Abstract In gas condensate reservoirs (GCR) operating below dewpoint pressure, two-phase conditions introduce non-linearities into the diffusivity equation, rendering conventional single-phase production data analysis unreliable. Recent studies, presented in a companion paper published in 2018, demonstrated the application of an equivalent single phase approach to improve the quality of GCR production data analysis using “Blasingame” type curves. That study analysed production data from radial GCR simulation models with fluid maximum liquid dropout ranging from 1% to 42%. The pressure-saturation/kr data for the computation of equivalent-phase pseudovariables was determined using an approach based on two-phase steady-state (SS) theory. For saturated reservoirs, less consistent improvements in permeability, skin and drainage area estimates were obtained – an observation attributed to unrepresentative pressure-saturation/kr data. This current study builds on the earlier work, by examining alternative sources of pressure-saturation data for use in the analysis of saturated GCR cases. PVT liquid-saturation curves and sufficiently representative pressure-saturation responses from the near-wellbore region of numerical simulations are considered. The results suggest that pressure-saturation data representative of the response in the near-wellbore region during transient flow is adequate for the two-phase analysis of long term production data using type curves. The results further highlight reservoir and well operating conditions under which each source of pressure-saturation data is most suitable for use with the equivalent-phase approach. A new time-based adjustment is also introduced to improve the quality of the equivalent-phase type curve analysis for cases in which the entire reservoir becomes saturated prior to stable boundary dominated flow (BDF) conditions. Finally, results are presented which show that our equivalent-phase approach can be successfully combined with other conventional production data analysis tools, e.g. type curves for hydraulically fractured wells, and straight-line techniques used in the analysis of BDF data, all of which were originally developed for analysing single phase systems.

中文翻译：

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凝析气藏生产数据分析的等效单相方法

摘要 在低于露点压力的凝析气藏 (GCR) 中，两相条件将非线性引入到扩散方程中，使传统的单相生产数据分析变得不可靠。最近在 2018 年发表的一篇配套论文中提出的研究表明，应用等效的单相方法来提高使用“Blasingame”类型曲线的 GCR 生产数据分析的质量。该研究分析了径向 GCR 模拟模型的生产数据，其中流体最大液体下降范围为 1% 至 42%。用于计算等效相位伪变量的压力饱和度/kr 数据是使用基于两相稳态 (SS) 理论的方法确定的。对于饱和储层，渗透率的改善不太一致，获得了皮肤和引流面积估计值 - 归因于不具代表性的压力饱和度/kr 数据的观察结果。目前的研究建立在早期工作的基础上，通过检查用于分析饱和 GCR 案例的压力饱和数据的替代来源。考虑了数值模拟的近井筒区域的 PVT 液体饱和度曲线和充分代表性的压力饱和度响应。结果表明，在瞬态流动期间代表近井筒区域响应的压力-饱和数据足以使用类型曲线对长期生产数据进行两相分析。结果进一步突出了油藏和井的操作条件，在这些条件下，压力饱和度数据的每个来源最适合与等效相方法一起使用。对于整个储层在稳定边界主导流 (BDF) 条件之前变得饱和的情况，还引入了一种新的基于时间的调整，以提高等效相类型曲线分析的质量。最后，给出的结果表明，我们的等效相方法可以成功地与其他传统的生产数据分析工具相结合，例如水力压裂井的类型曲线，以及用于 BDF 数据分析的直线技术，所有这些都是最初开发用于分析单相系统。