双层气藏非线性渗流模型试井分析

发布时间：2019-07-03 19:50

【摘要】：由于沉积的原因,天然气藏通常由多个储层组成,并且各储层的性质不尽相同。在进行天然气开采时,从经济的角度往往会考虑同时射开多个地层进行开采,这样一来,各地层的气体将同时流向井筒,各地层间会相互影响。因此,对于双层气藏不能用均质单一地层的气藏模型进行求解分析。本文通过对双层气藏渗流机理的研究,建立了三种不同外边界条件下考虑表皮效应以及井筒储集效应的定产量生产的圆形双层气藏不稳态渗流数学模型。对于气藏来说,由于天然气性质比如粘度、压缩系数、偏差因子等都与压力有关,因此控制方程具有很强的非线性,但通过引入拟压力函数可以将控制方程线性化。在将控制方程线性化过程中,本文分别讨论了将扩散系数强行近似后的双层气藏线性渗流模型的求解和考虑扩散系数随压力的变化后的双层气藏非线性渗流模型的求解。通过定义拟时间因子,可以将考虑扩散系数时的双层气藏的控制方程线性化,从而利用拉普拉斯变换以及贝塞尔函数对考虑扩散系数时的三种不同外边界条件下考虑表皮效应以及井筒储集效应的双层气藏不稳态渗流数学模型进行求解。本文通过求解三种不同外边界条件下考虑表皮效应以及井筒储集效应的定产量生产的圆形双层气藏非线性渗流模型的井底拟压力解和各地层产量解,分别绘制出双层气藏无量纲井底拟压力、无量纲井底拟压力导数以及各地层无量纲产量和时间的关系图版。进一步讨论了井筒储集系数、表皮因子、层间流动系数比、层间储容比、初始地层压力、泄流半径等多种影响因素分别对三种不同外边界条件下考虑表皮效应以及井筒储集效应的定产量生产的圆形双层气藏的井底压力以及各地层产量的影响及其敏感性,并进行了相应的实例分析。本文绘制的试井分析图版,可以用来分析和推算地层和井筒的各项参数,并为准确描述双层气藏的动态特征和预测生产趋势提供了依据。
[Abstract]:Due to sedimentary reasons, natural gas reservoirs are usually composed of multiple reservoirs, and the properties of each reservoir are not the same. In the process of natural gas exploitation, from the economic point of view, multiple strata will be fired at the same time, so that the gas of each formation will flow to the wellbore at the same time, and each formation will affect each other. Therefore, the gas reservoir model of homogeneous single formation can not be used to solve the double layer gas reservoir. Based on the study of seepage mechanism of double-layer gas reservoir, three mathematical models of unstable seepage of circular double-layer gas reservoir with fixed production considering skin effect and wellbore reservoir effect under three different external boundary conditions are established in this paper. For gas reservoirs, because the properties of natural gas, such as viscosity, compression coefficient and deviation factor, are related to pressure, the governing equation is strongly nonlinear, but the governing equation can be linearized by introducing quasi-pressure function. In the process of linearizing the governing equation, the solution of the linear seepage model of the double-layer gas reservoir and the solution of the nonlinear seepage model of the double-layer gas reservoir considering the variation of the diffusion coefficient with the pressure are discussed respectively in this paper. By defining the quasi-time factor, the governing equation of the double-layer gas reservoir considering the diffusion coefficient can be linearized, and the mathematical model of unstable seepage of the double-layer gas reservoir considering the skin effect and wellbore reservoir effect under three different external boundary conditions considering the diffusion coefficient can be solved by using Laplace transform and Bessel function. In this paper, by solving the bottom hole quasi-pressure solution and each formation production solution of nonlinear seepage model of circular double-layer gas reservoir considering skin effect and wellbore reservoir effect under three different external boundary conditions, the dimensionless bottom hole quasi-pressure derivative and dimensionless bottom hole quasi-pressure derivative of double-layer gas reservoir and the relationship between dimensionless production and time of local strata are drawn respectively. Furthermore, the influence and sensitivity of wellbore reservoir coefficient, skin factor, interlayer flow coefficient ratio, interlayer storage capacity ratio, initial formation pressure and discharge radius on the bottom hole pressure and local production of circular double layer gas reservoir with fixed production considering skin effect and wellbore storage effect under three different external boundary conditions are discussed, and the corresponding examples are given to analyze the influence and sensitivity of wellbore storage coefficient, skin factor, interlayer flow coefficient ratio, interlayer storage ratio, initial formation pressure and discharge radius on the bottom hole pressure and local production of circular double layer gas reservoir with fixed production under three different external boundary conditions. The well test analysis chart drawn in this paper can be used to analyze and calculate the parameters of formation and wellbore, and provides a basis for accurately describing the dynamic characteristics of double-layer gas reservoirs and predicting the production trend.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE353;TE312

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