Non-Darcian Flow Toward a Finite-Diameter Vertical Well in a Confined Aquifer

Non-Darcian radial flow toward a finite-diameter,fully penetrating well in a confined aquifer was analyzed on the basis of the Izbash equation with consideration of the wellbore storage eflect.We derived semi-analytical solutions of drawdown by using the Boltzmann transform,and obtained approximate analytical solutions of the drawdown at early and late times.MATLAB programs were developed to facilitate computation of the semi-analytical solutions.The turbulence factor v which was directly related to the pumping rate appeared to have negligible influence upon the wellbore well function at early times,but imposed significant influence at intermediate and late times.However,the turbulence factor v imposed non-negligible influence upon the aquifer well function during the entire pumping period,provided that the observation point was not suflciently close to the wellbore.Sensitivity analysis indicated that the power index n in the Izbash equation had less influence on the type curves at the face of the pumping wellbore,but had much greater influence upon the well function in the aquifer.As the n values increased,the drawdown in the aquifer decreased at early times and increased at late times.The Boltzmann transformation could only be used in an approximate sense for radial non-Darcian flow problems.This approximation would provide accurate solutions at early times,and introduce small but consistent discrepancies at intermediate and late times for the wellbore well function.

Simulation Experiments in Electromagnetic Tomography Well Logging in Two-phase Flow

Electromagnetic Computer Tomography （ECT） is a method to probe the interior of an inhomogeneous medium via surface measurement in a non-linear way. Due to the great differences in conductivity and permittivity between oil and water in the well, Electromagnetic Tomography Well Logging （ETWL）, a new flow imaging measurement system, is proposed to describe the distribution and movement of oil/water two-phase flow in the well by scanning the detected region and applying a suitable data processing algorithm. The results of the numerical simulation and physical modeling show that the system could provide a clear image of the flow profile.

A model for coupling reservoir inflow and wellbore flow in fishbone wells

A coupling model is proposed in this paper by using the Green Function and Newman＇s product principle, and the solution method is provided here as well. This model can be used to describe the reservoir inflow and wellbore flow for fishbone wells in an unsteady flow or pseudo-steady flow state. A case study indicates that the bottom hole pressure declines quickly in the unsteady flow period which is very short. The pressure drop per unit time remains unchanged under the pseudo-steady flow conditions. The distribution of flow rate along the main wellbore shows a wave shape under the unsteady flow condition, and the flow rate distribution in each branch is similar. The flow rate distribution along the main wellbore is irregular ＂U＂ shaped under the pseudo-steady flow condition, and the space-symmetrical branches have the same flow distribution pattern. In the initial production period, the flow rate increases significantly as the length of branches and the angle between branches and the main wellbore increase. As the production continues, the length and angle of branches have only a slight effect on the flow in fishbone wells.

Numerical Simulation and Experimental Investigation on Performance of the Wells Turbine in Irregular Oscillating Flow

The Wells turbine is an axial-flow air-turbine designed to extract energy from ocean waves. An important consideration is the self-starting capability of the Wells turbine, a phenomenon encountered where the turbine accelerate by itself up to a certain speed for the best turbine performance. In order to clarify the self-starting characteristic and running performance of the Wells turbine in an irregular oscillating flow, a numerical simulation process is established in this paper on the rational assumption of quasi-steady flow conditions, Both self-starting characteristics and running performance are obtained through the numerical simulation and subsequently compared with the experimental data achieved on a computer-controlled oscillating flow test rig which could realize some irregular oscillating flow according to the specified spectrum. Results show that the self-starting time decreases with the increase of the significant wave height and the mean frequency of the irregular oscillating flow, Therefore, it is possible to predict accurately the performance of the Wells turbine by computer simulation.

TWO－PHASE FLOW FOR A HORIZONTAL WELL PENETRATING A NATURALLY FRACTURED RESERVOIR WITH EDGE WATER INJECTION

This paper examines the two-phase flow for a horizontal well penetrating a naturally fractured reservoir with edge water injection by means of a fixed streamlinemodel,The mathematical model of the verical two-dimensional flow or oil-water for a horizontal well in a medium with double-porosity is established ,and whose accuratesolutions are obtained by using the characteristic method .The saturation distributionsin the fractured system and the matrix system as well as the formula of the time of water free production are presented .All these results provide a theoretical basis and a computing method for oil displacement by edge water from naturally fracturedreservirs.

