Characterization of irregular complex fractures in unconventional oil and gas reservoirs
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摘要: 非常规油气资源储量大，开发难度高。储层压裂改造是非常规油气资源开发的关键技术手段。天然裂缝和压裂裂缝具有不规则性和复杂性。针对现有裂缝表征方法难以准确刻画裂缝真实形状和宽度变化等不规则特性这一问题，提出了基于非结构PEBI网格的不规则复杂裂缝表征方法。首先，建立基于PEBI网格的天然裂缝表征流程，实现对任意区域或限定区域天然裂缝的准确表征；其次，建立基于Delaunay三角形网格和PEBI网格的压裂裂缝表征及优化方法，分析网格尺寸及优化次数对裂缝表征精度的影响；第三，建立基于非结构网格的非平面裂缝表征方法，实现对弯曲裂缝的刻画和表征，裂缝形态和分布与实际情况更相符；第四，提出非均匀裂缝宽度表征方法，实现对变宽度即同一条裂缝宽度和导流能力不均匀分布裂缝的精细表征；第五，在全区域和限定区域内，实现耦合不规则压裂裂缝和不规则天然裂缝的复杂缝网表征。针对大规模天然裂缝与压裂裂缝相交、裂缝宽度非均匀分布、非平面裂缝等复杂条件下的裂缝网络表征，通过调整网格优化次数，能够提高缝网表征质量。利用PEBI网格能够灵活准确逼近裂缝复杂边界条件的优势，实现快速、准确地显示处理大量不规则天然裂缝和压裂裂缝。形成的不规则复杂裂缝表征方法，有助于提高非常规油气藏裂缝网络的表征精度和数值模拟计算准确性。Abstract: Unconventional oil and gas resources have large reserves and are difficult to develop. Reservoir fracturing is a key technical means for the development of unconventional oil and gas resources. Natural fractures and induced fractures are irregular and complex. To address the issue that existing fracture characterization methods cannot accurately depict the true shapes and width variations of fractures, a method based on unstructured PEBI grids for characterizing irregular and complex fractures was proposed. First, a natural fracture characterization process based on PEBI grids was established, allowing for accurate characterization of natural fractures in any region or a specified area. Second, a characterization and optimization method for induced fractures based on Delaunay triangulation and PEBI grids was developed, analyzing the impact of grid size and optimization iterations on fracture characterization accuracy. Third, a method for characterizing non-planar fractures using unstructured grids was established, enabling the depiction of curved fractures, making the fracture morphology and distribution more consistent with actual conditions. Fourth, a method for characterizing non-uniform fracture width was proposed, achieving fine characterization of fractures with non-uniform distribution of width and conductivity along the same fracture. Fifth, a complex fracture network characterization method coupling irregular induced fractures and irregular natural fractures in the whole area and specified regions was realized. For fracture network characterization under complex conditions such as large-scale intersections of natural and induced fractures, non-uniform fracture width distribution, and non-planar frac- tures, adjusting the number of grid optimization iterations could improve the quality of the fracture network characterization. Utilizing the advantage of PEBI grids to flexibly and accurately approximate complex fracture boundary conditions, this method enabled the rapid and accurate handling of a large number of irregular natural and induced fractures. The developed method for characterizing irregular and complex fractures helps improve the accuracy of fracture network characterization and numerical simulation calculations in unconventional oil and gas reservoirs.
