Analysis of the Pressure-Pulse Propagation in Rock: a New Approach to Simultaneously Determine Permeability, Porosity, and Adsorption Capacity

Abstract

Permeability estimation from pressure-pulse decay method is complicated by two facts: (1) the decay curve often deviates from the single-exponential behavior in the early time period and (2) possible existence of gas adsorption. Both the two factors cause significant permeability error in most of pressure-pulse decay methods. In this paper, we first present a thorough analysis of pressure-pulse propagation process to reveal the mechanism behind the early time and later time behaviors of pressure decay curve. Inspired by the findings from these analyses, a new scaled pressure is proposed which can: (1) be easily used to distinguish the early time and later time data and (2) make the decay curves of all cases into a single 1:1 straight line for later time. A new data-proceeding method, which calculates the apparent porosity and permeability using the same set of measured data, is then developed. The new method could not only remove the effects of the adsorption on the permeability estimation, but also identify the apparent porosity as well as proper adsorption model and parameters. The proposed method is verified by comparing with true values and calculated values through numerical simulations that cover variations in typical rock properties (porosity, permeability, slippage, and adsorption) and the experiment configurations. It is found that the new method is accurate and reliable for all test cases, whereas the Brace's and Cui's approaches may cause permeability error in some cases. Finally, the new method has been successfully applied to real data measured in pressure-pulse decay experiments involving different types of rocks and gases.

A method for simultaneously determining axial permeability and transverse permeability of tight reservoir cores by canister degassing test

“…Figure 7 shows the schematic sketch of the PPD technique. [28][29][30][31] The sample is first in equilibrium and then opens the valve between the upstream chamber and the sample as well as the valve between the sample and the downstream chamber to let fluid flowing from the upstream chamber to the downstream chamber through the sample driven by the pressure difference. The axial permeability can then be estimated from the pressure pulse decay curve (the upstreamdownstream pressure difference with time) using mathematical solutions of the related flow problem.…”

“…Experimental permeabilities obtained from CDT tests (A) for the vertical sample. Experimental permeabilities obtained from CDT tests (B) for the horizontal sampleF I G U R E 7The schematic sketch of the pressure pulse decay technique [28][29][30][31]. The sample is first in equilibrium and then opens the valve between the upstream chamber and the sample to let fluid flowing from the upstream chamber to the downstream chamber through the sample driven by the pressure difference…”

Permeability model of fractured rock with consideration of elastic‐plastic deformation

“…The test ends when the upstream‐downstream pressure difference becomes very small. The sample permeability can then be determined from the pressure difference data using mathematical solutions of the related flow problem …”

“…The schematic sketch of the pressure pulse decay technique. The sample is first in equilibrium and then opens the valve between the upstream chamber and the sample to let fluid flowing from the upstream chamber to the downstream chamber through the sample driven by the pressure difference…”

Analysis of Internal Stress Distribution and Mechanics Characteristics of Pre-existing Cavity in Brittle Rock Under Triaxial Cyclic Loading

“…In the process of rock mass excavation and mineral mining (Yang et al, 2017;Wang et al, 2019;Zhang et al, 2019;Zhao et al, 2019b), an excavation damage zone will be formed in the surrounding rock within a certain range of the cave (Salehnia et al, 2015). In order to provide a theoretical basis for the stability and safety of rock masses in engineering contexts, physical experiments and scanning electron microscopy (SEM), Computed Tomography (CT), Acoustic emission (AE), and numerical simulation have been carried out on artificial jointed rock (Zhao et al, 2017b;Peng et al, 2019b;Zhao et al, 2019a) or rock-like materials (Zhao et al, 2016;Lin et al, 2019a).…”