Fracture Extension Mechanism and Water Control Significance of Fractured Reservoir

doi:10.12068/j.issn.1005-3026.2021.05.020

Abstract

Abstract: Aiming at geological problems such as water inrush in fractured reservoirs triggered by hydraulic fractures. Firstly， according to the principle of elastic mechanics and fracture mechanics strength criterion， based on the geometric characteristics of reservoir primary fracture and the seepage law of fracturing fluid， the calculation model of fracture initiation pressure under vertical well condition is established. Secondly， considering the damage constitutive relationship of coal reservoir， the Dougill damage factor is combined with the fracture initiation pressure formula to further establish the extension pressure calculation model. Using the classic PKN model and the nonlinear pressure drop law of the net pressure in the fracture， an improved fracture propagation model is established. The model reveals the non-linear relationship between fracture length L and fracturing time t in fractured reservoirs， showing that the extension distance of fractures increases with time， but it increases rapidly in the early stage and basically stabilizes in the later stage. The calculation results of three test wells in the Encun block of Jiaozuo in northern Henan Province are in good agreement with the microseismic data of the adjacent block， which verifies the correctness of the theoretical model and provides reliable technical support for on-site fracturing parameter control and prevention of fracture water inrush.

Key words: vertical well; fault inrush; fractured pressure; extension pressure; fracture extension model

CLC Number:

TE375

WANG Zhi-rong， SONG Pei， CHEN Ling-xia， HU Kai. Fracture Extension Mechanism and Water Control Significance of Fractured Reservoir[J]. Journal of Northeastern University(Natural Science), 2021, 42(5): 741-747.