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图 1 基于PEBI网格的天然裂缝表征流程
Figure 1. Characterization workflow of natural fractures based on PEBI grids
图 2 天然裂缝随机分布表征结果
Figure 2. Characterization of randomly distributed natural fractures in arbitrary and designated areas
图 3 优化次数对压裂水平井Delaunay三角形网格(左)和PEBI网格(右)生产质量的影响
Figure 3. Effect of iteration steps on Delaunay triangular grid (left) and PEBI grid (right)
图 4 网格尺寸对压裂水平井Delaunay三角形网格(左)和PEBI网格(右)的影响
Figure 4. Effect of initial grid size on Delaunay triangular grid (left) and PEBI grid (right)
图 5 不同网格尺寸下的裂缝附近PEBI网格放大图
Figure 5. Enlarged views of PEBI grids around fractures under different initial grid sizes
图 6 多条非平面裂缝的非结构网格剖分及局部放大图
Figure 6. Characterization of non-planar fractures based on Delaunay triangular grid and PEBI grid and enlarged views of PEBI grids in x-y plane
图 8 裂缝非均匀宽度值和裂缝宽度均匀分布、非均匀分布下的非结构网格划分
Figure 8. Value of non-uniform fracture aperture and characterization of fractures with uniform and non-uniform fracture apertures using unstructured grids
图 9 裂缝宽度非均匀变化的非结构网格划分及PEBI网格局部放大图
Figure 9. Characterization of fractures with non-uniform fracture aperture based on unstructured grid and zoom-in view in x-y plane
图 10 非平面变宽度裂缝表征(PEBI网格局部放大图)
Figure 10. Characterization of non-planar fractures with non-uniform fracture aperture based on PEBI grids
图 11 基于PEBI网格的裂缝宽度均匀变化和等差递减分布的裂缝表征
Figure 11. Characterization of fractures with uniform fracture aperture and arithmetic decreasing fracture aperture based on PEBI grids
图 12 压裂水平井(平面裂缝)和随机分布的天然裂缝网络表征结果
Figure 12. Characterization of fracture networks with MFHW (planar fractures) and randomly distributed natural fractures based on PEBI grids
图 13 压裂水平井非平面压裂裂缝和限定区域内随机分布的天然裂缝表征
Figure 13. Characterization of fracture networks with MFHW (non-planar fractures) and randomly distributed natural fractures in designated areas
表 1 储层、井筒、裂缝(均匀宽度和非均匀宽度)的基础参数
Table 1. Basic parameters of reservoirs, wellbores, and fractures with uniform and non-uniform apertures
参数类型 数值 参数类型 数值 储层长度/m 2 500 裂缝数量/条 6 储层宽度/m 1 000 井筒半径/m 0.10 储层高度/m 50 水平井长度/m 1 550 裂缝均匀宽度/m 0.03 压裂裂缝非均匀宽度参数 μ=-1.0 σ=0.531 7 
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表 2 储层、井筒、裂缝(非均匀宽度)的基础参数
Table 2. Basic parameters of reservoirs, wellbores, and fractures with non-uniform apertures
参数类型 数值 参数类型 数值 储层长度/m 1 000 裂缝数量/条 3 储层宽度/m 1 000 裂缝半长/m 200 储层高度/m 50 压裂裂缝非均匀宽度参数 μ=-0.5
σ=0.4井筒半径/m 0.10 水平井长度/m 600
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[1] 郭建春, 路千里, 何佑伟. 页岩气压裂的几个关键问题与探索[J]. 天然气工业, 2022, 42(8): 148-161. https://www.cnki.com.cn/Article/CJFDTOTAL-TRQG202208010.htmGUO Jianchun, LU Qianli, HE Youwei. Key issues and explorations in shale gas fracturing[J]. Natural Gas Industry, 2022, 42(8): 148-161. https://www.cnki.com.cn/Article/CJFDTOTAL-TRQG202208010.htm [2] 蔡文, 王伟, 梅俊伟, 等. 南川常压页岩气地质特征及水平井参数优化研究: 以东胜区块SY1井区为例[J]. 非常规油气, 2022, 9(3): 83-89. https://www.cnki.com.cn/Article/CJFDTOTAL-FCYQ202203010.htmCAI Wen, WANG Wei, MEI Junwei, et al. Study on geological characteristics of atmospheric shale gas and optimization of horizontal well parameters in Nanchuan: take the well SY1 area of Dongsheng block as an example[J]. Unconventional Oil & Gas, 2022, 9(3): 83-89. https://www.cnki.com.cn/Article/CJFDTOTAL-FCYQ202203010.htm [3] 梁卫卫, 党海龙, 刘滨, 等. 