致密砂岩水压瞬态致裂液化格子波尔兹曼及有限元数值研究

Application of Lattice Boltzmann and Finite Element Fluid-solid Coupled Modeling to Tight Sandstone Transient Hydrofracturing-liquefaction under Earthquake Wave

水压瞬态致裂液化在地应力测量、地震破坏评估和机理研究、油气(天然气、页岩气)及地热资源开发等地学领域都具有重要的理论和应用价值。自20世纪60年代至今在理论和实际应用方面取得了一些奠基性和开创性成果,但鉴于问题复杂性,瞬态致裂液化机理至今尚不清楚。本研究应用格子波尔兹曼及有限元多孔介质流固耦合物理模型,对地震波载荷作用下致密砂岩水压瞬态致裂液化过程进行数值模拟研究。首先,以鄂尔多斯盆地某油田延长组致密砂岩为例,利用X射线CT断层成像技术,应用基于量子力学第一性原理格子波尔兹曼方法,建立致密砂岩数字岩芯模型。进而,推导格子波尔兹曼及有限元多孔介质流固耦合数值模型公式,建立致密砂岩水压致裂液化物理模型。最后,应用地震波载荷边界和初始条件,模拟瞬态致裂液化流固耦合过程,讨论了地震波载荷幅值、频率及作用时间对致密砂岩孔隙结构(孔隙度大小及连通性)、致密砂岩破裂最大主应力之间关系,得到了地震波作用下致密砂岩致裂液化准则。

Hydrofracturing-liquefaction mechanism is the basic theory for understanding the in-situ stress measurement,the petroleum-gas （nature gas and shale gas）-geothermic development,and earthquake damage evaluation and mechanism study.Due to the complexity and challenge of this issue,mechanism of dynamic hydrofracturing-liquefaction is still not clear,even if a lot of fundamental and landmark achievements had been obtained in this field since the 1960＇s.In this work,transient hydrofracturing-liquefaction of tight sandstone under earthquake wave was studied by using hybrid lattice Boltzmann and finite element fluid-solid coupled modeling on parallel GPU-CPU environment.First,the tight sandstone sample from the Ordos Basin Triassic formation was selected and different tomography resolution data was obtained by X-ray CT digital technology.Then,based on the D3Q27 lattice Boltzmann and finite element method,the fluid-solid coupled porous medium physical modeling was established,and the relatively hydrofracturing-liquefaction of tight sandstone was obtained for the first time.Last,the hydrofracturing-liquefaction process was simulated,and the relationship between the amplitude,frequency and time of the earthquake wave and the tight sandstone pore-network evolution,maximum tight sandstone fracturing-liquefaction stress criteria was explored.