Abstract The results of modeling nonlinear transport properties on a plug scale for steady state, unsteady state, pulse decay and sinusoidal pressure measurements are presented. We include the gas slippage (Klinkenberg corrections) and pressure dependent density effects. To validate the modeling, we compare it to analytical calculations based on an assumption of constant mass flow once the transients have dissipated for steady state models. Validation of the other measurement protocols is performed by comparison to finite difference calculations. For low permeability samples, significant pressure drops must be modeled to obtain large enough flow rates to allow accurate measurement in the laboratory. We limited ourselves to 100 psi pressure differences because of the large influence of effective stress on gas density that would be present for larger pressure differences. Flowing pressures of this magnitude imply significant pressure dependent density effects, which reduce the flow rates. In contrast, gas slippage increases the transport of gas. The result is that nearly identical fits are obtained for widely varying magnitudes of permeability and gas slippage. This result is obtained for all of the modeled measurement protocols. We introduce a new technique to interpret the modeled data, the ”k0-b plot”. The method allows the values of k0 and b to be extracted if multiple measurements are performed at different mean pressures. The technique is also compared to laboratory data to demonstrate that the effects occur in the measurements. The influence of the non-linearities predicted on the measured chamber pressures are presented for each of the measurement protocols (other than steady state in which there are no chambers). In particular, sinusoidal pressure variation of the upstream chamber results in an increased average downstream chamber pressure and the introduction of harmonic distortion. These effects have not been discussed in the literature and give a motivation for development of this measurement for low permeability samples. The modeling indicates that plug scale measurements are practical, but multiple mean pressures must be used to separate the competing effects of permeability and gas slippage. We recommend performing unsteady state measurements at reservoir stress at multiple mean pressures, supplemented with sinusoidal pressure and pulse decay to calibrate the nonlinear and adsorption effects.

中文翻译：

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非线性传输特性对低渗透率测量的影响

摘要 介绍了在塞尺度上对稳态、非稳态、脉冲衰减和正弦压力测量的非线性输运特性进行建模的结果。我们包括气体滑移（Klinkenberg 修正）和压力相关的密度效应。为了验证建模，我们将其与基于恒定质量流量假设的分析计算进行比较，一旦稳态模型的瞬态消散。其他测量协议的验证是通过与有限差分计算进行比较来执行的。对于低渗透率样品，必须对显着的压降进行建模，以获得足够大的流速，以便在实验室进行准确测量。我们将自己的压力差限制在 100 psi，因为有效应力对气体密度的影响很大，而气体密度会在较大的压力差下出现。这种量级的流动压力意味着显着的压力相关密度效应，这会降低流速。相反，气体滑移增加了气体的输送。结果是对于渗透率和气体滑移的广泛变化量级获得几乎相同的拟合。该结果是针对所有建模的测量协议获得的。我们引入了一种新技术来解释建模数据，即“k0-b 图”。如果在不同的平均压力下进行多次测量，则该方法允许提取 k0 和 b 的值。该技术还与实验室数据进行了比较，以证明测量中发生了影响。对于每个测量协议（除了没有腔室的稳态），预测的非线性对测量的腔室压力的影响。特别是，上游室的正弦压力变化导致平均下游室压力增加和谐波失真的引入。这些影响在文献中没有讨论过，这为开发低渗透率样品的这种测量提供了动力。建模表明，塞尺度测量是实用的，但必须使用多个平均压力来分离渗透率和气体滑脱的竞争效应。我们建议在多个平均压力下在储层应力下进行非稳态测量，