Core-scale measurements are considered the ground truth that oil and gas or electric utility companies use to predict the migration of fluids such as oil, natural gas, carbon dioxide, or brine deep underground during their extraction or injection operations. To provide a greater understanding of petrophysical properties of low-permeability geologic formations such as shales and tight gas sandstones, this study introduces a novel core-analysis procedure. The technique follows conventional pressure-pulse-decay permeametry, where the pressure in an inlet chamber adjacent to a cylindrical core plug undergoes a rapid pressurization, the system is shut in, and the pressure reaches a new equilibrium. However, unlike a standard unidirectional pressure-pulse decay, the full-immersion pressure-pulse decay (Hannon 2019) applies a pressure disturbance to the entire outer surface area of the sample. This article covers the numerical simulator designed to model flow through an anisotropic porous sample in this scenario. The model assumes distinct but uniform permeabilities along the radial and axial directions of the cylindrical plug sample. When extracting a plug vertically (or perpendicular to bedding), the permeability along the radial direction associates with the horizontal permeability (i.e., parallel to bedding), whereas in the axial direction, flow occurs perpendicular to bedding (a vertical permeability). Investigations of these model outputs demonstrate an approximately 20-fold decrease in time to complete a full-immersion experiment compared with conventional pressure-pulse decay. Furthermore, the pressure-decay curves resulting from the full-immersion method have slightly different shapes than those resulting from other unidimensional transient methods. These differences begin to demonstrate that, under achievable experimental conditions, the analysis of pressure data from one full-immersion test could enable the simultaneous estimation of the apparent permeabilities parallel and perpendicular to bedding of a cylindrical sample in addition to its porosity. A follow-up article finalizes the proof of this capability with a parameter-estimation procedure and presents experimental verification through a proof-of-concept study. Described in greater detail in that article, the parameter estimator requires multiple forward simulations to analyze the data, which behooves minimizing the compute time for each simulation. By using an alternating direction implicit time-marching scheme and a structured but variably spaced grid, the numerical simulator built for this purpose provides a forward model output with suitable accuracy in approximately 0.5 seconds.

岩心规模的测量被认为是石油和天然气或电力公司在提取或注入作业期间用来预测地下深处的流体（例如石油，天然气，二氧化碳或盐水）迁移的基本事实。为了更好地了解低渗透性地质构造（如页岩和致密气砂岩）的岩石物理特性，本研究引入了一种新颖的岩心分析程序。该技术遵循常规的压力-脉冲-衰减渗透率法，在该方法中，邻近圆柱形芯塞的进气腔中的压力经历了快速加压，系统被关闭，压力达到了新的平衡。但是，与标准的单向压力脉冲衰减不同，全浸没压力脉冲衰减（Hannon 2019）对样品的整个外表面施加压力扰动。本文介绍了用于在这种情况下对各向异性多孔样品的流动进行建模的数值模拟器。该模型假定沿圆柱状塞子样品的径向和轴向具有不同但均匀的渗透率。当垂直（或垂直于层理）抽出塞子时，沿径向的渗透率与水平渗透率（即，平行于层理）相关联，而在轴向方向上，垂直于层理（垂直渗透率）发生流动。对这些模型输出的研究表明，与传统的压力脉冲衰减相比，完成全浸没实验所需的时间减少了约20倍。此外，全浸没法产生的压力衰减曲线与其他一维瞬态法产生的压力衰减曲线略有不同。这些差异开始证明，在可实现的实验条件下，对来自一个全浸试验的压力数据进行的分析除了能够测量其孔隙率外，还可以同时估算与圆柱状样品平行和垂直的表观渗透率。后续文章通过参数估计程序最终确定了此功能的证明，并通过概念验证研究提出了实验验证。该文章中对此进行了更详细的描述，参数估计器需要多个正向仿真来分析数据，从而可以最大程度地减少每次仿真的计算时间。