硬脆性泥页岩水化裂缝发展的CT成像与机理
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摘要
硬脆性泥页岩地层井壁失稳问题是一个十分复杂的难题。外来流体侵入后,岩石内部将会产生一系列的微观物理化学变化而影响地层的稳定性。采用CT成像技术,微观揭示硬脆性泥页岩水化过程中裂缝的发展规律及其对岩石的破坏,并结合扫描电镜等测试手段,分析其机理和对井壁失稳的影响,进而制定出井壁稳定技术对策,为硬脆性泥页岩井壁稳定性研究提供一种新的思路。结果表明,硬脆性泥页岩具有较显著的毛细管效应,岩石矿物颗粒间微孔缝自吸水后产生较强的水化作用,促使次生微裂纹的产生、扩展与连通,微裂纹不断发展成裂缝直至贯通,岩石发生宏观破坏。自吸水化产生次生裂缝破坏是硬脆性泥页岩地层井壁失稳的主要原因之一。强化封堵、控制滤失量和降低滤液表面张力是防止硬脆性泥页岩地层自吸水化破坏的有效措施。
The borehole wall instability of hard-brittle shale formations is a very complex problem because after the invasion of foreign fluids,rocks will have a series of internal microscopic physical and chemical changes that affect the stability of formations.Here we proposed a new approach to studying the borehole wall instability of hard-brittle shale formations,which can microcosmically reveal the development law of cracks and the damage to rocks during a hydration process of hard-brittle shales by means of CT imaging technology,analyze its mechanism of and effects on the borehole wall instability with a combination of scanning electron microscope and other instrumentations,and then set down a practicable countermeasure for wall stabilization.The results show that hard-brittle shale has a notable capillary effect,by which spontaneous imbibition of micropores among particles of rock matrix will result in a strong hydration that promotes the generation,expansion and connectivity of secondary micropores.The continuous development of micropores into cracks till penetrated fracturing through rocks will bring about macroscopic damage to rocks.Therefore,one of the major causes that lead to the instability of brittle shale formations is the damage of secondary micropores generated from the hydration by spontaneous imbibition.Thus,intensifying plugging,controlling filter loss and reducing the surface tension of filtrate are effective measures to prevent hard-brittle shale formations from the hydration damage by spontaneous imbibition.
The borehole wall instability of hard-brittle shale formations is a very complex problem because after the invasion of foreign fluids,rocks will have a series of internal microscopic physical and chemical changes that affect the stability of formations.Here we proposed a new approach to studying the borehole wall instability of hard-brittle shale formations,which can microcosmically reveal the development law of cracks and the damage to rocks during a hydration process of hard-brittle shales by means of CT imaging technology,analyze its mechanism of and effects on the borehole wall instability with a combination of scanning electron microscope and other instrumentations,and then set down a practicable countermeasure for wall stabilization.The results show that hard-brittle shale has a notable capillary effect,by which spontaneous imbibition of micropores among particles of rock matrix will result in a strong hydration that promotes the generation,expansion and connectivity of secondary micropores.The continuous development of micropores into cracks till penetrated fracturing through rocks will bring about macroscopic damage to rocks.Therefore,one of the major causes that lead to the instability of brittle shale formations is the damage of secondary micropores generated from the hydration by spontaneous imbibition.Thus,intensifying plugging,controlling filter loss and reducing the surface tension of filtrate are effective measures to prevent hard-brittle shale formations from the hydration damage by spontaneous imbibition.
引文
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[12]邓虎,孟英峰,陈丽萍,等.硬脆性泥页岩水化稳定性研究[J].天然气工业,2006,26(2):73-76.Deng Hu,Meng Yingfeng,Chen Liping,et al.Study on stability ofbrittle shale hydration[J].Natural Gas Industry,2006,26(2):73-76.
[13]邱正松,徐加放,吕开河,等.“多元协同”稳定井壁新理论[J].石油学报,2007,28(2):117-119.Qiu Zhengsong,Xu Jiafang,LüKaihe,et al.A multivariate coop-eration principle for well-bore stabilization[J].Acta Petrolei Sini-ca,2007,28(2):117-119.