特低渗透油藏注水诱导动态裂缝实验及数值模拟[J]. 石油实验地质, 2023, 45(3): 566-575. doi: 10.11781/sysydz202303566LIANG Weiwei, DANG Hailong, LIU Bin, et al. Experiment and numerical simulation of water injection induced dynamic fractures in ultra-low permeability reservoirs[J]. Petroleum Geology & Experiment, 2023, 45(3): 566-575. doi: 10.11781/sysydz202303566 [4] 孙珂, 徐珂, 陈清华. 低渗透储层构造裂缝长度表征及应用: 以四川盆地磨溪-高石梯地区寒武系龙王庙组为例[J]. 石油实验地质, 2022, 44(1): 160-169. doi: 10.11781/sysydz202201160SUN Ke, XU Ke, CHEN Qinghua. Characterization of the length of structural fractures in low permeability reservoirs and its application: a case study of Longwangmiao Formation in Moxi-Gaoshiti areas, Sichuan Basin[J]. Petroleum Geology & Experiment, 2022, 44(1): 160-169. doi: 10.11781/sysydz202201160 [5] HE Youwei, HE Zhiyue, TANG Yong, et al. Interwell fracturing interference evaluation in shale gas reservoirs[J]. Geoenergy Science and Engineering, 2023, 231: 212337. doi: 10.1016/j.geoen.2023.212337 [6] 杨林, 刘彧轩, 向斌, 等. 金华-秋林致密气藏直井层内分簇压裂裂缝扩展规律及应用[J]. 钻采工艺, 2021, 44(2): 49-51. https://www.cnki.com.cn/Article/CJFDTOTAL-ZCGY202102013.htmYANG Lin, LIU Yuxuan, XIANG Bin, et al. Fracture propagation of intra-zone cluster fracturing and its application in Jinhua-Qiulin tight gas reservoirs[J]. Drilling & Production Technology, 2021, 44(2): 49-51. https://www.cnki.com.cn/Article/CJFDTOTAL-ZCGY202102013.htm [7] 赵超峰, 田建涛, 任丽莹, 等. 吉林探区X水平井青一段压裂微地震监测解释实例[J]. 非常规油气, 2022, 9(5): 51-58. https://www.cnki.com.cn/Article/CJFDTOTAL-FCYQ202205006.htmZHAO Chaofeng, TIAN Jiantao, REN Liying, et al. An example of microseismic monitoring interpretation of fracturing in Qing1 Member of X horizontal well in Jilin exploration area[J]. Unconventional Oil & Gas, 2022, 9(5): 51-58. https://www.cnki.com.cn/Article/CJFDTOTAL-FCYQ202205006.htm [8] 徐荣利, 郭天魁, 曲占庆, 等. 基于离散裂缝模型的页岩油储层压裂渗吸数值模拟[J]. 工程科学学报, 2022, 44(3): 451-463.XU Rongli, GUO Tiankui, QU Zhanqing, et al. Numerical simulation of fractured imbibition in a shale oil reservoir based on the discrete fracture model[J]. Chinese Journal of Engineering, 2022, 44(3): 451-463. [9] 胡之牮, 李树新, 王建君, 等. 复杂人工裂缝产状页岩气藏多段压裂水平井产能评价[J]. 油气藏评价与开发, 2023, 13(4): 459-466. https://www.cnki.com.cn/Article/CJFDTOTAL-KTDQ202304007.htmHU Zhijian, LI Shuxin, WANG Jianjun, et al. Productivity evaluation of multi-stage fracturing horizontal wells in shale gas reservoir with complex artificial fracture occurrence[J]. Reservoir Evaluation and Development, 2023, 13(4): 459-466. https://www.cnki.com.cn/Article/CJFDTOTAL-KTDQ202304007.htm [10] 彭勇民, 董世雄, 边瑞康, 等. 四川盆地东部页岩气水平井裂缝识别方法及应用[J]. 石油实验地质, 2023, 45(6): 1196-1203. doi: 10.11781/sysydz2023061196PENG Yongming, DONG Shixiong, BIAN Ruikang, et al. Method for identification of fractures in shale gas horizontal wells in eastern Sichuan Basin and its application[J]. Petroleum Geology & Experiment, 2023, 45(6): 1196-1203. doi: 10.11781/sysydz2023061196 [11] 何佑伟, 贺质越, 汤勇, 等. 基于机器学习的页岩气井产量评价与预测[J]. 