低渗气藏产水水平井井筒压降规律研究

利用水平井开发低渗透气藏过程中,产水使得水平井筒压降规律异于井筒单相压降,因此分析产水水平井井筒压降规律至关重要。该文基于气水两相渗流原理以及水平井周围椭圆形渗流场,考虑启动压力梯度、应力敏感性、滑脱效应以及高速非达西流动等因素的影响,定义气水两相广义拟压力,得到了低渗气藏中气水同产水平井地层渗流模型,并考虑水平井筒变质量流动,建立了地层两相渗流与井筒两相管流的耦合模型。实例分析发现:低渗气藏水平井井筒压降约为0.01 MPa,远远大于气藏单相井筒压降。由敏感性分析可知,随着水气体积比和滑脱因子的逐渐增大,井筒压降不断增大,而随着启动压力梯度和应力敏感指数的增大,井筒压降则不断减小。该文为低渗气藏气水同产水平井井筒压降规律的研究提供了新的思路。     

水平井井筒内压力产量变化规律研究

对水平井生产系统进行分析,必然涉及到井筒中的流动问题,过去人们不考虑水平井井筒中的压降,这给水平井的生产系统分析带来较大的误差。本文考虑井筒摩擦和加速度对井筒压降的影响,同时考虑地层渗流和水平井筒流动,建立了水平井井筒流动与地层流动耦合的数学模型,以此获得了计算水平井井筒压降和产量分布的表达式,实例计算和分析了海上油藏一口水平井井筒的压力和产量变化规律。本文的研究为水平井的生产系统分析提供了理论基础。     

压裂水平井裂缝变质量入流与油藏渗流耦合模型研究

综合考虑了水平井筒完井段生产、各条裂缝长度不等、导流能力不同、间距不等、与水平井筒夹角不等以及关于井筒非对称等因素对产量的影响,建立了压裂水平井裂缝分段入流、水平井筒分段入流与油藏渗流的耦合模型.通过实例计算,揭示了水平井筒完井段及裂缝段的入流和压力分布规律,并对各裂缝的产量进行了敏感性分析.结果表明,在裂缝与井筒交点附近,裂缝入流存在局部极大值,且生产压差最大;裂缝之间的水平井筒完井段入流速度存在极大值,在裂缝与井筒交点处压力变化幅度剧增;裂缝半长对外裂缝产量影响程度深,对內裂缝的影响相反.     

裂缝参数对压裂水平井产能影响规律分析及重要性排序

基于等效井径模型、裂缝内线性流动模型、井筒变质量流动模型,运用势叠加原理,建立了压裂水平井油藏渗流与井筒管流耦合模型.研究分析了裂缝参数对其压裂水平井产能影响规律,并运用灰色关联因素分析方法,给出了裂缝参数对其产能影响的重要性排序方法,解决了压裂水平井裂缝参数重要性排序问题.同时该耦合方法可以推广应用到多分支复杂结构井的油藏渗流与井筒管流的耦合.     

水平井筒变质量分散泡状流压降的理论与实验研究

由于水平井筒和常规水平管道中气液两相流动的相似和差别，可以预知常规水平管流的压降计算方法对于井筒流动来说就需要进行修正或扩展。本文对气、液两相分别应用质量守恒方程和动量守恒方程，考虑管壁存在人流或出流对于分层流流型压降的影响，得到水平井筒气液两相变质量流动分散泡状流流型的压降计算方法。同时，设计并建立了水平井筒流体流动模拟实验装置，在轴向为气液两相流动的前提下分别进行了上管壁单孔眼注入和下管壁单孔眼注入的压降实验研究，获得了大量的实验数据。实验数据和理论计算结果吻合很好，这表明该计算方法具有实际应用价值。     

