Experimental Investigation of Gas Dynamic Effects Using Nanoporous Synthetic Materials as Tight Rock Analogues

Abstract

To improve the understanding of gas transport processes in tight rocks (e.g., shales), systematic flow tests with different gases were conducted on artificial micro- to nanoporous analogue materials. Due to the rigidity of these systems, fluid-dynamic effects could be studied at elevated pressures without interference of poro-elastic effects. Flow tests with narrow capillaries did not reveal any viscosity anomaly in a confined space down to capillary diameters of 2 µm. Experiments with nanoporous ceramic disks (> 99% Al2O3) conducted at confining pressures from 10 to 50 MPa did not indicate any stress dependence of permeability coefficients. Analysis of the apparent permeability coefficients over a mean gas pressure range from 0.2 to 30.5 MPa showed essentially linear Klinkenberg trends with no indication of second-order slip flow. The Klinkenberg-corrected permeability coefficients measured with helium were consistently higher than those measured with all other gases under the same conditions. This “helium anomaly” was, however, less pronounced than the same effect observed in natural rocks, indicating that it is probably not related to fluid-dynamic effects but rather to gas–solid interactions (e.g., sorption). Permeability tests with CO2 on the nanoporous membrane show significant deviations from the linear Klinkenberg trend around the critical point. This is due to the drastic changes of the thermodynamic properties, in particular the isothermal compressibility, in this pressure and temperature range. Helium pycnometry, mercury intrusion porosimetry and low-pressure nitrogen sorption showed good agreement in terms of porosity (~ 28%) and the most prominent pore diameter (~ 68.5 nm).

An Early‐Time Solution of Pulse‐Decay Method for Permeability Measurement of Tight Rocks

“…3 of 14 used as testing fluid. Within the pressure range of the measurements (0.1-10 MPa), the compressibility factor 𝐴𝐴 𝐴𝐴 for helium is very close to the value of one, with an error smaller than 5% (McCarty & Arp, 1990;Nolte et al, 2021). Thus, the density 𝐴𝐴 𝐴𝐴 in Equation 3 could be replaced by the pressure 𝐴𝐴 𝐴𝐴 when multiplying both sides of Equation 3 by ∕ .…”

“…The scheme of the experimental setup is shown in Figure 8. A detailed description of the experimental setup can be found in our earlier publications (Gaus et al., 2019; Ghanizadeh et al., 2014; Nolte et al., 2021). The experimental protocol is briefly outlined as follows: The core sample was dried at 105 °C for at least 24 hr until weight constancy was achieved The core sample was put into the core holder, with two porous steel discs connected to its two ends to make the inlet and outlet flow uniform.…”

“…The scheme of the experimental setup is shown in Figure 8. A detailed description of the experimental setup can be found in our earlier publications (Gaus et al, 2019;Ghanizadeh et al, 2014;Nolte et al, 2021). The experimental protocol is briefly outlined as follows:…”

A modified pulse‐decay approach to simultaneously measure permeability and porosity of tight rocks

“…A detailed description of the experimental setup can be found in our previous studies. 29,30 Since applying a negative pulse in the downstream chamber and applying a positive pulse in the upstream chamber are mathematically equivalent, we only take the former as an example in the following part of the study. To keep the downstream pressure constant during the test, the downstream volume is chosen to be much larger than the sum of the pore volume and the volume of the upstream chamber, that is, V d ≫ V p + V u , or to be open to the atmosphere.…”

Performance Improvement of Glass Microfiber Based Thermal Transpiration Pump Using TPMS

“…He found slight pressure generated from these porous materials after applying steam on one side and water on another side of porous materials. Other porous materials were also investigated recently such as aerogel [ 9 ], zeolite [ 10 ], cellulose ester [ 11 ] and nanoporous ceramic [ 12 ]. All of these types of porous materials need to have small pore sizes and low thermal conductivity to increase temperature differences across the materials themselves.…”