石油钻采工艺, 2021, 43(4): 518-524. https://www.cnki.com.cn/Article/CJFDTOTAL-SYZC202104016.htmHE Youwei, HE Zhiyue, TANG Yong, et al. Shale gas well production evaluation and prediction based on machine learning[J]. Oil Drilling & Production Technology, 2021, 43(4): 518-524. https://www.cnki.com.cn/Article/CJFDTOTAL-SYZC202104016.htm [12] BARENBLATT G I, ZHELTOV I P, KOCHINA I N. Basic concepts in the theory of seepage of homogeneous liquids in fissured rocks[strata]: Ob osnovnykh predstavleniiakh teorii fil'tratsii odnorodnykh zhidkostei v treshchinovatykh porodakh: PMM vol. 24, no. 5, 1960, pp. 852-864[J]. Journal of Applied Mathematics and Mechanics, 1960, 24(5): 1286-1303. [13] WARREN J E, ROOT P J. The behavior of naturally fractured reservoirs[J]. SPE Journal, 1963, 3(3): 245-255. [14] KAZEMI H, SETH M S, THOMAS G W. The interpretation of interference tests in naturally fractured reservoirs with uniform fracture distribution[J]. SPE Journal, 1969, 4(9): 463-472. [15] DE SWAAN O A. Analytic solutions for determining naturally fractured reservoir properties by well testing[J]. SPE Journal, 1976, 16(3): 117-122. [16] PRUESS K, NARASIMHAN T N. A practical method for modeling fluid and heat flow in fractured porous media[J]. SPE Journal, 1985, 25(1): 14-26. [17] WU Yushu, PRUESS K. A multiple-porosity method for simulation of naturally fractured petroleum reservoirs[J]. SPE Reservoir Engineering, 1988, 3(1): 327-336. [18] PANFILI P, COLIN R, COMINELLI A, et al. Efficient and effective field scale simulation of hydraulic fractured wells: methodology and application[C]//Paper presented at the SPE Reservoir Characterization and Simulation Conference and Exhibition. Abu Dhabi, UAE: Society of Petroleum Engineers, 2015. [19] MOINFAR A, NARR W, HUI M H, et al. Comparison of discrete-fracture and dual-permeability models for multiphase flow in naturally fractured reservoirs[C]//Paper presented at the SPE Reservoir Simulation Symposium. The Woodlands, Texas, USA: Society of Petroleum Engineers, 2011. [20] ODLING N E, GILLESPIE P, BOURGINE B, et al. Variations in fracture system geometry and their implications for fluid flow in fractures hydrocarbon reservoirs[J]. Petroleum Geoscience, 1999, 5(4): 373-384. [21] GILLESPIE P A, HOWARD C B, WALSH J J, et al. Measurement and characterization of spatial distributions of fractures[J]. Tectonophysics, 1993, 226(1/4): 113-141. [22] GALE J E, SCHAEFER R A, CARPENTER A B, et al. Collection, analysis, and integration of discrete fracture data from the Monterey Formation for fractured reservoir simulations[C]//Paper presented at the SPE Annual Technical Conference and Exhibition. Dallas, Texas, USA: Society of Petroleum Engineers, 1991. [23] LEE S H, JENSEN C L, LOUGH M F. Efficient finite-difference model for flow in a reservoir with multiple length-scale fractures[J]. SPE Journal, 2000, 5(3): 268-275. [24] LI Liyong, LEE S H. Efficient field-scale simulation of black oil in a naturally fractured reservoir through discrete fracture networks and homogenized media[J]. SPE Reservoir Evaluation & Engineering, 2008, 11(4): 750-758. [25] MOINFAR A, VARAVEI A, SEPEHRNOORI K, et al. Development of a coupled dual continuum and discrete fracture model for the simulation of unconventional reservoirs[C]//Paper presented at the SPE Reservoir Simulation Symposium. The Woodlands, Texas, USA: Society of Petroleum Engineers, 2023. [26] 周方奇. 