Evaluation method and application of fracturing effect based on dynamic permeability change of coal reservoir hydraulic fracturing
-
摘要: 压裂施工曲线是反映压裂效果的重要依据,而压裂阶段储层渗透率的动态变化能够更直观地反映造缝效果。借鉴试井渗透率测试原理,建立一种压裂阶段储层动态渗透率定量评价方法,并将该方法应用到准南某区块2口煤层气井水力压裂效果评价中,获得压裂阶段储层动态渗透率曲线;同时采用G函数对压裂效果进一步评价。结果表明:动态渗透率曲线所反映压裂效果与G函数分析和基于排量、井底流压关系的评价结果吻合较好,能够反映储层内裂缝开启、延伸效果;其中,CMG-01井通过实施煤储层与围岩大规模缝网改造,压裂阶段储层渗透率最高达到2.5 μm2,造缝效果良好;而CBM-02井实施煤储层常规水力压裂,储层渗透率保持在1.8 μm2之下,显示出煤储层常规水力压裂与煤储层−围岩大规模缝网改造的差异性。动态渗透率定量评价方法弥补前期压裂改造效果缺乏量化评价的不足,为煤层气/煤系气储层水力压裂工艺的优化提供依据。Abstract: The fracturing construction curve is considered to be an important basis for reflecting the fracturing effect, while the dynamic change of reservoir permeability in the fracturing stage can more intuitively reflect the effect of fracture formation. In this paper, a quantitative evaluation method for reservoir dynamic permeability in fracturing stage was established based on the principle of well testing. Then, the method was applied to evaluate the fracturing effect of two coalbed methane (CBM) wells in a block in southern Junggar Basin, and the dynamic permeability curve of reservoir during fracturing stage is obtained. Meanwhile, the G-function method was used to further evaluate the fracturing effect. The results show that the fracturing effect reflected by the dynamic permeability curve is consistent with the G-function analysis and the evaluation results based on the relationship between displacement and bottom hole pressure, which can reflect the opening and extension effects of fractures in the reservoir. Large-scale fracture network transformation of coal reservoirs and surrounding rocks was implemented in Well CMG-01, and the reservoir permeability in the fracturing stage was up to 2.5 μm2, showing a good fracturing effect. While the reservoir permeability of CBM-02 Well was kept below 1.8 μm2 after conventional hydraulic fracturing was performed in the coal reservoir. There are significant differences between conventional hydraulic fracturing of coal reservoirs and large-scale fracture network reconstruction of coal reservoirs and surrounding rocks. The formation of the quantitative evaluation method for reservoir dynamic permeability in fracturing stage can make up for the lack of quantitative evaluation of the fracturing effect, which provides a basis for optimizing hydraulic fracturing technologies of CBM or coal measure gas wells.
-
表 1 CMG-01井和CBM-02井改造情况
Table 1 Stimulation conditions of CMG-01 well and CBM-02 well
参数 CMG-01井 CBM-02井 改造层位 煤储层及其围岩 煤储层 压裂方式 大规模缝网改造 常规水力压裂 最高排量/
(m3·min−1)13 11 压裂液
总量/m31 640,1 500 1 220 支撑剂 16~30目,20~40目,40~70目 16~30目,20~40目 压裂液类型 活性水(清水+1%KCl) 活性水(清水+1.5%KCl) 注:16~30目对应600~1 180 μm,20~40目对应425~850 μm,40~70目对应212~425 μm,下同。 表 2 CMG-01井渗透率计算数据
Table 2 Permeability calculation data of CMG-01 well
序号 排量
/(m3·min−1)ln*t1 ln*t2 初始井底
流压/MPa阶段末井底
流压/MPa斜率mp 渗透率/μm2 1 12.86 1.609 2.079 19.50 19.75 1.56 1.374 2 13.24 1.098 1.945 19.67 17.92 0.95 2.594 3 13.26 1.791 2.079 19.11 18.79 1.10 2.241 4 13.02 0.693 1.609 20.68 19.79 0.96 2.173 5 13.02 1.098 1.386 23.82 24.54 2.49 0.999 6 13.24 0.693 1.098 31.24 32.54 3.21 0.674 7 13.19 1.098 1.609 26.08 26.67 1.14 2.048 注:t1、t2分别为压裂初始时间和结束时间,min;*t1=t1/min,*t2=t2/min。 表 3 CBM-02井渗透率计算数据
