Competitive Methane Desorption by Supercritical CO2 Injection in Coal

Abstract

A large diameter (∼70 mm) dry coal sample was used to study the competitive displacement of CH 4 by injection of supercritical CO 2 , and CO 2 -CH 4 counter-diffusion in coal matrix. During the test, a staged loading procedure, which allows the calibration of the key reservoir modelling parameters in a sequential and progressive manner, was employed. The core-flooding test was history matched using an Enhanced Coalbed Methane (ECBM) simulator, in which Fick's Law for mixed gas diffusion and the extended Langmuir equations are implemented. The system pressure rise during the two loading stages and the CO 2 breakthrough time in the final production stage were matched by using the pair of constant sorption times (9 and 3.2 days) for CH 4 and CO 2 , respectively. The corresponding diffusion coefficients for CH 4 and CO 2 were estimated to be 1.6 × 10 −12 and 4.6 × 10 −12 m 2 /s, respectively. Comparison was made with published gas diffusion coefficients for dry ground samples (ranging from <0.063 to ∼3 mm) of the same coal at relatively low pressures (<4 MPa). The CO 2 /CH 4 gas diffusion coefficient ratio was well within the reported range (2-3), whereas the CH 4 diffusion coefficient obtained from history matching of the core-flooding test is approximately 15 times smaller than that arrived by curve-fitting the measured sorption uptake rate using a unipore diffusion model. The calibrated model prediction of the effluent gas composition was in good agreement with the test data for CO 2 mole fraction of up to 20%.

Complex evolution of coal permeability during CO2 injection under variable temperatures

“…Gas diffuses faster in the coal matrix under the non-isothermal condition due to the heat convection between the injected CO 2 and the coal, which accelerates the gas flow and shortens the time for the whole system to get equilibrium (Shi et al, 2008). Normally the switch from permeability reduction to recovery is very quick as the injection temperature is high.…”

Stability for implicit–explicit schemes for non-equilibrium kinetic systems in weighted spaces with symmetrization

“…In this section we develop the applications which motivate (2) and provide details on its abstract setup, in particular on the properties of L as they follow for the special cases of (1) under assumed boundary conditions. Our presentation of the model follows the literature on coalbed methane adsorption [9,10,11] where (1) arises directly, and finite volumes are used; see also our expository work in [12]. In Section 2.3 we discuss a particular direction in which (2) is reduced to a single equation; this is discussed in [5] under initial equilibrium assumption.…”

Effects of Coal Deformation on Different-Phase CO2 Permeability in Sub-Bituminous Coal: An Experimental Investigation

“…Since carbon dioxide (CO 2 ) is one of the leading greenhouse gases, many researchers are trying to find the appropriate methods to capture and store anthropogenic CO 2 emissions [1,2]. CO 2 sequestration in deep un-minable coal seams is currently identified as one of the promising solutions to reduce CO 2 emissions due to its potential large-scale storage capacity [3,4]. According to Gale's estimation [5], it will take less than $110 per ton of CO 2 sequestration in coal seams if overall 148 Gt of CO 2 could be stored in worldwide coal basins.…”