A simplified pulse decay method (PDM) with only a single downstream reservoir is proposed to replicate the in situ conditions for reservoir fluid flow, where the pore pressure at any location declines as production continues. The proposed PDM also allows determining the effective porosity and permeability for the core sample under replicated in situ conditions. A mathematical model is firstly established to closely represent the experimental design and verify the feasibility of the method. The analytical solutions of the model are derived to calculate the effective sample porosity and permeability. A series of experiments are then conducted under triaxial stress condition, and a detailed comparison is also made between the PDMs with a single upstream reservoir and a single downstream reservoir. The experimental results showed that accurate measurements on effective sample porosity and permeability can be achieved by the single downstream reservoir PDM due to its capability of better replicating the in situ fluid flow behavior, which extends the application of the transient technique. It is also found that the pore pressure along the sample changes linearly, and its gradient varies with time, indicating the applicability of the single‐reservoir PDMs in permeability determination. This method also lays a foundation for studying flow behavior when a second fluid phase evolves during pressure decline, which occurs in many reservoirs.

中文翻译：

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确定致密地层中孔隙率和渗透率的简化瞬态技术：数值模拟和实验验证

提出了一种仅具有一个下游储层的简化脉冲衰减方法（PDM），以复制储层流体流动的原位条件，其中随着生产的继续，任何位置的孔隙压力都会下降。拟议的PDM还可以确定原位复制条件下岩心样品的有效孔隙率和渗透率。首先建立数学模型，以紧密地表示实验设计并验证该方法的可行性。导出模型的解析解以计算有效的样品孔隙率和渗透率。然后在三轴应力条件下进行了一系列实验，并对具有单个上游储层和单个下游储层的PDM之间进行了详细的比较。实验结果表明，由于单个下游储层PDM能够更好地复制原位流体流动行为，因此可以通过单个下游储层PDM进行有效样品孔隙率和渗透率的准确测量，从而扩展了瞬态技术的应用范围。还发现沿样品的孔隙压力呈线性变化，并且其梯度随时间变化，这表明单储层PDM在渗透率测定中的适用性。该方法也为研究在许多储层中发生的压力下降过程中第二流体相演化时的流动行为奠定了基础。扩展了瞬态技术的应用。还发现沿样品的孔隙压力呈线性变化，并且其梯度随时间变化，这表明单储层PDM在渗透率测定中的适用性。该方法也为研究在许多储层中发生的压力下降过程中第二流体相演化时的流动行为奠定了基础。扩展了瞬态技术的应用。还发现沿样品的孔隙压力呈线性变化，并且其梯度随时间变化，这表明单储层PDM在渗透率测定中的适用性。该方法还为研究在许多储层中发生的压力下降过程中第二流体相演化时的流动行为奠定了基础。