Table 3 Permeability calculation data of CBM-02 well
序号 排量
/(m3·min−1)ln*t1 ln*t2 初始井底
流压/MPa阶段末井底流压/MPa 斜率mp/MPa 渗透率/μm2 1 10.14 1.098 1.386 20.16 21.58 1.54 0.426 2 11.14 0.693 1.386 19.54 19.88 0.48 1.738 3 11.26 0.693 1.098 17.89 18.68 1.93 0.438 4 11.37 0 1.386 18.93 18.01 0.66 1.316 5 4.38 0.693 1.098 15.88 15.10 1.91 0.333 6 11.07 0.693 1.386 15.69 16.01 0.46 1.816 7 11.25 0 0.693 14.71 15.40 1.00 0.860 8 11.42 0.693 1.609 14.88 13.77 0.68 1.267 -
[1] 路艳军,杨兆中,SHELEPOV V V,等. 煤层气储层压裂现状及展望[J]. 煤炭科学技术,2017,45(6):73−84. LU Yanjun,YANG Zhaozhong,SHELEPOV V V,et al. Status and prospects of coalbed methane reservoir fracturing[J]. Coal Science and Technology,2017,45(6):73−84. [2] 王绪性,仲冠宇,郭布民,等. 沁水盆地南部3号煤压裂曲线特征及施工建议[J]. 煤田地质与勘探,2016,44(3):36−39. WANG Xuxing,ZHONG Guanyu,GUO Bumin,et al. Characteristics of fracturing curve of seam No. 3 in south of Qinshui Basin and suggestion about operation[J]. Coal Geology & Exploration,2016,44(3):36−39.. doi: 10.3969/j.issn.1001-1986.2016.03.007 [3] 张聪,李梦溪,王立龙,等. 沁水盆地南部樊庄区块煤层气井增产措施与实践[J]. 天然气工业,2011,31(11):26−29. ZHANG Cong,LI Mengxi,WANG Lilong,et al. EOR measures for CBM gas wells and their practices in the Fanzhuang block,southern Qinshui Basin[J]. Natural Gas Industry,2011,31(11):26−29.. doi: 10.3787/j.issn.1000-0976.2011.11.007 [4] 徐刚,彭苏萍,邓绪彪. 煤层气井水力压裂压力曲线分析模型及应用[J]. 中国矿业大学学报,2011,40(2):173−178. XU Gang,PENG Suping,DENG Xubiao. Hydraulic fracturing pressure curve analysis and its application to coalbed methane wells[J]. Journal of China University of Mining & Technology,2011,40(2):173−178. [5] 雷毅. 松软煤层井下水力压裂致裂机理及应用研究[D]. 北京: 煤炭科学研究总院, 2014.LEI Yi. Study on mechanism and application of hydraulic fracturing in soft seam underground mine[D]. Beijing: China Coal Research Institute, 2014. [6] 吴奇,胥云,王腾飞,等. 增产改造理念的重大变革:体积改造技术概论[J]. 天然气工业,2011,31(4):7−12. WU Qi,XU Yun,WANG Tengfei,et al. The revolution of reservoir stimulation:An introduction of volume fracturing[J]. Natural Gas Industry,2011,31(4):7−12.. doi: 10.3787/j.issn.1000-0976.2011.04.002 [7] 苏现波, 马耕, 宋金星, 等. 煤系气储层缝网改造技术及应用[M]. 北京: 科学出版社, 2017. [8] 吴奇,胥云,张守良,等. 非常规油气藏体积改造技术核心理论与优化设计关键[J]. 石油学报,2014,35(4):706−714. WU Qi,XU Yun,ZHANG Shouliang,et al. The core theories and key optimization designs of volume stimulation technology for unconventional reservoirs[J]. Acta Petrolei Sinica,2014,35(4):706−714.. doi: 10.7623/syxb201404011 [9] 陈作,薛承瑾,蒋廷学,等. 页岩气井体积压裂技术在我国的应用建议[J]. 天然气工业,2010,30(10):30−32. CHEN Zuo,XUE Chengjin,JIANG Tingxue,et al. Proposals for the application of fracturing by stimulated reservoir volume (SRV) in shale gas wells in China[J]. Natural Gas Industry,2010,30(10):30−32.. doi: 10.3787/j.issn.1000-0976.2010.10.007 [10] 薛海飞,朱光辉,王伟,等. 沁水盆地柿庄区块煤层气井压裂增产效果关键影响因素分析与实践[J]. 煤田地质与勘探,2019,47(4):76−81. XUE Haifei,ZHU Guanghui,WANG Wei,et al. Analysis and application of key influencing factors of CBM well fracturing effects in Shizhuang area,Qinshui Basin[J]. Coal Geology & Exploration,2019,47(4):76−81.. doi: 10.3969/j.issn.1001-1986.2019.04.012 [11] SU Xianbo,WANG Qian,LIN Haixiao,et al. A combined stimulation technology for coalbed methane wells:Part 1. Theory and technology[J]. Fuel,2018,233:592−603.. doi: 10.1016/j.fuel.2018.06.087 [12] SU Xianbo,WANG Qian,LIN Haixiao,et al. A combined stimulation technology for coalbed methane wells:Part 2. application[J]. Fuel,2018,233:539−551.. doi: 10.1016/j.fuel.2018.06.086 [13] 王乾. 