低渗透油藏嵌入离散裂缝模型的数值模拟研究[D]合肥: 中国科学技术大学, 2015.ZHOU Fangqi. Embedded discrete fracture model for numerical simulation in low permeability reservoir[D]. Hefei: University of Science and Technology of China, 2015. [27] HE Youwei, QIAO Yu, QIN Jiazheng, et al. A novel method to enhance oil recovery by inter-fracture injection and production through the same multi-fractured horizontal well[J]. Journal of Energy Resources Technology, 2022, 144(4): 043005. [28] MOINFAR A, VARAVEI A, SEPEHRNOORI K, et al. Development of a novel and computationally-efficient discrete-fracture model to study ior processes in naturally fractured reservoirs[C]//Paper presented at the SPE Improved Oil Recovery Symposium. Tulsa, Oklahoma, USA: Society of Petroleum Engineers, 2012. [29] SHAKIBA M, SEPEHRNOORI K. Using Embedded Discrete Fracture Model (EDFM) and microseismic monitoring data to characterize the complex hydraulic fracture networks[C]//Paper presented at the SPE Annual Technical Conference and Exhibition. Houston, Texas, USA: Society of Petroleum Engineers, 2015. [30] SHAKIBA M. Modeling and simulation of fluid flow in naturally and hydraulically fractured reservoirs using Embedded Discrete Fracture Model (EDFM)[D]. Texas: The University of Texas at Austin, 2014. [31] CHAI Zhi, YAN Bicheng, KILLOUGH J E, et al. Dynamic embedded discrete fracture multi-continuum model for the simulation of fractured shale reservoirs[C]//Paper presented at the International Petroleum Technology Conference. Bangkok, Thailand: International Petroleum Technology Conference, 2016. [32] WU Yushu, LI Jianfang, DING D Y, et al. A generalized framework model for the simulation of gas production in unconventional gas reservoirs[J]. SPE Journal, 2014, 19(5): 845-857. [33] JIANG Jiamin, YOUNIS R M. Hybrid coupled discrete-fracture/matrix and multicontinuum models for unconventional-reservoir simulation[J]. SPE Journal, 2016, 21(3): 1009-1027. [34] DING D Y, FARAH N, BOURBIAUX B, et al. Simulation of matrix-fracture interaction in low-permeability fractured unconventional reservoirs[J]. SPE Journal, 2018, 23(4): 1389-1411. [35] YANG D, XUE X, CHEN J. High resolution hydraulic fracture network modeling using flexible dual porosity dual permeability framework[C]//Paper presented at the SPE Western Regional Meeting. Garden Grove, California, USA: Society of Petroleum Engineers, 2018. [36] ŢENE M, BOSMA S B M, Al KOBAISI M S, et al. Projection-based Embedded Discrete Fracture Model (pEDFM)[J]. Advances in Water Resources, 2017, 105: 205-216. [37] CHAI Zhi, TANG Hewei, HE Youwei, et al. Uncertainty quantification of the fracture network with a novel fractured reservoir forward model[C]//Paper presented at the SPE Annual Technical Conference and Exhibition. Dallas, Texas, USA: Society of Petroleum Engineers, 2018. [38] CHAI Zhi. An efficient method for fractured shale reservoir simulation & history matching: the cEDFM approach[D]. Texas: Texas A&M University, 2018. [39] HEINEMANN Z E, BRAND C W. Gridding techniques in reservoir simulation[C]//First and Second International Forum of Reservoir Simulation, Alpbach, Austria, 1989. [40] KARIMI-FARD M, DURLOFSKY L J, AZIZ K. An efficient discrete-fracture model applicable for general-purpose reservoir simulators[J]. SPE Journal, 2004, 9(2): 227-236. [41] SANDVE T H, BERRE I, NORDBOTTEN J M. An efficient multi-point flux approximation method for discrete fracture-matrix simulations[J]. Journal of Computational Physics, 2012, 231(9): 3784-3800. [42] 查文舒. 