References

[1]胡向志，王志荣，张振伦.煤层气开发与“三软”矿区瓦斯抽采［M］.郑州:黄河水利出版社，2011:1-5(Hu Xiang-zhi，Wang Zhi-rong，Zhang Zhen-lun.Development of CBM & gas drainage in "three soft" mining area［M］.Zhengzhou:The Yellow River Water Conservancy Press，2011:1-5.)
[2]Adachi J，Siebrits E，Peirce A.Computer simulation of hydraulic fractures［J］.International Journal of Rock Mechanics and Mining Sciences， 2007，44:739-757.
[3]Wei Y，Economides M J.Transverse hydraulic fractures from a horizontal well［C］//SPE 94671 Presented at the 2005 SPE Annual Technical Conference and Exhibition.Dallas 2005.
[4]韩金轩，杨兆中，王会来，等.煤储层压裂液滤失计算模型［J］.煤炭学报，2014，39(sup2):441-446.(Han Jin-xuan，Yang Zhao-zhong，Wang Hui-lai，et al.Leak-off model of fracturing fluid in coal seam［J］.Journal of China Coal Society，2014，39(sup2):441－446.)
[5]张小东，张鹏，刘浩，等.高煤级煤储层水力压裂裂缝扩展模型研究［J］.中国矿业大学学报，2013，42(4):573-579.(Zhang Xiao-dong，Zhang Peng，Liu Hao，et al.Fracture extended model under hydraulic fracturing engineering for high rank coal reservoirs［J］.Journal of China University of Mining & Technology，2013，42(4):573-579.)
[6]张小东，张硕，杨艳磊，等.基于分形理论的煤储层水力压裂裂缝数值模拟［J］.天然气地球科学，2015，26(10):1992-1998.(Zhang Xiao-dong，Zhang Shuo，Yang Yan-lei，et al.Numerical simulation of fracture extending in coal seam under hydraulic fracturing engineering based on fractal theory［J］.Natural Gas Geoscience，2015，26(10):1992-1998.)
[7]李连崇，张潦源，黄波，等.薄互层储层水平井压裂裂缝延伸规律模拟分析［J］.地下空间与工程学报，2016，12(6):1577-1585.(Li Lian-chong，Zhang Liao-yuan，Huang Bo，et al.Numerical investigation on the propagation law of hydraulic fractures near horizontal wells in thin interbedded reservoir［J］.Chinese Journal of Underground Space and Engineering，2016，12(6):1577-1585.)
[8]谭鹏，金衍，侯冰，等.煤岩定向井水力裂缝起裂及非平面扩展实验［J］.石油勘探与开发，2017，44(3):439-445.(Tan Peng，Jin Yan，Hou Bing，et al.Experimental investigation on fracture initiation and non-planar propagation of hydraulic fractures in coal seams［J］.Petroleum Exploration and Development， 2017，44(3):439-445.)
[9]张鹏海，张子麟，李明，等.低渗储油层水力压裂裂缝延伸过程及成缝机理［J］.东北大学学报(自然科学版)，2019，40(5):745-749.(Zhang Peng-hai，Zhang Zi-lin，Li Ming，et al.Extension process and fracture mechanism of hydraulic fractures in low permeability reservoir［J］.Journal of Northeastern University(Natural Science)，2019，40(5):745-749.)
[10]贾奇锋，倪小明，赵永超，等.不同煤体结构煤的水力压裂裂缝延伸规律［J］.煤田地质与勘探，2019，47(2):51-57.(Jia Qi-feng，Ni Xiao-ming，Zhao Yong-chao，et al.Fracture extension law of hydraulic fracture in coal with different structure［J］.Coal Geology & Exploration，2019，47(2):51-57.)
[11]高柏，王广才，周来逊，等.华北型煤田岩溶水水文地球化学研究进展［J］.水文地质工程地质，2009，36(3):59-63.(Gao Bai，Wang Guang-cai，Zhou Lai-xun，et al.Advances in the study of hydrogeochemistry of karstic groundwater in coal mines in North China［J］.Hydrogeology & Engineering Geology，2009，36(3):56-63.)
[12]Wang Z R，Chen L X，Cheng C R，et al.Forecast of gas geological hazards for “three-soft” coal seams in gliding structural area［J］.Journal of China University of Mining and Technology， 2007，17(4):484-488.
[13]王志荣，韩中阳，李树凯，等.“三软”煤层注水压裂增透机理及瓦斯抽采施工参数确定［J］.天然气地球科学，2014，25(5):739-746.(Wang Zhi-rong，Han Zhong-yang，Li Shu-kai，et al.Mechanism of water-fracturing-induced permeability increment of “three soft” coal seam and construction parameters determination［J］. Natural Gas Geoscience，2014，25(5):739-746.)
[14]王志荣，贺平，郭志伟，等.水力压裂条件下“三软”煤层压裂渗透模型及应用［J］.天然气地球科学，2017，28(3):349-355.(Wang Zhi-rong，He Ping，Guo Zhi-wei，et al.The research on permeable model of hydraulic fracture and its application in the “three soft” coal seam［J］.Natural Gas Geoscience，2017，28(3):349-355.)
[15]张金才，尹尚先.页岩油气与煤层气开发的岩石力学与压裂关键技术［J］.煤炭学报，2014，39(8):1691-1699.(Zhang Jin-cai，Yin Shang-xian.Some technologies of rock mechanics applications and hydraulic fracturing in shale oil，shale gas and coalbed methane［J］.Journal of China Coal Society，2014，39(8):1691-1699.)
[16]秦绪英，陈有明，陆黄生.井中应力场的计算及其应用研究［J］.石油物探，2003(2):271-275.(Qin Xu-ying，Chen You-ming，Lu Huang-sheng.Calculation of broehole stress with full-wave acoustic logging data and its application［J］.Geophysical Prospecting for Petroleum，2003(2):271-275.)
[17]王志荣，贺平，郭志伟，等.考虑裂缝特性指标的煤层气“垂直井”起裂压力计算方法［J］.岩土力学，2018，39(sup1):369-377.(Wang Zhi-rong，He Ping，Guo Zhi-wei，et al.Calculation of initiation pressure of vertical well for coalbed methane considering crack characteristic index［J］.Rock and Soil Mechanics，2018，39(sup1):369-377.)
[18]陈蕴生，韩信，李宁，等.非贯通裂隙介质单轴受力条件下的损伤本构关系探讨［J］.岩石力学与工程学报，2005，24(sup2):5926-5931.(Chen Yun-sheng，Han Xin，Li Ning，et al.Discussion on damage constitutive relation of non-interpenertrated crack media under uniaxial stress［J］.Chinese Journal of Rock Mechanics and Engineering，2005，24(sup2):5926-5926.)
[19]王志荣，郭志伟，贺平，等.基于PKN分析的煤层气垂直井水力压裂时间计算模型［J］.河南理工大学学报(自然科学版)，2018，37(4):24-30.(Wang Zhi-rong，Guo Zhi-wei，He Ping，et al.Calculation model on hydraulic fracturing time in gas vertical well based on PKN analysis［J］.Journal of Henan Polytechnic University(Natural Science)，2018，37(4):24-30.)
[20]刘浩.高煤级煤储层水力压裂的裂缝预测模型及效果评价［D］.焦作:河南理工大学，2010.(Liu Hao.The prediction model and evaluation for hydraulical fracture of high rank coal reservoirs ［D］.Jiaozuo:Henan Polytechnic University，2010.)
[21]宋佳，卢渊，李永寿，等.煤岩压裂液动滤失实验研究［J］.油气藏评价与开发，2011，1(1):74-77.(Song Jia，Lu Yuan，Li Yong-shou，et al.Experiment research on fracture fluid dynamic filtration of coal rocks［J］.Reservoir Evaluation and Development，2011，1(1):74-77.)
[22]蔡美峰，何满潮，刘东燕.岩石力学与工程［M］.北京:科学出版社，2013:108-111.(Cai Mei-feng，He Man-chao，Liu Dong-yan.Rock mechanics and engineering［M］.Beijing:Science Press，2013:108-111.)