高温热采井水泥环缺陷对套管安全性的影响分析

针对水泥环缺陷导致套管承受非均匀载荷并引起套管失效的问题,建立了套管、含缺陷水泥环和地层耦合系统有限元计算模型。将温度场与应力场耦合,考虑套管强度降低,计算了水泥环缺陷形状、缺陷环向开度、缺陷深度及缺陷数量对套管安全的影响。应用塑性变形、剩余强度和安全系数来评价水泥环含缺陷井筒中套管的安全性,并分析了套管的失效模式。计算结果表明:完整井筒和水泥环含缺陷井筒中套管的屈服温度相差较大,水泥环缺陷环向开度和深度对套管安全的影响比较大。此研究为揭示套管失效机理提供了依据,对预防套损具有指导意义。     

井间干扰对油水两相流数值试井曲线的影响

井间干扰会对试井曲线的影响非常大。本文用数值试井方法研究了井间干扰对试井曲线的影响，采用PEBI网格技术，给出了在PEBI网格下油水两相流动控制方程的离散形式，并耦合了井筒存储和表皮系数公式，得到了压力降落数值试井问题的产量模型。对三种井部署情况经数值试井模型计算并对比发现，双对数曲线的早期段保持一致，由于干扰井的影响，中后期段变化非常明显，干扰井越多，测试井压降越快，试井曲线上抬幅度越大。     

蒸汽沿井筒流动过程数值模拟

蒸汽沿井筒流动过程中,蒸汽参数(压力、温度及干度等)、径向散热损失和垂向压力能损失,均沿流动过程变化。本文运用传热学、热力学及流体力学等学科知识,建立了井筒数值模拟综合计算模型,给出了求解方法,并进行了模拟计算。本文所建模型,综合考虑了蒸汽流动过程中压力、温度、干度和热损与压降的相互影响,给出了更为精确的无因次时间函数的表达式,通过试验确定了接箍对总传热系数的影响,同时也通过试验修正了隔热管性能变化对隔热性能的影响。     

气井瞬变流动压力、温度耦合模型半解析解

根据异常高压气井测试特点,建立了一套预测气井井筒压力、温度耦合模型,利用LapLace变换详细推导获得了瞬变流动井筒压力、温度耦合模型在各种情况下的拉氏空间通解,运用Stehfest数值反演技术得到井底压力及温度实空间解。并运用VC++6.0语言,研制了异常高压气井井口压力资料处理软件。该软件已经在新疆、四川等油气田投入使用。矿场使用情况表明:文中提出的理论和方法切实可行,解决了由于温度引起的异常高压特高产气井井口压力动态异常问题,因而,具有重要的理论研究和实际应用价值。     

分段变密度射孔水平井底水入流规律研究

分段变密度射孔是目前水平井开发底水油藏非常重要的一类完井方式,而底水脊进模型的分析计算是进行完井优化的理论基础。该文以分段和变密度两类射孔方式下的水平井为研究对象,在稳态产能模型的基础上,结合活塞式驱油原理,建立了精细考虑每个孔眼中的流体流动、井筒压降及避射段影响的底水脊进模型,刻画水脊形态,研究底水突破模式。研究结果表明改变沿井筒方向上射孔密度的分布,可以调节入流剖面形状,跟段密的射孔类型能使入流剖面较均匀,可以用来延长底水突破时间;而水平井筒上布置避射段,单个生产段的底水突破模式与单个水平井类似,并可以进行出水层段的封堵。     

阶梯水平井生产段油藏渗流与井筒变质量管流的耦合模型

随着油气勘探和开发技术的迅猛发展，阶梯水平井作为水平井的一种特殊井型，日益在国内外油田得到广泛应用。基于势叠加原理和镜像反映原理，推导出了薄互层油藏中阶梯式水平井生产段的空间势分布；采用微元线汇理论和动量守恒定律建立了薄互层油藏阶梯水平井生产段沿程压降计算模型。推导出了裸眼完井方式下阶梯水平井生产段油藏渗流与井简变质量管流耦合的数学流动模型，并提出了相应的数学解法。     