基于PEBI网格的油藏数值计算及其实现[D]. 合肥: 中国科学技术大学, 2010.ZHA Wenshu. Numerical reservoir calculation on PEBI grids and implementation[D]. Hefei: University of Science and Technology of China, 2010. [43] 王培玺. 低渗透油藏压裂水平井试井解释方法研究[D]. 青岛: 中国石油大学(华东), 2012.WANG Peixi. Fractured horizontal well in low permeability reservoirs research on well testing interpretation method of fractured horizontal well in low permeability reservoirs[D]. Qingdao: China University of Petroleum (East China), 2012. [44] CIPOLLA C L, FITZPATRICK T, WILLIAMS M J, et al. Seismic-to-simulation for unconventional reservoir development[C]//Paper presented at the SPE Reservoir Characterization and Simulation Conference and Exhibition. Abu Dhabi, UAE: Society of Petro-leum Engineers, 2011. [45] OLORODE O M, FREEMAN C M, MORIDIS G J, et al. High-resolution numerical modeling of complex and irregular fracture patterns in shale gas and tight gas reservoirs[C]//Paper pre-sented at the SPE Latin America and Caribbean Petroleum Engineering Conference. Mexico City, Mexico: Society of Petroleum Engineers, 2012. [46] WANG Yuhang, SHAHVALI M. Discrete fracture modeling using Centroidal Voronoi grid for simulation of shale gas plays with coupled nonlinear physics[J]. Fuel, 2016, 163: 65-73. [47] SUN Jianlei, SCHECHTER D, HUANG Chungkan. Grid-sensitivity analysis and comparison between unstructured perpendicular bisector and structured tartan/local-grid-refinement grids for hydraulically fractured horizontal wells in Eagle Ford Formation with complicated natural fractures[J]. SPE Journal, 2016, 21(6): 2260-2275. [48] SUN Jianlei, SCHECHTER D S. Optimization-based unstructured meshing algorithms for simulation of hydraulically and naturally fractured reservoirs with variable distribution of fracture aperture, spacing, length, and strike[J]. SPE Reservoir Evaluation & Engineering, 2015, 18(4): 463-480. [49] NIU Geng, SUN Jianlei, PARSEGOV S, et al. Integration of core analysis, pumping schedule and microseismicity to reduce uncertainties of production performance of complex fracture networks for multi-stage hydraulically fractured reservoirs[C]//Paper presented at the SPE Eastern Regional Meeting. Lexington, Kentucky, USA: Society of Petroleum Engineers, 2017. [50] MURALIDHARAN V, CHAKRAVARTHY D, PUTRA E, et al. Investigating fracture aperture distributions under various stress conditions using X-ray CT scanner[C]//Canadian International Petroleum Conference. Calgary, Alberta, Canada: Petroleum Society of CIM, Calgary, AB (Canada), 2004. [51] KIM T, PUTRA E, SCHECHTER D. Analyzing tensleep natural fracture properties using X-ray CT scanner[J]. Archives of Mining Sciences, 2007, 52(1): 3-20. -
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