbibition to account for its impact on reservoir flow conditions and formation stability.

Key words: deep shale, imbibition, fracture propagation, rock mechanics, hydraulic fracturing, physical property, continuous scratch test, CT scanning

CLC Number:

TE357

FANG Zheng, CHEN Mian, LI Ji, WEI Shiming, KAO Jiawei, MAO Yu. Fracture Evolution and Mechanical Properties of Deep Shales Under Spontaneous Imbibition[J]. Xinjiang Petroleum Geology, 2025, 46(2): 208-216.

Figures/Tables 9

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Table 1.

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Table 2.

Fig. 7.

References 36

[1]	邹才能, 朱如凯, 董大忠, 等. 页岩油气科技进步、发展战略及政策建议[J]. 石油学报, 2022, 43(12):1675-1686. doi: 10.7623/syxb202212001
	ZOU Caineng, ZHU Rukai, DONG Dazhong, et al. Scientific and technological progress,development strategy and policy suggestion regarding shale oil and gas[J]. Acta Petrolei Sinica, 2022, 43(12):1675-1686. doi: 10.7623/syxb202212001
[2]	鲜成钢, 金衍, 李斌会, 等. 页岩油气地质-工程一体化理论与技术研究进展[J]. 钻采工艺, 2024, 47(6):8-15.
	XIAN Chenggang, JIN Yan, LI Binhui, et al. Research progress on theory and technology of shale oil and gas geo-engineering integration[J]. Drilling & Production Technology, 2024, 47(6):8-15.
[3]	赵金洲, 雍锐, 胡东风, 等. 中国深层—超深层页岩气压裂:问题、挑战与发展方向[J]. 石油学报, 2024, 45(1):295-311. doi: 10.7623/syxb202401017
	ZHAO Jinzhou, YONG Rui, HU Dongfeng, et al. Deep and ultra-deep shale gas fracturing in China:Problems,challenges and directions[J]. Acta Petrolei Sinica, 2024, 45(1):295-311. doi: 10.7623/syxb202401017
[4]	王光付, 李凤霞, 王海波, 等. 四川盆地不同类型页岩气压裂难点和对策[J]. 石油与天然气地质, 2023, 44(6):1378-1392.
	WANG Guangfu, LI Fengxia, WANG Haibo, et al. Difficulties and countermeasures for fracturing of various shale gas reservoirs in the Sichuan Basin[J]. Oil & Gas Geology, 2023, 44(6):1378-1392.
[5]	马振乾, 周浪, 左宇军, 等. 薄层状红页岩细观破坏特性研究[J]. 煤田地质与勘探, 2023, 51(10):104-113.
	MA Zhenqian, ZHOU Lang, ZUO Yujun, et al. Study on mesoscopic failure characteristics of layered red shale[J]. Coal Geology & Exploration, 2023, 51(10):104-113.
[6]	李彦伟, 朱超凡, 曾壹坚, 等. 层理特征对油页岩水力压裂裂缝扩展规律影响的数值模拟研究[J]. 煤田地质与勘探, 2023, 51(11):44-54.
	LI Yanwei, ZHU Chaofan, ZENG Yijian, et al. Numerical simulations of the effects of bedding planes on hydraulic fracture propagation law in oil shale[J]. Coal Geology & Exploration, 2023, 51(11):44-54.
[7]	李玉伟, 李子健, 邵力飞, 等. 基于物理信息约束的页岩油储层可压性评价新方法[J]. 煤田地质与勘探, 2023, 51(10):37-51.
	LI Yuwei, LI Zijian, SHAO Lifei, et al. A new physics-informed method for the fracability evaluation of shale oil reservoirs[J]. Coal Geology & Exploration, 2023, 51(10):37-51.
[8]	赵振峰, 王文雄, 徐晓晨, 等. 鄂尔多斯盆地海相深层页岩气压裂技术[J]. 石油钻探技术, 2023, 51(5):23-32.
	ZHAO Zhenfeng, WANG Wenxiong, XU Xiaochen, et al. Hydraulic fracturing technology for deep marine shale gas in Ordos Basin[J]. Petroleum Drilling Techniques, 2023, 51(5):23-32.
[9]	万海乔, 王盛, 刘学良. 低孔低渗稠油油藏注水增能效果影响因素[J]. 新疆石油地质, 2023, 44(3):347-351.
	WAN Haiqiao, WANG Sheng, LIU Xueliang. Factors influencing water injection effect in low porosity and low permeability heavy oil reservoirs[J]. Xinjiang Petroleum Geology, 2023, 44(3):347-351.
[10]	万涛, 张景, 董岩. 玛湖凹陷致密砾岩油藏不同开发方式下原油微观可动性[J]. 新疆石油地质, 2024, 45(3):327-333.
