基于一维时间扩散飞行方法的非均质裂缝性砂岩气藏试井模型

Well test model for heterogeneous fractured tight sandstone gas reservoirs based on the one-dimensional diffusive time of flight method

摘要

非均质裂缝性砂岩储层经酸化压裂后，井周可能形成条状裂缝带。为准确刻画非均质裂缝性砂岩气藏的生产动态，采用一维时间扩散飞行（1D-DTOF）方法，建立非均质裂缝性砂岩气藏数学模型，应用 Laplace 变换、杜哈美原理和 Stehfest 数值反演对模型进行求解，获得井底流压响应的解析解，绘制不稳定的井底压力响应曲线。根据压力响应曲线特征划分流动阶段，分析敏感性因素。结果表明：非均质裂缝性砂岩气藏压裂井的渗流过程可划分为 5 个典型流动阶段；裂缝网络密度越大，窜流现象发生时间越早，窜流阶段压力导数曲线的凹陷深度越大；近井地带的渗透率越大，线性流阶段的持续时间越长；远井地带的孔隙度越大，储层进入边界流阶段的时间越晚；近井区域孔隙度极差越大，对窜流阶段的影响越显著；远井区域孔隙度极差越大，对边界流阶段的影响越显著。现场应用验证非均质裂缝性砂岩气藏试井模型在实际应用中的有效性和可靠性，为解决酸化压裂非均质裂缝性砂岩气藏中条状裂缝带问题提供支持。

Abstract

After acid fracturing in heterogeneous fractured sandstone reservoirs, strip-shaped fracture zones may form around the wellbore. To accurately characterize the production dynamics of heterogeneous fractured sandstone gas reservoirs, a mathematical model based on the one-dimensional diffusive time of flight(1D-DTOF) method was established. The model was solved using Laplace transform, Duhamel's principle, and Stehfest numerical inversion techniques to derive an analytical solution for bottomhole flowing pressure responses, generating transient pressure response curves. The flow stages were classified based on curve characteristics, and sensitivity analyses of influencing factors were conducted. The results indicate that the seepage process in heterogeneous fractured wells can be divided into five typical flow stages. A higher fracture network density leads to earlier occurrence of fluid channeling and deeper depressions in the pressure derivative curves during the channeling stage. Increased permeability in the near-well zone prolongs the duration of the linear flow stage. Higher porosity in the far-well zone delays the onset of boundary-dominated flow. Greater porosity contrast in the near-well region significantly impacts the channeling stage, while higher porosity contrast in the far-well region notably affects the boundary-dominated flow stage. Field applications validated the effectiveness and reliability of this well testing model, providing technical support for addressing strip-shaped fracture zone challenges in acid-fractured heterogeneous sandstone gas reservoirs.

关键词

酸化压裂 / 裂缝性气藏 / 非均质性 / 一维时间扩散飞行 / 试井模型 / 裂缝网络

Key words

acid fracturing / fractured gas reservoirs / heterogeneity / one-dimensional diffusive time of flight(1D-DTOF) / well testing model / fracture network

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基金资助

国家自然科学基金项目(52104043)