沁水盆地煤储层地层能量演化历史研究

煤储层地层弹性能包括煤基块弹性能、水体弹性能和气体弹性能。对沁水盆地煤储层地层能量的演化发展进行了综合分析,并以关键时刻——燕山中期为界,定量研究了储层弹性能量的地质演化规律,结果表明,煤层气成藏作用与地质历史过程中地层能量场演化息息相关,气藏随着能量系统的动态平衡、聚集散失而发展变化,既可以形成新的气藏,也可能破坏原有气藏,据此认为,评价和预测煤层气成藏的关键是研究区煤储层弹性能量场的演化过程。

基于两种数学模型的水力—机械系统小波动稳定分析

采用不考虑水体弹性的状态空间法和考虑水体弹性的非线性整体系统数值模拟法,比较了某水电站小波动过渡过程中的调压室波动情况和调节品质指标。结果表明,两种计算模型的计算结果基本吻合,前者可先分析系统小波动稳定性,再利用后者校核,共同优化调速器参数,以确保系统小波动的稳定。

水轮机调速系统的H_∞双回路鲁棒控制策略

建立了考虑水电站引水系统水锤效应的弹性水体水轮机模型,并据此构建了水轮机调速系统模型。针对水轮机调速系统具有参数不确定性、存在干扰等特点,运用H∞鲁棒控制理论,提出了水轮机调速系统H∞双回路鲁棒控制策略,以水门开度偏差为补偿信号构建了内环反馈回路,以发电机转速偏差为补偿信号构建了外环反馈回路。仿真结果验证了该控制策略的有效性,而且其时域性能指标明显优于传统比例–微分–积分(proportional integral derivative,PID)调节器控制效果。

煤储层弹性能及其对煤层气成藏的控制作用

煤层气成藏维系于其能量平衡系统,其核心是能量的有效传递及其地质选择过程.煤储层弹性能包括煤基块弹性能、水体弹性能和气体弹性能.在结合煤样力学实验的基础上,对不同弹性能进行了定量分析研究,并深入探讨了煤储层弹性能对煤层气成藏的控制作用,结果表明:当气藏无边水、底水时,在成藏初期阶段,储层的储气能力主要由煤基块弹性能控制,气体弹性能的影响力次之,水体弹性能影响最小.在成藏中后期阶段,储能主要受气体弹性能控制;当气藏有边水、底水时,初期阶段的储能主要以煤基块弹性能和气体弹性能为主,但是随着水体增大,水体弹性能的影响力增大.中后期阶段,还是以气体弹性能的影响为主,占中后期全部储能的80%以上.总之,煤层气藏在形成初期以储存煤基块弹性能为主,中后期以储存气体弹性能为主,整个过程中,水体越大,水体弹性能对成藏的影响越大.研究认为:煤储层弹性能越高,越有利于煤层气的富集成藏.其中,高的煤基块弹性能和气体弹性能,有利于气藏高产,而高的水体弹性能,则有利于气藏稳产.因此,评价煤层气成藏的关键是煤储层弹性能量.

Two-dimensional Numerical Simulation of an Elastic Wedge Water Entry by a Coupled FDM-FEM Method

Hydroelastic behavior of an elastic wedge impacting on calm water surface was investigated. A partitioned approach by coupling finite difference method （FDM） and finite element method （FEM） was developed to analyze the fluid structure interaction （FSI） problem. The FDM, in which the Constraint Interpolation Profile （CIP） method was applied, was used for solving the flow field in a fixed regular Cartesian grid system. Free surface was captured by the Tangent of Hyperbola for Interface Capturing with Slope Weighting （THINC/SW） scheme. The FEM was applied for calculating the structural deformation. A volume weighted method, which was based on the immersed boundary （IB） method, was adopted for coupling the FDM and the FEM together. An elastic wedge water entry problem was calculated by the coupled FDM-FEM method. Also a comparison between the current numerical results and the published results indicate that the coupled FDM-FEM method has reasonably good accuracy in predicting the impact force.

Mechanical Response of Saturated Geological Rock Mass under Tidal Force

In this paper, the mechanical response of saturated geological rock under tidal force is explored by poroelastic theory. First, we use the free energy formula of saturated rock under a tidal force to study the relationships of pore pressure with stress, and stress with strain. Then we analyze the relationship between rock strain and tidal potential by the equilibrium differential equations of saturated rock under tidal force. Finally, we derive the physical relationship between the two parameters （pore pressure and tidal mean stress） of saturated rock and tidal potential. The relationship shows that：pore pressure is directly proportional with tidal potential, but tidal mean stress of saturated rock is inversely proportional with tidal potential. The ratio coefficient is related not only to the Lame coefficients of rock skeletons, but also to the Blot modulus. By using this model to analyze observational well water level of C-18 well which locates in Huili, Sichuan Province, the well level response coefficient （D） was estimated. This way, we derive the Skempton coefficient （B）, the coefficient A and C which refer to the response coefficients of pore pressure and tidal stress to tidal potential respectively. Then we compare the differences among each coefficient in coupling and uncoupling conditions. It shows that for saturated rocks, the response of stress and pore pressure to earth tides is a product of coupling, and it is necessary to take into account the coupling effect when we study the mechanical response. The model will provide the basis not only for the study of mechanics and hydrodynamics of well-confined aquifer systems, and the mechanics of faulting under tidal force, but also for quantitative research of the triggering mechanism of tidal forces.

Analytic approximation to nonlinear hydroelastic waves traveling in a thin elastic plate floating on a fluid

An analytic approximation method known as the homotopy analysis method(HAM)is applied to study the nonlinear hydroelastic progressive waves traveling in an infinite elastic plate such as an ice sheet or a very large floating structure(VLFS)on the surface of deep water.A convergent analytical series solution for the plate deflection is derived by choosing the optimal convergencecontrol parameter.Based on the analytical solution the efects of diferent parameters are considered.We find that the plate deflection becomes lower with an increasing Young’s modulus of the plate.The displacement tends to be flattened at the crest and be sharpened at the trough as the thickness of the plate increases,and the larger density of the plate also causes analogous results.Furthermore,it is shown that the hydroelastic response of the plate is greatly afected by the high-amplitude incident wave.The results obtained can help enrich our understanding of the nonlinear hydroelastic response of an ice sheet or a VLFS on the water surface.