Iterative Method on Well Bore Boundary in Numerical Modeling of Variably Saturated Flow

An iterative method was developed for incorporating the well bore boundary into the finite difference model of water flow in variably saturated porous media. Six cases were presented involving groundwater pumping or injection to demonstrate the advantages of the iterative method over the traditional method. For the iterative method, the total flux gradually approached the well discharge and the flux profile was non-uniform. And the iterative method took into account the variation of well bore water table. Compared to the traditional method, the iterative method can simulate the variably saturated flow caused by pumping or injection more realistically.

Optimization workflow for stimulation-well spacing design in a multiwell pad

A flow mathematical model with multiple horizontal wells considering interference between wells and fractures was established by taking the variable width conductivity fractures as basic flow units.Then a semi-analytical approach was proposed to model the production performance of full-life cycle in well pad and to investigate the effect of fracture length,flow capacity,well spacing and fracture spacing on estimated ultimate recovery(EUR).Finally,an integrated workflow is developed to optimize drilling and completion parameters of the horizontal wells by incorporating the productivity prediction and economic evaluation.It is defined as nested optimization which consists of outer-optimization shell(i.e.,economic profit as outer constraint)and inner-optimization shell(i.e.,fracturing scale as inner constraint).The results show that,when the constraint conditions aren’t considered,the performance of the well pad can be improved by increasing contact area between fracture and formation,reducing interference between fractures/wells,balancing inflow and outflow between fracture and formation,but there is no best compromise between drilling and completion parameters.When only the inner constraint condition is considered,there only exists the optimal fracture conductivity and fracture length.When considering both inner and outer constraints,the optimization decisions including fracture conductivity and fracture length,well spacing,fracture spacing are achieved and correlated.When the fracturing scale is small,small well spacing,wide fracture spacing and short fracture should be adopted.When the fracturing scale is large,big well spacing,small fracture spacing and long fracture should be used.

贵州省地热流体资源可开采资源量研究

综合贵州省地热研究相关成果资料,分析贵州省地热流体资源赋存条件及地热水资源分布特征,以此为基础将贵州省划分为110个地热资源量估算区,参照省内地热流体资源主要集中在断裂带周边的实际特点,采用设计布井法、泉(井)流量统计法和比拟法对贵州地热流体可开采资源量进行估算。结果表明:贵州地热流体资源的形成和分布,受省内地质构造特点及其在全国构造所处部位的控制,地热资源成因类型可划分为沉积盆地传导型地热储和隆起山地断裂对流型地热储,总体热储温度一般小于90℃,为低温地热资源;估算出贵州省地热流体可开采资源总量为23190.37 m^(3)/a,其中设计布井法估算的资源量为15926.22 m^(3)/a,天然温泉可开采资源量1183.34 m^(3)/a,地热井可开采资源量6080.80 m^(3)/a,总热能906933.97 Kw,年开采累计可利用热能量476.68×10^(8)MJ。所估算的地热流体可采资源量可为贵州省地热资源的勘查开发规划提供参考依据。

气井高速非达西效应主控因素分析

气藏开发实践表明,高速非达西效应对气井产能有着重要影响,不同的气藏,高速非达西效应的影响程度是不同的。对于地层压力较低的气藏,当气井产量较高时,高速非达西效应表现比较强;而对于地层压力较高的气藏,相同的气井产量,高速非达西效应可能并不强。其原因在于气体在较高的地层压力下压缩程度很强,密度、黏度更大,天然气的渗流速度更低,高速非达西效应更弱。根据气井产能方程和雷诺数方程,从气井产量、储层物性和气体性质等方面对影响非达西效应的主要因素进行了敏感性研究,基于临界雷诺数得到了达西和非达西渗流界限,建立了天然气达西渗流图版。通过该图版,可以明确非达西效应的强弱,进而为确定气井配产上限提供指导。

井下旋流分离管柱的振动特性研究

为研究旋流分离管柱在注入泵和采出泵两螺杆泵抽吸条件下的振动特性,对其进行模态分析和瞬态动力响应分析。结果表明,不同工况下,旋流分离管柱的固有频率有所不同;固定注入泵一端和固定采出泵一端相比,固定采出泵一端各阶固有频率较小;螺杆泵转动引起的激振力和内部流量变化都会导致管柱变形,其中螺杆泵转动对旋流分离管柱变形影响较大;相对于固定采出泵,固定注入泵条件下旋流分离管柱产生的振动位移更大,是旋流分离管柱自身结构和注入泵转速产生更大激振力综合作用导致的结果;控制两个螺杆泵工作状态的时间差,理想情况下可以控制旋流分离管柱的总变形。