淮北某区块煤层气井二次改造关键技术[D]. 焦作: 河南理工大学, 2017.WANG Qian. The key technologies of secondary stimulation for coalbed methane well in a block of Huaibei[D]. Jiaozuo: Henan Polytechnic University, 2017. [14] SUN Bin,JU Yiwen,LU Shuangfang,et al. Reconstruction evaluation method and application of coal measure three gases co–mining reservoirs in Linxing block,East Ordos Basin[J]. Advances in Geosciences,2020,10(2):85−99.. doi: 10.12677/AG.2020.102010 [15] CHONG K K, GRIESER B. A completions roadmap to shale–play development: A review of successful approaches toward shale–play stimulation in the last two decades[R]. Society of Petroleum Engineers, Beijing, SPE–130369, 2010. [16] 沈永星,冯增朝,周动,等. 天然裂缝对页岩储层水力裂缝扩展影响数值模拟研究[J]. 煤炭科学技术,2021,49(8):195−202. SHEN Yongxing,FENG Zengchao,ZHOU Dong,et al. Study on numerical simulation of effect on natural fractures to hydraulic fracture propagation in shale reservoirs[J]. Coal Science and Technology,2021,49(8):195−202. [17] 张晓娜,康永尚,姜杉钰,等. 沁水盆地柿庄区块3号煤层压裂曲线类型及其成因机制[J]. 煤炭学报,2017,42(增刊2):441−451. ZHANG Xiaona,KANG Yongshang,JIANG Shanyu,et al. Fracturing curve types and their formation mechanism of coal seam 3 in Shizhuang block,Qinshui Basin[J]. Journal of China Coal Society,2017,42(Sup.2):441−451. [18] 张永成,郝海金,李兵,等. 煤层气水平井微地震成像裂缝监测应用研究[J]. 煤田地质与勘探,2018,46(4):67−71. ZHANG Yongcheng,HAO Haijin,LI Bing,et al. Application of microseismic monitoring and imaging of fractures in horizontal CBM well[J]. Coal Geology & Exploration,2018,46(4):67−71.. doi: 10.3969/j.issn.1001-1986.2018.04.011 [19] 毛国扬,胡永全,赵金洲,等. 裂缝性油藏压后压降分析[J]. 断块油气田,2009,16(1):69−71. MAO Guoyang,HU Yongquan,ZHAO Jinzhou,et al. Pressure decline curve analysis of naturally fractured reservoir after being fractured[J]. Fault Block Oil & Gas Field,2009,16(1):69−71. [20] BARREE R D, MISKIMINS J L, GILBERT J V. Diagnostic fracture injection tests: Common mistakes, misfires, and misdiagnoses[J]. SPE 169539, 2014. [21] 李传亮. 油藏工程原理(第二版)[M]. 北京: 石油工业出版社, 2011. [22] 王聚团,刘银山,黄志明,等. G函数压降分析方法优化及应用[J]. 非常规油气,2020,7(4):81−84. WANG Jutuan,LIU Yinshan,HUANG Zhiming,et al. Pressure drop analysis methods for small–scale fracturing[J]. Unconventional Oil & Gas,2020,7(4):81−84. [23] 王兴文. 裂缝性油藏压裂压力递减分析研究与应用[D]. 成都: 西南石油学院, 2004.WANG Xingwen. Research and application of fracturing pressure decline analysis in fractured reservoirs[D]. Chengdu: Southwest Petroleum Institute, 2004. [24] NOLTE K G. Determination of fracture parameters from fracturing pressure decline[R]. SPE 8341, 1979. [25] NOLTE K G, MANIERE J L, OWENS K A. After–closure analysis of fracture calibration tests[R]. SPE 38676, 1997. [26] 赵文,张遂安,孙志宇,等. 基于G函数曲线分析的压后裂缝复杂性评估研究[J]. 科学技术与工程,2016,16(33):1671−1815. ZHAO Wen,ZHANG Suian,SUN Zhiyu,et al. Evaluative research for the fracture complexity after fracturing based on the G–function curves analysis[J]. Science Technology and Engineering,2016,16(33):1671−1815. [27] 毛国扬,杨怀成,张文正. 裂缝性储层压降分析方法及其应用[J]. 石油天然气学报,2011,33(7):116−118. MAO Guoyang,YANG Huaicheng,ZHANG Wenzheng. Pressure drow down analysis method and its application in fractured reservoir[J]. Journal of Oil and Gas Technology,2011,33(7):116−118.. doi: 10.3969/j.issn.1000-9752.2011.07.027