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Production rate and cumulative production models for advanced decline curve analysis of gas reservoirs.

机译：气藏先进的下降曲线分析的生产率和累计产量模型。

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摘要

Production rate and cumulative production data from gas reservoirs are routinely analyzed using dimensionless "type curves", which are plots of numerical, analytical, or sometimes empirical solutions to the gas diffusivity equation. These solutions are theoretically developed by coupling the boundary-dominated flow equation with the gas material balance equation. Due to the mathematical difficulty of this process, past efforts have focused on approximate models based on simplifying assumptions. Two basic limitations of these models are: (1) The use of approximate linearization schemes (i.e., the zero-order and first-order polynomial models) for correlating the non-linear viscosity-compressibility term, and (2) Assumption of zero or constant bottomhole pressure production.;This work aims to eliminate these restrictive assumptions by proposing semi-analytical solutions developed from the rigorous equations underlying production rate-time analysis models. Pseudopressure and pseudotime functions are also avoided in this work because knowledge of average reservoir pressure is required for computing pseudotime which makes the procedure iterative.;We examine several linearization schemes (zero-order, first-order and general polynomial functions, as well as exponential function) for modeling the non-linear terms. Simulation studies conducted using different gas systems show that the general polynomial function is applicable to all gas reservoirs.;More importantly, this work demonstrates that a third-order polynomial function is adequate for linearizing the gas flow equation during reservoir depletion. Simultaneous solution of the linearized flow and gas material balance equations yields a first-order ordinary differential equation in terms of cumulative production and time. This formulation can be used for variable bottomhole pressure data analysis since bottomhole pressure is isolated explicitly.;The rate and cumulative production models are derived in terms of dimensionless variables to facilitate development of both analytical and graphical solutions (type curves). Closed form predictive equations for cases of constant bottomhole pressure production using the approximate exponential function are presented--these expressions are accurate only for high pressure gas reservoirs. Numerical solutions are also presented for the general polynomial model.;Comparison of the new solutions with Carter type curves shows excellent agreement between the rate responses. Finally, we can estimate reservoir parameters (original-gas-in-place and permeability) by applying these new solutions to field data.
机译：通常使用无量纲“类型曲线”来分析气藏的生产率和累积产量数据，这些曲线是气体扩散率方程的数值，分析或有时为经验解的图。这些解决方案是通过将边界支配的流动方程式与气体材料平衡方程式耦合而在理论上开发的。由于此过程的数学难度，过去的工作集中在基于简化假设的近似模型上。这些模型的两个基本局限性是：（1）使用近似线性化方案（即零阶和一阶多项式模型）来关联非线性粘度-压缩率项，以及（2）假设零或零恒定井底压力生产。这项工作旨在通过提出由生产率速率-时间分析模型背后的严格方程式开发的半解析解来消除这些限制性假设。在这项工作中还避免了伪压力和伪时间函数，因为计算伪时间需要了解平均油藏压力，这使得该过程可以迭代。我们研究了几种线性化方案（零阶，一阶和一般多项式函数以及指数函数）函数）以对非线性项进行建模。使用不同气体系统进行的模拟研究表明，通用多项式函数适用于所有储气库。更重要的是，这项工作表明，三阶多项式函数足以线性化储气层枯竭期间的气体流动方程。线性化的流量和气体物料平衡方程的同时求解产生了一个基于累积产量和时间的一阶常微分方程。由于明确隔离了井底压力，因此该公式可用于可变井底压力数据分析。速率和累积生产模型是根据无量纲变量导出的，从而有助于开发解析和图形解决方案（类型曲线）。提出了使用近似指数函数的恒定井底压力产生情况的闭合形式预测方程式-这些表达式仅对于高压气藏是准确的。还给出了针对一般多项式模型的数值解。;与Carter型曲线的新解的比较表明，速率响应之间具有极好的一致性。最后，我们可以通过将这些新的解决方案应用于油田数据来估算储层参数（原始天然气和渗透率）。

著录项

  • 作者

    Ansah, Joseph.;

  • 作者单位

    Texas A&M University.;

  • 授予单位 Texas A&M University.;
  • 学科 Engineering Petroleum.
  • 学位 Ph.D.
  • 年度 1996
  • 页码 168 p.
  • 总页数 168
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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