页岩气开采中的若干力学前沿问题

页岩气的开采涉及破裂和收集输运两个关键过程.如何实现2000,m以下、复杂地应力作用下、多相复杂介质组分的页岩层内网状裂纹的形成,同时将孔洞、缝隙中的游离、吸附气体进行高效收集,涉及到诸多的核心力学问题.这一工程过程涵盖了力学前沿研究的诸多领域:介质和裂纹从纳米尺度到千米尺度的空间跨越,游离、吸附气体输运过程中微秒以下的时间尺度事件到历经数年开采的时间尺度跨越,不同尺度上流体固体的相互作用,以及压裂过程中通过监测信息反演内部破坏状态等.针对近年来我们国家页岩气勘探开发工作所取得的成就及后续发展中面临的前沿力学问题,在综合介绍页岩气藏的基本特征和开发技术的基础上,以页岩气开采中的若干力学前沿问题为主线,从页岩力学性质及其表征方法、页岩气藏实验模拟技术、页岩气微观流动机制及流固耦合特征、水力压裂过程数值模拟方法、水力压裂过程微地震监测技术、高效环保的无水压裂技术等6个方面的最新研究进展进行了总结和展望,结合页岩气藏开发的工程实践, 深入探究了其中力学关键问题,以期对从事页岩气领域的开发和研究的从业人员提供理论基础, 同时,该方面的内容对力学学科、尤其是岩土力学领域的科研工作也具有重要指导价值. 

Mechanical frontiers in shale-gas development

The development ofshale gas involves two critical processes including fracturing andtransportation. To realize reticular fractures in the shale layerof multi-phase under more than 2000 m subjected to complexgeo-stress and to collect the free and adsorbed gases encapsulatedin the layer, we face many key mechanical challenges to beaddressed. There are several cut-on-edge research topicsassociated with shale gas development: the huge span in structuralsize and fracture eveents from nanoscale to even severalkilometers, free and adsorbed gas transporting at temperal scalesfrom microseconds to the life-long mining of a shale-gas well, thefluid-solid interaction at different time and length scales, andthe in-situ monitoring on internal damage states duringfracturing. In view of the achievements in shale-gas explorationand the mechanical research frontiers for subsequent development,we give a comprehensive review on the basic characteristics anddevelopment techniques of shale-gas reservoirs. We cover in thisreview six aspects of the latest research progress, the mechanicalproperties of shales and their characterization, shale gasreservoir experimental techniques, shale gas micro-flow mechanismand fluid-solid coupling characteristics, numerical simulation ofhydraulic fracturing process, micro-seismic monitoring technologyof hydraulic fracturing process and high-efficiency andenvironmentally friendly waterless fracturing technology.Combining with the engineering practice of shale-gas reservoirdevelopment, the key issues of mechanics are presented, to providea theoretical basis for the practitioners engaged in thedevelopment and research of shale-gas field. We suspect that theprogress summarized here may help guide general research inmechanics, especially in geotechnical mechanics.