选取四川盆地长宁地区龙马溪组页岩样品,开展电镜扫描、CT扫描、高压压汞、低温N2吸附、水化自吸等实验,对比蒙脱石、伊利石水化特征,分析页岩水锁解除能力的主控因素,揭示页岩水化过程中孔隙结构的演变机制。研究表明:页岩水化特征与黏土组成密切相关,伊利石含量高的页岩不易水化膨胀,改善储集层孔隙结构的能力有限;蒙脱石含量高则易水化膨胀,改善储集层孔隙结构的潜力较大;页岩伊利石含量高,初期自吸作用相对较强,但扩散能力不足,易形成水锁;页岩蒙脱石含量高,初期自吸作用相对较弱,扩散能力较好,具有一定的水锁解除能力;页岩存在最佳水化时间,此时储集层物性最好,水化时间过长,则对储集层物性形成伤害,伊利石含量高的页岩最佳水化时间较短;无机阳离子对黏土矿物吸水膨胀具有抑制作用,对伊利石的抑制作用更强,K+抑制效果较好,蒙脱石含量高的储集层可以通过降低压裂液阳离子含量促进黏土水化作用;伊利石含量高的储集层可注入高K+含量的压裂液抑制水化作用。图13表2参25
Shale samples of Longmaxi Formation in the Changning area of the Sichuan Basin were selected to carry out scanning electron microscopy, CT imaging, high-pressure mercury injection, low-temperature nitrogen adsorption and imbibition experiments to compare the hydration characteristics of montmorillonite and illite, analyze the main factors affecting the water block removal of shale, and reveal the mechanisms of pore structure evolution during shale hydration. The hydration characteristics of shale are closely related to the composition of clay minerals, the shale with high illite content is not susceptible to hydration and thus has limited room for pore structure improvement; the shale with high montmorillonite is susceptible to hydration expansion and thus has higher potential of pore structure improvement by stimulation; the shale with high illite content has stronger imbibition in the initial stage, but insufficient diffusion ability, and thus is likely to have water block; the shale with high montmorillonite content has weaker imbibition in the initial stage but better water diffusion, so water blocking in this kind of shale can be removed to some degree; the shale reservoir has an optimal hydration time, when it is best in physical properties, but hydration time too long would cause damage to the reservoir, and the shale with high illite content has a shorter optimal hydration time; inorganic cations can inhibit the hydration of clay minerals and have stronger inhibition to illite expansion, especially K+; for the reservoir with high content of montmorillonite, the cation content of fracturing fluid can be lowered to promote the shale hydration; fracturing fluid with high K+ content can be injected into reservoirs with high illite content to suppress hydration.
[1] 邹才能, 潘松圻, 荆振华, 等. 页岩油气革命及影响[J]. 石油学报, 2020, 41(1): 1-12.
ZOU Caineng, PAN Songqi, JING Zhenhua, et al. Shale oil and gas revolution and its impact[J]. Acta Petrolei Sinica, 2020, 41(1): 1-12.
[2] ZENG F, PENG F, GUO J, et al. A transient productivity model of fractured wells in shale reservoirs based on the succession pseudo-steady state method[J]. Energies, 2018, 11(9): 2335.
[3] AMIRHOSSEIN A, MOJTABA G, MASOUD R.采用新标度方程预测再渗吸作用下天然裂缝性储集层重力泄油采收率[J]. 石油勘探与开发, 2020, 47(6): 1212-1219.
AMIRHOSSEIN A, MOJTABA G, MASOUD R. Prediction of oil recovery in naturally fractured reservoirs subjected to reinfiltration during gravity drainage using a new scaling equation[J]. Petroleum Exploration and Development, 2020, 47(6): 1212-1219.
[4] ZENG F, ZHANG Y, GUO J, et al. Optimized completion design for triggering a fracture network to enhance horizontal shale well production[J]. Journal of Petroleum Science and Engineering, 2020, 190(1): 1-16.
[5] JIANG G, LI Y, ZHANG M. Evaluation of gas wettability and its effects on fluid distribution and fluid flow in porous media[J]. Petroleum Science, 2013, 10(4): 515-527.