	WAN Tao, ZHANG Jing, DONG Yan. Microscopic oil mobility in tight conglomerate reservoirs under different development modes,Mahu sag[J]. Xinjiang Petroleum Geology, 2024, 45(3):327-333.
[11]	王鑫, 曾溅辉, 孔祥晔, 等. 页岩孔隙润湿性对自发渗吸的控制作用[J]. 中南大学学报(自然科学版), 2022, 53(9):3323-3336.
	WANG Xin, ZENG Jianhui, KONG Xiangye, et al. Controlling effect of shale pore wettability on spontaneous imbibition[J]. Journal of Central South University(Science and Technology), 2022, 53(9):3323-3336.
[12]	ZHOU Yang, YOU Lijun, KANG Yili, et al. Experimental study of the fracture initiation through the synergy of spontaneous imbibition and hydration of residual fracturing fluids in shale gas reservoirs[J]. Journal of Natural Gas Science and Engineering, 2022,102:104577.
[13]	丁乙, 刘向君, 曹雯, 等. 页岩渗吸过程中的水化损伤演化特征研究[J]. 工程地质学报, 2024, 32(4):1262-1272.
	DING Yi, LIU Xiangjun, CAO Wen, et al. Research on characteristics of hydration damage evolution of shale during spontaneous imbibition[J]. Journal of Engineering Geology, 2024, 32(4):1262-1272.
[14]	闫传梁, 邓金根, 蔚宝华, 等. 页岩气储层井壁坍塌压力研究[J]. 岩石力学与工程学报, 2013, 32(8):1595-1602.
	YAN Chuanliang, DENG Jingen, YU Baohua, et al. Research on collapsing pressure of gas shale[J]. Chinese Journal of Rock Mechanics and Engineering, 2013, 32(8):1595-1602.
[15]	郭建春, 陶亮, 胡克剑, 等. 页岩储层水相渗吸作用规律实验[J]. 石油学报, 2022, 43(9):1295-1304. doi: 10.7623/syxb202209008
	GUO Jianchun, TAO Liang, HU Kejian, et al. Experiment on imbibition law of aqueous phase in shale reservoir[J]. Acta Petrolei Sinica, 2022, 43(9):1295-1304. doi: 10.7623/syxb202209008
[16]	邸士莹, 程时清, 白文鹏, 等. 致密油藏动态裂缝扩展机理及应用[J]. 力学学报, 2021, 53(8):2141-2155.
	DI Shiying, CHENG Shiqing, BAI Wenpeng, et al. Dynamic fracture propagation mechanism and application in tight oil reservoir[J]. Chinese Journal of Theoretical and Applied Mechanics, 2021, 53(8):2141-2155.
[17]	申颍浩, 葛洪魁, 宿帅, 等. 页岩气储层的渗吸动力学特性与水锁解除潜力[J]. 中国科学:物理学力学天文学, 2017, 47(11):84-94.
	SHEN Yinghao, GE Hongkui, SU Shuai, et al. Imbibition characteristic of shale gas formation and water-block removal capability[J]. Scientia Sinica:Physica,Mechanica & Astronomica, 2017, 47(11):84-94.
[18]	WANG Daobing, WANG Xiaoqiong, GE Hongkui, et al. Insights into the effect of spontaneous fluid imbibition on the formation mechanism of fracture networks in brittle shale:An experimental investigation[J]. ACS Omega, 2020, 5(15):8847-8857. doi: 10.1021/acsomega.0c00452 pmid: 32337447
[19]	GUO Yide, LI Xibing, HUANG Linqi. Insight into spontaneous water-based working fluid imbibition on the dynamic tensile behavior of anisotropic shale[J]. Engineering Geology, 2022,308:106830.
[20]	LI Bo, YU Hao, JI Dongqi, et al. Pore-scale imbibition patterns in layered porous media with fractures[J]. Physics of Fluids, 2024, 36(1):1-16.
[21]	GOU Qiyang, XU Shang, HAO Fang, et al. Making sense of micro-fractures to the Longmaxi shale reservoir quality in the Jiaoshiba area,Sichuan Basin,China:Implications for the accumulation of shale gas[J]. Journal of Natural Gas Science and Engineering, 2021,94:104107.
[22]	YU Fei, HAN Rujun, XU Ke. Countercurrent imbibition in porous media with dense and parallel microfractures:Numerical and analytical study[J]. SPE Journal, 2024, 29(10):5658-5677.
[23]	尹丛彬. 页岩压裂裂缝渗透率的测试与分析[J]. 天然气工业, 2018, 38(3):60-68.
