含硫气井非达西渗流下的产能预测方法

含硫气藏在开发过程中,固态硫沉积将降低储层岩石孔隙度和渗透率,极大地破坏气井产能,此时常规气井产能计算模型已经不再适用,因此建立含硫气井产能预测模型十分重要。本文考虑硫元素在近井地带沉积引起的储层渗透率变化,将储层分为沉积区和非沉积区。基于渗流力学理论,建立了含硫气藏直井、水平井在平面径向非达西稳定渗流条件下的二次三项式产能方程。通过分析硫沉积、启动压力梯度、水平段长度对气井产能的影响,认为气井产能随硫沉积饱和度的增大而减小,无阻流量与启动压力梯度呈负相关关系,水平井段长度越长,产能越大。     

Assessing the influence of inflow turbulence on noise and performance of a tidal turbine using large eddy simulations

Large eddy simulations of a model scale tidal turbine encountering inflow turbulence have been performed. This has allowed both unsteady blade loading and hydrodynamic noise radiation to be predicted. The study is motivated by the need to assess environmental impact of tidal devices, in terms of their acoustic impact on marine species.Inflow turbulence was accounted for using a synthetic turbulence generator, with statistics chosen to represent the gross features of a typical tidal flow. The turbine is resolved in a fully unsteady manner using a sliding interface technique within the OpenFOAM^® libraries. Acoustic radiation is estimated using a compact source approximation of the Ffowcs Williams–Hawkings equation.It is observed that the long streamwise length scale of the inflow turbulence results in characteristic ‘humps’ in the turbine thrust and torque spectra. This effect is also evident in the far-field noise spectra. The acoustic sources on the blades are visualised in terms of sound pressure level and “Powell's source term”. These measures show that the dominant sources are concentrated at the blade leading edges towards the tip. This results from the high loading of the turbine blades, and causes the sound to radiate more akin to a monopole than a dipole.The full scale source level, obtained from scaling of the simulation results, is found to be lower than comparable measured data reported in the literature; this is attributed to additional sources not included in the present study. Based on the predicted source level, no physical impact on fish is expected.     

Improvement of the Parameterized Identification Model Using Quasi-Steady and Nonuniform Inflow Aerodynamic Model

Compared with those of a fixed-wing aircraft, the dynamics of a rotorcraft are significantly more complex. One of the major challenges in the design of an autonomous helicopter is the development of a flight dynamic model, which can be useful for simulation studies and for the design of control law and navigational aspects. There is always a trade-off from the accuracy of the mathematical model to the more simplified model required for a control design as far as the helicopter rotor/fuselage dynamics is concerned. Small-scale helicopters posses a higher bandwidth of dynamics; hence, models developed from the first principle alone do not fulfill the needs, and more-sophisticated mathematical models are thus required. The main objective of the present work is to improve the parameterized identification model by replacing it with a most-general flight dynamic model for a minihelicopter. This model includes the rotor blade flap dynamics, stabilizer bar dynamics, and vehicle dynamics, which will be applicable for a general maneuvering flight. A systematic study is undertaken to analyze the influence of inflow models and flap response on the helicopter trim. Stability of the minihelicopter is also analyzed; except for phugoid, all other modes are stable in hover and high forward flight conditions.     

安庆铜矿地下水渗流场的模拟

水力坡度较大的矿坑地下水渗流场的模拟一直是一个难点。在分析矿区水文地质条件的基础上，对矿坑附近渗流场采用基于达西定律的解析法进行模拟，而对矿坑外围则采用有限单元法进行模拟，再将两者巧妙地结合起来，从而完成了矿床地下水渗流场的模拟，取得了较好的效果。     

一种新的考虑应力敏感影响的三项式产能方程

低渗透气藏存在较强的应力敏感性,对大量岩石实验数据回归研究表明,幂函数渗透率应力敏感性经验方程相关性相对较好,但是利用该关系式来研究低渗透气藏气井产能的报道还较少。利用幂函数渗透率应力敏感性经验公式,综合考虑渗透率应力敏感效应、启动压力梯度、紊流效应和表皮系数,建立了一个新的适用于低渗透异常高压气井的三项式产能方程。不同参数组合情况下的气井流入动态曲线对比研究结果表明,应力敏感性、启动压力梯度和紊流效应对低渗透气藏气井产能的影响较大,在产能评价研究时必须予以考虑。     

