储层非均质性和各向异性对水力压裂裂纹扩展的影响
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摘要
针对页岩储层非均质性及各向异性影响水力压裂裂纹扩展规律的问题,利用数字图像处理方法建立反映页岩储层断面的非均质几何模型,基于页岩各向异性力学实验,建立非均质各向异性损伤模型,继而开展非均质各向异性页岩水力压裂数值模拟,得出了层理方位、地应力差以及层理面法向强度对页岩水力压裂裂纹扩展的影响规律。结果表明:随着层理与最大水平地应力间夹角、地应力差以及层理弱面强度的减小,裂纹遇层理时更易转向层理扩展;裂纹在层理面内的扩展速度随层理倾角和层理强度的减小而增加;若水平最大地应力不变,随着地应力差的减小,裂纹在储层基质和层理面内的扩展速度减小。研究成果为水力压裂开采页岩气提供了理论基础,对优化压裂设计方案、提高页岩气储层改造效率具有一定的指导意义。
In order to study the hydraulic fracturing crack propagation under various reservoir heterogeneity and anisotropy,digital image processing was used to establish the heterogeneous geometric model to characterize the shale reservoir section. A heterogeneous anisotropic damage model was established on the basis of the anisotropic mechanic shale experiment test data. The numerical simulation of hydraulic fracturing with heterogeneous anisotropic shale was carried out to identify the hydraulic fracturing crack propagation patterns under various bedding orientation,geo-stress difference and the normal strength of bedding plane. Result indicates that the crack is more likely to divert and propagate along the bedding with the decreases of the angle between bedding and maximum horizontal geo-stress,geo-stress difference and the strength of weak bedding plane. The crack propagating rate within the bedding plane increases with the decreases of bedding angle and bedding strength. The crack propagating rates within the reservoir matrix and bedding plane decrease with the decrease of geo-stress difference under the constant horizontal maximum geo-stress. This research could provide certain theoretical basis for hydraulic fracturing in the shale gas production and could also provide certain guidance for the hydraulic fracturing program optimization and shale gas reservoir stimulation efficiency.
In order to study the hydraulic fracturing crack propagation under various reservoir heterogeneity and anisotropy,digital image processing was used to establish the heterogeneous geometric model to characterize the shale reservoir section. A heterogeneous anisotropic damage model was established on the basis of the anisotropic mechanic shale experiment test data. The numerical simulation of hydraulic fracturing with heterogeneous anisotropic shale was carried out to identify the hydraulic fracturing crack propagation patterns under various bedding orientation,geo-stress difference and the normal strength of bedding plane. Result indicates that the crack is more likely to divert and propagate along the bedding with the decreases of the angle between bedding and maximum horizontal geo-stress,geo-stress difference and the strength of weak bedding plane. The crack propagating rate within the bedding plane increases with the decreases of bedding angle and bedding strength. The crack propagating rates within the reservoir matrix and bedding plane decrease with the decrease of geo-stress difference under the constant horizontal maximum geo-stress. This research could provide certain theoretical basis for hydraulic fracturing in the shale gas production and could also provide certain guidance for the hydraulic fracturing program optimization and shale gas reservoir stimulation efficiency.
引文
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[5]王世谦.页岩气资源开采现状、问题与前景[J].天然气工业,2017,37(6):115-130.
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[7]赵金洲,任岚,胡永全,等.裂缝性地层水力裂缝张性起裂压力分析[J].岩石力学与工程学报,2013,32(增刊1):2855-2862.
[8]陈勉,葛洪魁,赵金洲,等.页岩油气高效开发的关键基础理论与挑战[J].石油钻探技术,2015,43(5):7-14.
[9]金衍,陈勉,张旭东.天然裂缝地层斜井水力裂缝起裂压力模型研究[J].石油学报,2006,27(5):124-126.
[10]何岩峰,赵虹宇,窦祥骥,等.考虑应力敏感的页岩储层纳米孔隙渗透率计算模型[J].大庆石油地质与开发,2018,37(6):151-157.
[11]刘向君,丁乙,罗平亚,等.天然裂缝对水力裂缝延伸的影响研究[J].特种油气藏,2018,25(2):148-153.
[12]李玉梅,柳贡慧,李军,等.页岩储层各向异性对裂缝起裂压力的影响[J].特种油气藏,2014,21(6):133-137.