Investigation of the hydrate reservoir production under different depressurization modes

Abstract

Large reserves of natural gas hydrates exist, and the depressurization method has the greatest potential for gas hydrate reservoir recovery. Currently, the most commonly adopted depressurization simulation method is a constant bottom-hole pressure production scheme. This study proposes a new depressurization mode with decreasing bottom-hole pressure. The production characteristic was numerically investigated using this method. The results show the following: (1) As the depressurization exponent (n) decreases, the development effect improves, and production indexes including cumulative gas production/dissociation and gas-water ratio increase. However, the reservoir energy consumption is higher and the hydrate reformation is more severe. (2) Compared to the proposed depressurization mode, the hydrate production index of the constant bottom-hole pressure production (n?=?0) is better. However, the hydrate reservoir energy consumption is higher and the hydrate reformation is more severe using constant bottom-hole pressure production. (3) To achieve a balance between production and reservoir energy consumption during depressurization production, the bottom-hole pressure should be controlled by selecting a suitable depressurization exponent between n_min and n_max, which can be determined through numerical simulations.     

Experimental Study on Friction Coefficient Between Concrete and the Top Surface of Rubble Mound Foundation

Experimental studies on the friction coefficient between concrete and the top surface of a rubble mound foundation in China are reviewed. Through comparison of different test results, the development of this research is comprehensively analyzed. An experiment is carried out in the condition similar to prototype. The process curve of friction coefficient with the test block sliding is analyzed and a standard for determination of the friction coetfficient is defined. The variation features of the friction coefficient are analyzed on the basis of the present experimental results and other studies in China. It is shown that the friction coettfficient between concrete and the top surface of a rubble mound foundation decreases with the increase of the foundation pressure, and the friction coettqcient for a very fine leveling bed is smaller than that for a fine leveling bed.     

复合酶法制备鯷鱼活性寡肽的研究

探讨了用复合酶法制备鱼是鱼活性寡肽及其氨基酸组成和相对分子质量分布情况。应用正交试验法研究了酶量、酶解温度、酶解时间对鱼是鱼蛋白质水解度和酶解液苦味的影响。结果表明,最佳酶解作用条件是:酶量为100u/mL;酶解温度为50℃;酶解时间为4h。此时的酶解液苦味较低,水解度可达62.81%。应用氨基酸分析仪和凝胶排阻高效液相色谱分析了该寡肽的氨基酸组成和相对分子质量的分布范围,其十肽以下的小肽占67.77%,氨基酸组成平衡,必需氨基酸含量丰富。鱼是鱼活性寡肽有望成为保健食品、医药等领域的新型高品质原料。     

REE distribution in water-sediment interface system at deep ocean floor

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A higher-order σ-coordinate non-hydrostatic model for nonlinear surface waves

A higher-order non-hydrostatic model in a σ-coordinate system is developed. The model uses an implicit finite difference scheme on a staggered grid to simultaneously solve the unsteady Navier-Stokes equations (NSE) with the free-surface boundary conditions. An integral method is applied to resolve the top-layer non-hydrostatic pressure, allowing for accurately resolving free-surface wave propagation. In contrast to the previous work, a higher-order spatial discretization is utilized to approximate the large horizontal pressure gradient due to steep surface waves or rapidly varying topographies. An efficient direct solver is developed to solve the resulting block hepta-diagonal matrix system. Accuracy of the new model is validated by linear and nonlinear standing waves and progressive waves. The model is then used to examine freak (extreme) waves. Features of downshifting focusing location and wave asymmetry characteristics are predicted on the temporal and spatial domains of a freak wave.     

中国沿岸现代海平面变化及未来趋势分析

本文用线性回归分析方法，分１９８５年以前和１９９２年以前两个时段，对我国沿岸２５个验潮站近百年来的海平面资料进行了系统分析，计算了两个时段相对海平面变化的年速率和平均海面高度，论述了海平面变化的主要控制因素，并对未来海平面变化趋势进行了预测。计算结果表明，近百年来我国沿岸相对海平面在总体上不但持续上升，而且近年来上升速率普遍加快；根据海平面变化的主要控制因素变化趋向，预计到下世纪中叶前后，全球性海平面大幅度上升的可能性不大，我国沿岸区域性海乎面平均上升幅度不超过１５ｃｍ，不同岸段因地壳升降差异性大而有较大差别。     

Instrumentation and Numerical Analysis of Cylindrical Diaphragm Wall Movement During Deep Excavation at Coastal Area

The lateral deflection of a cylindrical diaphragm wall and the associated ground movement induced by deep excavation are analyzed by performing site instrumentations and numerical analyses in the coastal area of Korea. Wall lateral deflection, rebar stress, and pore water pressure were measured and analyzed in eight directions. Variations of soil properties with the decrease of confining pressure are compared by performing various in situ tests before ad after excavation. To calculate the wall lateral deflection accurately, the effects of small strain nonlinearity, confining pressure, and the hysteresis loading/unloading loop developed during excavation are considered in the proposed numerical analysis. By comparing numerical results with measured ones, the importances of considering small strain nonlinearity and confining pressure reduction in the nonlinear (FEM) are emphasized. Also, the effects of wall stiffness on the performance of cylindrical diaphragm walls are studied for future similar excavation in the coastal area.     

高精度CTD剖面仪研制过程中的专用设备

本文介绍了“油水分离压力罐”的主要理论依据及该设备采用的特殊的机械结构，实践证明，利用该设备实现了在实验室条件下，模拟深海重力场检测CTD剖面仪中的某些关键传感器的目的。     

旧路改建高速公路中地基强夯效应测试与工艺参数分析

旧路改建高速公路遇到的最主要的问题是地基的不均匀沉降。数值分析表明,对新的天然地基进行处理是解决这一问题的关键。强夯是加固地基的一种有效措施,为了对强夯工艺参数进行优化研究,对夯锤冲击地面过程中产生的动孔隙水压力、动土应力以及夯后超静孔隙水压力的消散过程进行了跟踪测试与分析。结果表明,对以风化料为主的地基,最大夯击数不宜超过4击,而且铺底夯完成2d后就可进行满夯。     

智能全站仪在大型压力容器焊接变形监测中的应用

在大型压力容器的部件焊接过程中,由于预热、焊接等工艺流程会导致各部件产生变形,从而引起部件之间的位置关系产生变化。为保证压力容器成品满足设计要求,必须在制造过程中实施变形监测,依据变形数据适当调整焊接工艺流程,控制变形量。提出采用智能全站仪配以自动变形监测软件对大型压力容器焊接变形进行实时监测,并应用于生产实践中,监测结果表明该方法自动化程度高、实时性好,能同时给出位置和姿态变形数据。