Research on Well Testing Interpretation of Low Permeability Deformed Dual Medium Reservoir

Considering the influence of quadratic gradient term and medium deformation on the seepage equation, a well testing interpretation model for low permeability and deformation dual medium reservoirs was derived and established. The difference method was used to solve the problem, and pressure and pressure derivative double logarithmic curves were drawn to analyze the seepage law. The research results indicate that the influence of starting pressure gradient and medium deformation on the pressure characteristic curve is mainly manifested in the middle and late stages. The larger the value, the more obvious the upward warping of the pressure and pressure derivative curve;the parameter characterizing the dual medium is the crossflow coefficient. The channeling coefficient determines the time and location of the appearance of the “concave”. The smaller the value, the later the appearance of the “concave”, and the more to the right of the “concave”.

火源深度对深井立式空间火灾烟气流动特性及火灾探测方式的影响分析

为掌握深井立式车库、深地矿井等深井立式空间内火灾烟气运动规律,进而对此类火灾进行预警,以某深井地下车库为原型,构建深井立式空间模型,通过数值模拟分析火源深度和热释放速率对深井立式空间火灾烟气流动特性的影响,并掌握温度场和速度场的变化规律。研究结果表明:当火源深度足够大时,由于向上的浮力和速度减小,烟气可能无法到达井口,火源位置越深,其上方热烟气温度越高;并且火源深度对烟气流动的影响存在临界值,即临界深度,当火源高于临界深度时,火源可以从深井出口外卷吸空气,当火源低于临界深度时,火源仅能从深井内部卷吸空气。研究结果可为深井立式空间火灾的预测预警提供科学参考。

利用MODFLOW模拟井流的误差特征

MODFLOW是目前被广泛使用的地下水流数值模型。为分析MODFLOW模拟井流的误差特征,对承压含水层单井抽水问题进行了不同网格尺度下的4组模拟试验。对比模拟水头值与Theis公式解析解,我们将误差分为3类:求解误差、插值误差和模型刻画误差。求解误差是运行MODFLOW核心程序直接产生的,而对格点之间水头分布进行评估时将产生插值误差.最大误差发生在井点位置,这是由数值模型中井周附近水流刻画不合理造成的。

虹吸排水法处理软土地基的水位与沉降计算模型

软土具有渗透性差、承载力低等特性,软土地基的处理一直是岩土工程中的一大难题。利用虹吸免动力排水的特点,可将虹吸排水法应用于软土地基处理中,达到改善土体性质的目的。本文针对虹吸排水法独特的定降深降水模式,先基于离散化的Theis井流模型以及非线性的分层总和法,构建了以孔隙率为核心、渗透系数与压缩模量随固结情况改变的水位与沉降动态计算模型,并与数值模拟结果对比,然后从土体渗透系数、排水板间距以及场地大小3个方面对虹吸排水法处理软土地基的效果进行了分析。结果表明:数值模拟结果验证了计算模型的可靠性,对于浙江沿海不同渗透系数的土体,虹吸排水法均可起到良好的排水固结作用;调整排水板间距可对排水固结时间以及地下水位线起到显著控制作用;排水带来的附加应力随着场地面积的增大向土体深处延伸,对于面积50 m×50 m大小的场地,有效影响深度可达到地表以下27.31 m,远远超出虹吸扬程的极限。在实际的大面积软土地基处理中,虹吸排水法可发挥更好的作用。

高产气井生产管柱非线性流致振动实验研究

三高气井生产管柱在高速流体冲击下容易发生剧烈振动,但目前关于此类流致振动的研究大多集中于理论模型和一些小型室内实验阶段。油气井生产管柱具有其独特性,超大的细长比决定了管柱的整体刚度极低,一般的小型实验系统很难模拟出这样的特点。该研究建立了一个大型生产管柱实验台架,用PE管模拟了一个具有超大细长比特征的油管柱模型,用以模拟生产管柱在高速流体冲击下的振动特性。实验结果表明:三高气井生产管柱在高速流体作用下会以某一固定频率发生振动,振动时管柱中间和底部位置的振幅最大;气体产量越大,管柱振动越剧烈;增加油管壁厚可以有效抑制油管的振动幅度,但不可以改变管柱的振动频率;封隔器安装位置过高或过低都不能起到较好的抑制振动的效果,单个封隔器安装在管柱8/10位置可以起到较好的抑制振动的效果。