[6] BERTONCELLO A, WALLACE J, BLYTON C, et al. Imbibition and water blockage in unconventional reservoirs: Well-management implications during flowback and early production[J]. SPE Reservoir Evaluation and Engineering, 2014, 17(4): 497-506.
[7] 张磊, 康钦军, 姚军, 等. 页岩压裂中压裂液返排率低的孔隙尺度模拟与解释[J]. 科学通报, 2014, 59(32): 3197-3203.
ZHANG Lei, KANG Qinjun, YAO Jun, et al. The explanation of low recovery of fracturing fluid in shale hydraulic fracturing by pore-scale simulation[J]. Chinese Science Bulletin, 2014, 59(32): 3197-3203.
[8] CHENG Y. 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.
[9] ZENG F, ZHANG Q, GUO J, et al. Analytical spontaneous imbibition model for confined nanofractures[J]. Journal of Geophysics and Engineering, 2020, 17(4): 635-642.
[10] 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.
[11] HOWER W F. Influence of clays on the production of hydrocarbons[R]. Louisiana: SPE Symposium on Formation Damage Control, 1974.
[12] FARAH N, DING D Y, WU Y S. Simulation of the impact of fracturing-fluid-induced formation damage in shale gas reservoirs[J]. SPE Reservoir Evaluation and Engineering, 2017, 20(3): 532-546.
[13] 康毅力, 杨斌, 李相臣, 等. 页岩水化微观作用力定量表征及工程应用[J]. 石油勘探与开发, 2014, 44(2): 301-308.
KANG Yili, YANG Bin, LI Xiangchen, et al. Quantitative characterization of micro forces in shale hydration and field applications[J]. Petroleum Exploration and Development, 2014, 44(2): 301-308.
[14] 冒海军, 郭印同, 王光进, 等. 黏土矿物组构对水化作用影响评价[J]. 岩土力学, 2010, 31(9): 2723-2728.
MAO Haijun, GUO Yintong, WANG Guangjin, et al. Evaluation of impact of clay mineral fabrics on hydration process[J]. Rock and Soil Mechanics, 2010, 31(9): 2723-2728.
[15] GHANBARI E, DEHGHANPOUR H. The fate of fracturing water: A field and simulation study[J]. Fuel, 2015, 163: 282-294.
[16] GOU Q, XU S, HAO F, et al. Full-scale pores and micro-fractures characterization using FE-SEM, gas adsorption, nano-CT and micro-CT: A case study of the Silurian Longmaxi Formation shale in the Fuling area, Sichuan Basin, China[J]. Fuel, 2019, 253: 167-179.
[17] ZENG F, ZHANG Y, GUO J, et al. Prediction of shale apparent liquid permeability based on fractal theory[J]. Energy and Fuels, 2020, 34(6): 6822-6833.
[18] BOER J H D, LINSEN B G, PLAS T V D, et al. Studies on pore systems in catalysts: VII. Description of the pore dimensions of carbon blacks by the t method[J]. Journal of Catalysis, 1965, 4(6): 649-653.
[19] SING K. Reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity[J]. Pure and Applied Chemistry, 1982, 54(11): 2201-2218.
[20] KLIMAKOW M, KLOBES P, RADEMANN K, et al. Characterization of mechanochemically synthesized MOFs[J]. Microporous and Mesoporous Materials, 2012, 154: 113-118.
[21] HU Q, EWING R P, DULTZ S. Low pore connectivity in natural rock[J]. Journal of Contaminant Hydrology, 2012, 133(1): 76-83.
[22] YANG Y, YAO J, WANG C, et al. New pore space characterization method of shale matrix formation by considering organic and inorganic pores[J]. Journal of Natural Gas Science and Engineering, 2015, 27(2): 496-503.
[23] ZENG F, ZHANG Y, GUO J, et al. A unified multiple transport mechanism model for gas through shale pores[J]. Geofluids, 2020, 2020(2): 1-17.
[24] ZENG F, PENG F, GUO J, et al. Gas mass transport model for microfractures considering the dynamic variation of width in shale reservoirs[J]. SPE Reservoir Evaluation and Engineering, 2019, 22(4): 1265-1281.
[25] ROSHAN H, EHSANI S, MARJO C E, et al. Mechanisms of water adsorption into partially saturated fractured shales: An experimental study[J]. Fuel, 2015, 159: 628-637.