	YIN Congbin. Test and analysis on the permeability of fractured fractures in shale reservoirs[J]. Natural Gas Industry, 2018, 38(3):60-68.
[24]	韦世明, 金衍, 夏阳, 等. 自发渗吸对页岩油储层压裂后闷井的影响[J]. 石油钻采工艺, 2023, 45(6):756-765.
	WEI Shiming, JIN Yan, XlA Yang, et al. Influence of spontaneous imbibition on post-fracturing well soaking in shale oil reservoirs[J]. Oil Drilling & Production Technology, 2023, 45(6):756-765.
[25]	刘洪涛, 薄克浩, 金衍, 等. 基于连续划痕实验确定复杂地层岩石强度参数的方法研究[J]. 石油科学通报, 2022, 7(4):532-542.
	LIU Hongtao, BO Kehao, JIN Yan, et al. Determination of rock strength parameters during drilling based on continuous scratch tests[J]. Petroleum Science Bulletin, 2022, 7(4):532-542.
[26]	DETOURNAY E, DEFOURNY P. A phenomenological model for the drilling action of drag bits[J]. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1992, 29(1):13-23.
[27]	RICHARD T, DAGRAIN F, POYOL E, et al. Rock strength determination from scratch tests[J]. Engineering Geology, 2012,147:91-100.
[28]	Hatheway A W. The complete ISRM suggested methods for rock characterization,testing and monitoring[J]. Bulletin of Engineering Geology and the Environment, 2009, 68(2):287-288.
[29]	FISHER Q J, GRATTONI C, RYBALCENKO K, et al. Laboratory measurements of porosity and permeability of shale[C]. Catania, Italy: Fifth EAGE Shale Workshop, 2016.
[30]	FIROUZI M, ALNOAIMI K, KOVSCEK A, et al. Klinkenberg effect on predicting and measuring helium permeability in gas shales[J]. International Journal of Coal Geology, 2014,123:62-68.
[31]	CHEN Yufei, JIANG Changbao, YIN Guangzhi, et al. Permeability evolution under true triaxial stress conditions of Longmaxi shale in the Sichuan Basin,southwest China[J]. Powder Technology, 2019,354:601-614.
[32]	LI Wenfeng, FRASH L P, WELCH N J, et al. Stress-dependent fracture permeability measurements and implications for shale gas production[J]. Fuel, 2021,290:119984.
[33]	WANG Chaolin, PAN Lehua, ZHAO Yu, et al. Analysis of the pressure-pulse propagation in rock:A new approach to simultaneously determine permeability,porosity,and adsorption capacity[J]. Rock Mechanics and Rock Engineering, 2019,52:4301-4317.
[34]	YANG Zehao, SANG Qian, DONG Mingzhe, et al. A modified pressure-pulse decay method for determining permeabilities of tight reservoir cores[J]. Journal of Natural Gas Science and Engineering, 2015,27:236-246.
[35]	ZHANG Xin, FEI Zheng, ZHONG Wenwu, et al. Research and implementation of three-dimensional spatial information characterization and visualization of fractures in deteriorated sandstone[J]. Buildings, 2023, 13(10):2418.
[36]	衡帅, 杨春和, 郭印同, 等. 层理对页岩水力裂缝扩展的影响研究[J]. 岩石力学与工程学报, 2015, 34(2):228-237.
	HENG Shuai, YANG Chunhe, GUO Yintong, et al. Influence of bedding planes on hydraulic fracture propagation in shale formations[J]. Chinese Journal of Rock Mechanics and Engineering, 2015, 34(2):228-237.

参数	数值
水平位移精度/mm	0.1
划痕深度精度/mm	0.001
数据点精度/（pts·mm^-1）	10
尖刀头宽度/mm	10
钝刀头宽度/mm	10
钝刀头摩擦面长度/mm	1

样品编号	状态	平均单轴抗压强度/MPa	内摩擦角/（°）	内聚力/MPa
样品1	渗吸前	95.24	36.92	15.14
样品1	渗吸后	81.89	34.06	13.88
样品2	渗吸前	89.78	35.29	14.92
样品2	渗吸后	76.14	34.02	13.65
样品3	渗吸前	92.33	35.89	14.44
样品3	渗吸后	66.13	31.79	12.08
样品4	渗吸前	91.25	36.17	14.87
样品4	渗吸后	63.24	32.01	12.53