煤层气水平井筒倾斜-水平耦合流动规律影响分析

精确掌握煤层气水平井井筒内气液流动规律,对煤层气水平井的合理开发工艺和设备的选择具有重要意义。基于气液两相流理论采用Fluent软件模拟分析的方法,研究了煤层气水平井段倾斜-水平耦合条件下变状态流动规律。分析结果表明:水平段井筒中,上倾斜段井筒内的流动会加剧井筒内气液两相界面的波动。高气、液量下水平段井筒内持液率在流体流动方向上不断增大,低气、液量下水平段井筒内持液率在流体流动方向上不断减小。上倾段倾斜角小于20°时,倾斜角对水平段平均持液率影响较大;下水平段井筒中,倾斜段井筒的长度和倾斜角会影响水平井筒中假想断面的位置,同一流动条件下,出口上倾井筒的倾斜角越大、长度越大,假想断面位置越远离出口端上倾井筒。研究结果可为煤层气水平井下泵深度等排采工艺设计和优选提供理论依据。

Visual-MODFLOW在临汾市土门供水水源地保护区划分中的应用

通过对土门供水水源地的水文地质条件进行分析与概化,建立了研究区的地下水流数学模型。首先应用Visual-MODFLOW软件中的MODFLOW建立了研究区的地下水流场,然后应用MODPATH对水源地开采井进行粒子反向示踪模拟,根据划分地下水源地保护区的时间标准并且结合研究区的水文地质条件,确定了水源地各级保护区的界线。研究成果可为土门水源地地下水的合理开发利用、保护和规划提供科学依据。

高深溜井矿石阶段性流动规律对溜井生产的影响

基于对高深溜井生产实践的长期观察,归纳总结出矿石在高深溜井中的流动规律,提出垂直全断面阶段性流动是高深溜井区别于短溜井特有的工程现象。运用散体材料结构自组织力链和搭拱效应理论,分析了井筒内矿石阶段性流动产生的原因,揭示了高深溜井矿石阶段性流动对溜井生产过程中常见的滞流、堵塞、磨损和片帮现象以及溜井内矿石的混合和分级的影响;分析了溜井内空气气流对散体流动的影响,在正常放矿过程中,流动气体的存在有利于矿石流动和临时平衡拱的破坏;同时,由于受气体的曳力作用,溜井内矿石产生块、粉分级集中现象,助推了井筒内矿石的滞流和堵塞。研究提出矿石的粒级成分、密度、含水量、黏结性及溜井直径、井壁粗糙程度是造成溜井滞流和堵塞的基础因素,垂直全断面阶段性矿石流动特性是造成高深溜井滞流和堵塞的重要原因。

松南气田气井井筒流动规律研究

气井积液已成为松南气田生产中后期面临的一个重要难题,为了明确松南气田气井井筒流动规律及积液程度,本文利用多相管流实验装置开展了70组垂直管气-液两相管流实验,实验条件下共观察到环状流、过渡流、段塞流3种流型,其中过渡流和段塞流表明已经处于积液状态,气井不能正常携带液体,相比环状流,段塞流和过渡流的压力波动幅度较大;利用70组实验模拟结果分别对Hewitt-Roberts流型图版、Duns-Ros流型图版和Gould流型图版进行评价,结果显示Duns-Ros流型图版准确率最高,但依然无法满足精度需求,利用实验数据分别对Duns-Ros流型图版中的过渡流-环状流转换边界、段塞流-过渡流转换边界进行修正,建立了新的流型图版,并对A1井进行了分析,结果显示修正后的流型图版能够准确反映A1气井的生产状态,为气井积液的预测及排水采气工艺技术的介入时机提供了理论指导。

渗流运动虚拟仿真实验平台设计与实现

下渗实验与井流实验是水文地质学科专业基础教学的重要实践内容,灵活开展定水头、变水头下渗及潜水、承压水井流实验是对本科生专业技能训练的基本要求。由于实验设备与空间不足,在有限学时内,无法为学生呈现完整的实验过程,且渗流运动发生于看不见摸不到的地面以下,对其理解具有一定难度,制约实验教学效果。为此,设计包气带—饱和带渗流运动模拟虚拟仿真实验平台,涵盖实验导学、下渗实验与井流实验等主要环节,重点模拟包括野外样品采集与理化性质测试、装填土柱等基本实验操作环节,同时拓展降水条件下,野外变水头下渗及井流过程的交互式虚拟仿真实验。通过可视化的仿真结果,帮助学生理解下渗及井流过程,为提升水文地质专业实践教学效果提供了一种有效途径。