Current gas rate decline analysis methods in boundary-dominated flow (BDF) are mainly based on Arps' empirical decline models, or the liquid-based analytical models associating with pseudo-variables. Recently, Stumpf and Ayala (2016), and Wang and Ayala (2020) demonstrated that the decline exponents (b) used in Arps’ hyperbolic model can be rigorously estimated in advance for both constant and variable conditions regardless of reservoir properties and before collecting any production data. In this paper, we further investigate the gas rate flow behavior for heterogeneous reservoir, which is characterized by fractal properties. The decline exponents (b) are thus re-derived based on the gas flow rate equation in BDF, and it is shown that the expression of decline exponents can be written in the same format with homogeneous reservoir by defining new productivity indexes. This allows for the application of the step-by-step explicit original-gas-in-place (OGIP) determination methods proposed by Stumpf and Ayala (2016), and Wang and Ayala (2020) in fractal radial flow. However, due to the heavily pressure depletion before BDF for linear flow, the average value of decline exponent (donated as b_i) is not available any more. Therefore, our explicit OGIP determination method CANNOT be directly applied, which would lead to the underestimation of the true value if it is blindly used. Finally, several simulated cases are discussed to validate the capabilities of the methodology. The finding of this study can help for better understanding of the gas rate decline behavior in heterogeneous reservoirs.

当前边界控制流（BDF）中的气体速率下降分析方法主要基于Arps的经验下降模型或与伪变量关联的基于液体的分析模型。最近，Stumpf和Ayala（2016）以及Wang和Ayala（2020）证明，无论储层性质如何，在恒定和可变条件下，Arps双曲模型中使用的下降指数（b）都可以预先精确估计，然后再收集生产数据。在本文中，我们进一步研究了以分形特征为特征的非均质油藏的瓦斯流量行为。下降指数（b因此，根据BDF中的气体流速方程重新推导），并表明可以通过定义新的生产率指标，用均质储层以相同格式写出下降指数的表达式。这允许将Stumpf和Ayala（2016）以及Wang和Ayala（2020）提出的分步径向显式原位气体（OGIP）确定方法应用在分形径向流中。但是，由于线性流动在BDF之前压力很大，所以下降指数的平均值（表示为b _i）不再可用。因此，不能直接应用我们的显式OGIP确定方法，如果盲目使用它会导致对真实值的低估。最后，讨论了几个模拟案例以验证该方法的功能。这项研究的发现可以帮助更好地了解非均质油藏中的气速下降行为。