[2]赵峰,唐洪明,孟英峰,等.微观地质特征对硬脆性泥页岩井壁稳定性影响与对策研究[J].钻采工艺,2007,30(6):16-18.Zhao Feng,Tang Hongming,Meng Yingfeng,et al.Study on theinfluence of microscopic geologic characteristics on wellbore sta-bility of brittle shale[J].Drilling&Production Technology,2007,30(6):16-18.
[3]刘玉石,白家祉,黄荣樽,等.硬脆性泥页岩井壁稳定问题研究[J].石油学报,1998,19(1):85-88.Liu Yushi,Bai Jiazhi,Huang Rongzun,et al.A study on stabilityof brittle shale wellbore[J].Acta Petrolei Sinica,1998,19(1):85-88.
[4]折海成,刘斌,华帅,等.裂缝吸水对泥页岩强度的影响[J].辽宁化工,2010,39(8):854-857.She Haicheng,Liu Bin,Hua Shuai,et al.Effect of hygroscope ofsplit on mud shale strength[J].Liaoning Chemical Industry,2010,39(8):854-857.
[5]丁卫华,仵彦卿,蒲毅彬,等.X射线岩石CT的历史与现状[J].地震地质,2003,25(3):467-474.Ding Weihua,Wu Yanqing,Pu Yibin,et al.History and presentsituation of X-ray computerized tomography(CT)of rocks[J].Seismology and Geology,2003,25(3):467-474.
[6]孙卫,史成恩,赵惊蛰,等.X-CT扫描成像技术在特低渗透储层微观孔隙结构及渗流机理研究中的应用[J].地质学报,2006,80(5):775-778.Sun Wei,Shi Cheng’en,Zhao Jingzhe,et al.Application of X-CTscanned image technique in the research of micro-pore textureand percolation mechanism in ultra-permeable oil field[J].ActaGeologica Sinica,2006,80(5):775-778.
[7]施伟军,陈荣林.一种研究油气储层裂缝的新方法——计算机层析(CT)法[J].石油实验地质,2001,23(3):344-347.Shi Weijun,Chen Ronglin.A new method to study the fissures inhydrocarbon reservoirs:computer asistrd tomography(CT)[J].Petroleum Geology&Experiment,2001,23(3):344-347.
[8]葛修润,任建喜,蒲毅彬.岩石疲劳损伤扩展规律CT细观分析初探[J].岩土工程学报,2001,23(2):191-195.Ge Xiurun,Ren Jianxi,Pu Yibin.Preliminary analysis on rock fa-tigue damage law by X-ray CT[J].Chinese Journal of Geotech-nical Engineering,2001,23(2):191-195.
[9]李果,张诗通.用石英玻璃模拟低渗砂岩毛细管自吸效应的研究[J].重庆科技学院学报:自然科学版,2010,12(3):1-3.Li Guo,Zhang Shitong.Self-absorption effect simulation of capil-lary in low-permeability Sandstone with quartz glass[J].Journalof Chongqing University of Science and Technology:Natural Sci-ences Edition,2010,12(3):1-3.
[10]刘厚彬,孟英峰,李皋,等.泥页岩水化作用对岩石强度的影响[J].钻采工艺,2010,33(6):18-20.Liu Houbin,Meng Yingfeng,Li Gao,et al.Theoretical simulationand experimental evaluation of the effect of hydration on theshale rock strength[J].Drilling&Production Technology,2010,33(6):18-20.
[11]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):2724-2728.Mao Haijun,Guo Yintong,Wang Guangjin,et al.Evaluation ofimpact of clay mineral fabrics on hydration process[J].Rock andSoil Mechanics,2010,31(9):2724-2728.
[12]邓虎,孟英峰,陈丽萍,等.硬脆性泥页岩水化稳定性研究[J].天然气工业,2006,26(2):73-76.Deng Hu,Meng Yingfeng,Chen Liping,et al.Study on stability ofbrittle shale hydration[J].Natural Gas Industry,2006,26(2):73-76.
[13]邱正松,徐加放,吕开河,等.“多元协同”稳定井壁新理论[J].石油学报,2007,28(2):117-119.Qiu Zhengsong,Xu Jiafang,LüKaihe,et al.A multivariate coop-eration principle for well-bore stabilization[J].Acta Petrolei Sini-ca,2007,28(2):117-119.
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