A Model and Measurement Technique for Liquid Permeability of Tight Porous Media Based on the Steady-State Method

Abstract

Measuring tight-rock properties, in particular, permeability, is very important in a wide range of engineering applications from radioactive waste disposal and CO2 storage to production from unconventional hydrocarbon reservoirs. The steady-state method of permeability measurement is currently known to be impractical for tight rocks due to the long time needed to reach stabilized pressure and flowrate. In contrast to experimental results, the diffusivity equation predicts the steady state to happen much faster when a constant injection flowrate is used as a boundary condition. In this paper, we investigate the reason behind the inconsistency between the modeled and measured equilibrium time. We modify the boundary condition of the diffusivity equation based on an analogy from the well-testing models. We propose a semi-analytical solution for a more general diffusivity equation with a modified boundary condition. The results show that the main reason that makes the steady-state method time-consuming is the accumulator “storage effect”. When dealing with low-permeability rocks, the compressibility-induced flowrate, which is pressure-dependent, could be in the order of pump flowrate and makes the permeability measurement time-consuming. We modify the conventional coreflooding device to reduce the time of permeability measurement, making the steady-state method practical for tight-rock samples. The modified device is used to measure the permeability of a tight-rock sample, and the model can match the measured data with a very good accuracy. Reducing the volume of the accumulator vessel from 500 cc to around 10 cc causes a 50-fold decrease in the time required for steady-state establishment.

Liquid Permeability Determination from Vacuum Imbibition in Tight/Shale Core Plugs

“…Therefore, the estimated brine permeability values from the new method for these four samples are 28.3, 28.5, 86.7, and 94.0% smaller than the slip-corrected gas permeability, respectively, qualitatively consistent with the previous literature report that water permeability was several times to 1 order of magnitude lower than gas permeability . For the M1 and M2 core plugs under vacuum conditions, the liquid and gas permeability differences are interpreted to be caused by different boundary conditions and transport mechanisms. , In contrast, for the M3 and M4 core plugs under nonvacuum conditions, gas can be trapped behind the imbibition front due to gas–brine countercurrent flow (which will reduce the capillary pressure), while gas can be compressed in front of the imbibition front (which will increase the gas resistance to flow , ). However, neither gas trapping nor the resistance mechanism was considered in the modified Lucas–Washburn model.…”

A Laboratory Protocol to Evaluate Effective Permeability Alteration by Adding Surfactants in Fracturing Fluids

“…This effect is significant in low-permeability rocks, requiring time for flow rates to equalize. The new design reduces the “storage effect” from the accumulator by significantly decreasing the accumulator volume by 50-fold, to ∼10 cc, and reducing the dead volume inside the core holder . These modifications minimize the impact of fluid compressibility and volume changes on the measurement time.…”

“…The new design reduces the "storage effect" from the accumulator by significantly decreasing the accumulator volume by 50-fold, to ∼10 cc, and reducing the dead volume inside the core holder. 32 These modifications minimize the impact of fluid compressibility and volume changes on the measurement time. The process involves injecting oil at four distinct flow rates: 0.06, 0.09, 0.12, and 0.15 cc/h.…”

Study on Permeability Calculation Method Based on J Function and Fractal Theory

“…Sander et al (2017) introduced an experimental method for determining the rock permeability and compared the advantages and disadvantages of steady‐state methods and non‐steady‐state methods in detail. Many scholars have introduced in detail the methods of measuring permeability by non‐steady‐state (Sigmund and McCaffery 1979; Toth et al 2001; Choi et al 2020) and steady‐state methods (Zamirian et al 2014; Nazari Moghaddam and Jamiolahmady 2019; Yousefi and Dehghanpour 2022). The second is the indirect method which determines permeability by calculation (Burdine 1953; Pape et al 1998; Li and Horne 2005; Mohammadmoradi and Kantzas 2016; Srisutthiyakorn and Mavko 2017; Chai and Li 2020; Li et al 2020).…”