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对比了Ｍｉｓｈｒａ＆．Ｃａｕｄｌｅ相关式、二次式和指数式三类无因次ＩＰＲ方程的处理方法、性能特点和无因次采气指数。重点讨论了二次式特征参数α的物理意义及其影响因素。利用陕８井的四点试井数据进行了实例分析，指出了经验相关式和统计参数对于单点产能测试的局限性。     

A neuro-fuzzy model for inflow forecasting of the Nile river at Aswan high dam

River flow forecasting is an essential procedure that is necessary for proper reservoir operation. Accurate forecasting results in good control of water availability, refined operation of reservoirs and improved hydropower generation. Therefore, it becomes crucial to develop forecasting models for river inflow. Several approaches have been proposed over the past few years based on stochastic modeling or artificial intelligence (AI) techniques. In this article, an adaptive neuro-fuzzy inference system (ANFIS) model is proposed to forecast the inflow for the Nile River at Aswan High Dam (AHD) on monthly basis. A major advantage of the fuzzy system is its ability to deal with imprecision and vagueness in inflow database. The ANFIS model divides the input space into fuzzy sub-spaces and maps the output using a set of linear functions. A historical database of monthly inflows at AHD recorded over the past 130 years is used to train the ANFIS model and test its performance. The performance of the ANFIS model is compared to a recently developed artificial neural networks (ANN) model. The results show that the ANFIS model was capable of providing higher inflow forecasting accuracy specially at extreme inflow events compared with that of the ANN model. It is concluded that the ANFIS model can be quite beneficial in water management of Lake Nasser reservoir at AHD.     

Effect of Covers for Soil and Water Conservation Using Tilting Flume

The effect of stone and vegetative covers was evaluated for soil and water conservation in a waterway on alfisols. Experiments were conducted on a hydraulic tilting flume under simulated flow (93 and 40 cm2?s?1) and slope (0.1, 1.0, 3.0, and 5.0%) conditions. The depth of soil was maintained at 0.35 m over a perforated bed to facilitate deep drainage. A comparative study of bare soil, stone cover (50%), and vegetative cover (50%) is made to evaluate soil loss, deep drainage, Manning’s roughness coefficient, and the Froude number. The study has revealed that stone cover is more effective than vegetative cover at lower discharge in reducing the flow velocity, and thereby soil erosion. Deep drainage has been reduced from lower to higher discharge for all the slopes with cover measures, including bare soil. It is found that cover measures are necessary beyond 3% slope in order to prevent rill erosion in alfisols.     

轻烃泵用双端面机械密封的改造设计

本文阐述并分析了轻烃泵用双端面机械密封的特点，提出了改进方法和设计依据。     

Mixing in Water Storage Tanks. I: No Buoyancy Effects

The results of extensive experiments on jet-induced mixing in water storage tanks are reported in two papers. The experiments were conducted on three styles of storage tanks using a newly developed three-dimensional laser-induced fluorescence (3DLIF) system that can measure the whole field of tracer concentrations in the tanks and its temporal evolution through the mixing process. Various inlet geometries were tested for each tank style. In this paper, the results of experiments with no buoyancy effects are given. The 3DLIF technique enabled complex flow patterns to be observed such as a donut-shaped dead zone that inhibited mixing in ground-level cylindrical tanks. Values of dimensionless mixing times are presented that enable comparisons of the mixing efficiency of different inlet configurations and allow prediction of mixing times in prototype tanks. For cylindrical tanks, the dimensionless mixing time increases with increasing depth-to-diameter ratio. Vertical nozzles at the bottom mixed most efficiently. If a single vertical nozzle is used, placing it near a sidewall is preferred. Mixing becomes somewhat more rapid as the number of nozzles increase. Mixing times for rectangular tanks are generally similar to cylindrical tanks. The use of a tube intended to enhance mixing actually inhibited mixing in standpipe tanks.