A NEW METHOD FOR PREDICTION OF PRODUCTIVITY OF FRACTURED HORIZONTAL WELLS BASED ON NON-STEADY FLOW

Hydraulic fracturing technologies of horizontal well are important ways to develop oil-gas field with low permeability. Productivity forecast of fractured horizontal wells is a difficult problem of hydraulic fracturing technologies. Basing on non-steady flow of fractures fluid during production, applying potential function principles, superposition principle and mathematical method for solving, coupling of seepage flow in the formation and pipe flow in the well bore, a new model on multi-fracture interference productivity forecast of fractured horizontal well is established in this article. The results indicate the coincidence rate between this model and practice is high. The pressure loss in the horizontal well bore has definite influence on the production status of fractured horizontal wells. The productions of different fractures in horizontal well bore are unequal, the productions of outer fractures are higher than middle fractures; the pressure in the well bore shows an uneven distribution, the pressure declines gradually from finger tip to heel end. Asymmetry of fractures may make productivity of fractured horizontal wells decline. The conclusions are instructive in designing fractured horizontal well for low permeability reservoir.     

水平井油藏数值模拟的有限元方法

本文对底水油藏水平井三维两相渗流的数学模型给出了一种有限单元解法。在求解过程中，对压力场采用基于Ｇａｌｅｒｋｉｎ方法的经典有限元技术，对饱和度场，引入了非标准的不连续有限元方法，以反映实际油藏中水驱前缘的含水饱和度不连续跃度的性质。整个过程采用计算功能极强的ＮＤＰ－ＦＯＲＴＲＡＮ语言编程实现，对有限元整体刚度矩阵采用变带宽一维压缩存储，以节省数组存储空间，进一步提高程序的运算能力和运行速度。     

A NOVEL 3-D MODEL FOR THE WATER CRESTING IN HORIZONTAL WELLS

In the presence of bottom water, a drop in the reservoir pressure due to fluid production causes the aquifer water to expand and to flow into the reservoir. Therefore, hydrocarbon production from a well is limited by the critical flow rate. The main purpose of this study is to investigate the breakthrough time and the critical rate by using a novel 3-D horizontal well model. Based on the hypothesis that the horizontal well is located in any position of a circular reservoir with no-flow boundary on the top of the reservoir and constant pressure boundary at the bottom, the horizontal well has been regarded as an infinite conductivity line sink and then a 3-D steady-state flow model of the horizontal well is set up. A point sink pressure solution can be obtained with the Fourier transform. The result of the pressure distribution of the uniform flux horizontal well can be presented by means of the principle of superposition. According to the stable water cresting theory, this study confirms the stable height of water cresting and the critical rate. Meanwhile, it can re-confirm the breakthrough time at a specific rate. The output of a comparison between this 3-D model and the reservoir numerical simulator （Eclipse） shows the method presented here can be applied to investigate the behavior of a water cresting and to predict the breakthrough time at the bottom water driver reservoir.     

WELL TESTING ANALYSIS FOR HORIZONTAL WELL WITH CONSIDERATION OF THRESHOLD PRESSURE GRADIENT IN TIGHT GAS RESERVOIRS

A fundamental solution for homogeneous reservoir in infinite space is derived by using the point source function with the consideration of the threshold pressure gradient. The fundamental solution of the continuous point source function is then derived based on the Green function. Various boundary conditions of the reservoirs are considered for this case and the corresponding solutions are obtained through the mirror image reflection and the principle of superimposition. The line source solution is obtained by integration. Subsequently, the horizontal-well bottom hole pressure response function for a non-linear gas flow in the homogeneous gas reservoir is obtained, and the response curve of the dimensionless bottom hole pressure and the derivative for a horizontal well in the homogeneous gas reservoir are obtained. In the end, the sensitivities of the relevant parameters are analyzed. The well test model presented in this paper can be used as the basis of the horizontal well test analysis for tight gas reservoirs.     

ANALYSIS OF TWO-PHASE FLOW PRESSURE BUILDUP DATA FROM A WELL IN AN INFINITE MULTIWELL RESERVOIR

NOMENCLATURE A1———drainage area of the tested well ( Well 1) At———total reservoir drainage area B———two-phase formation volume factor C———wellbore storage coefficient Cf———rock compressibility fator Co———oil compressibility fator Cw———water compressibility fator Ct———compressibility fator K———reservoir permeability m———slope of a semilog straight line m1———slope defined by Eq.(12) p-———average reservoir pressure-pD———di mensionless average drainag…