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This paper presents a series of surface experimental simulations of methane-oriented underground coal gasification using hydrogen as gasification medium. The main aim of the experiments conducted was to evaluate the feasibility of methane-rich gas production through the in situ coal hydrogasification process. Two multi-day trials were carried out using large scale gasification facilities designed for ex situ experimental simulations of the underground coal gasification (UCG) process. Two different coals were investigated: the “Six Feet” semi-anthracite (Wales) and the “Wesoła" hard coal (Poland). The coal samples were extracted directly from the respective coal seams in the form of large blocks. The gasification tests were conducted in the artificial coal seams (0.41 × 0.41 × 3.05 m) under two distinct pressure regimes - 20 and 40 bar. The series of experiments conducted demonstrated that the physicochemical properties of coal (coal rank) considerably affect the hydrogasification process. For both gasification pressures applied, gas from “Six Feet” semi-anthracite was characterized by a higher content of methane. The average CH4 concentration for “Six Feet” experiment during the H2 stage was 24.12% at 20 bar and 27.03% at 40 bar. During the hydrogasification of “Wesoła" coal, CH4 concentration was 19.28% and 21.71% at 20 and 40 bar, respectively. The process was characterized by high stability and reproducibility of conditions favorable for methane formation in the whole sequence of gasification cycles. Although the feasibility of methane-rich gas production by underground hydrogasification was initially demonstrated, further techno-economic studies are necessary to assess the economic feasibility of methane production using this process.

This work presents the development of a 3D hybrid coupled dual continuum and discrete fracture model for simulating coupled flow, reaction and deformation processes relevant to fractured reservoirs with multiscale fracture system, e.g., coal and shale, efficiently and accurately. In this hybrid model, the natural fracture network and coal matrix are described together by a dual continuum approach and the large fractures are represented explicitly by the discrete fracture approach. A combination of different types of elements is used for spatial discretization. Large fractures are discretised with lower-dimensional interface elements and continuum domains with higher-dimensional elements. The coupling between the two models is achieved via the principle of superposition. To reduce computational time of simulations for complex and large-scale problems, a hybrid MPI/OpenMP parallel scheme is implemented in this work. The developed model is applied to investigate coupled thermal, hydraulic, and mechanical processes associated with CO2 sequestration and enhanced coalbed methane recovery. The results demonstrate capabilities of the model to adequately capture the effects of multiscale fracture system and their coupled behaviour during CO2 injection and methane recovery from coal reservoirs. Performance of the proposed parallelisation scheme was tested by comparing computation times of serial and parallel implementations. A good performance improvement was achieved, the speedup using parallelized scheme reaches up to about 10 times along with satisfactory scalability for considered application example. The findings of this work support developments and improvements of efficient advanced numerical models to study coupled THCM behaviour in fractured porous geomaterials.

Previous projects on CO2 storage in coal often reported the challenges associated with coal swelling and swelling induced loss of gas injectivity. Since coal seams are typically thin, commonly used vertical wells only intersect a target reservoir over a small contact area, placing constraints on CO2 injectivity in addition to those resulting from coal swelling. This leaves the storage reservoirs largely under-utilized and, therefore, questions the viability of this technology. To address the challenges/limitations of the current practice, a novel in-situ CO2 injection test is planned using horizontal injection wells in Mikolow, Poland. This paper presents the pre-operational simulation studies conducted to assist the design and operation of the in-situ test. An existing dual-porosity model that is built on a coupled thermo-hydro-chemical-mechanical (THCM) modelling framework is employed in this study. Sensitivity of the model parameters and validity of the model are tested. Several simulation scenarios are developed in reference to the selected test site for various horizontal well configurations and gas injection conditions. From the results and analyses, it is evident that by varying the coal-CO2 contact area via the length of the horizontal injection well, as well as the operating conditions including fixed pressure, and fixed rate injection scenarios, the targeted amount (between 1 to 10 tonnes) of CO2 can be injected into the seam without significant loss of permeability or injectivity, yielding sustained gas injection. Moreover, the spread of CO2 is predicted to be contained within the model domain suggesting no significant concern of spread exceeding the test area. Minister of Science and Higher Education entitled "PMW" in the years 2020-2023; (agreement No. 5144/FBWiS/2020/2). The ROCCS project has received funding from the Research Fund for Coal and Steel under Grant Agreement No. 899336.

Matric suctions of several compacted soil specimens of a low-plastic soil were measured using null-type axis-translation technique. The study showed that in general, the dynamically compacted specimens reached equilibrium sooner than the statically compacted specimens and exhibited greater matric suctions. For a given compaction type (dynamic or static), the influence of an increase in the dry density due to an increase in the compaction effort had practically negligible influence on the measured matric suctions. Comparison of the null-type test results with the suction-water content soil-water characteristic curves of the soil showed some disagreements particularly for matric suctions greater than 20 to 30 kPa. Continuity in the water phase between the soil water, the water in the ceramic disk, and the water in the compartment below the ceramic disk, was verified soon after the measurements of matric suction were completed by increasing the chamber air pressure and monitoring the corresponding water pressure increase below the ceramic disk. The test results clearly showed a lack of continuity in the water phase during the suction measurements. Use of various interface materials (viz., a wet filter paper, slurries prepared from the tested soil and a kaolinite) significantly improved the water phase continuity; however, reduced the matric suctions of the soil specimens tested.

Non isothermal moisture movement in unsaturated kaolin is investigated in a series of experiments. Vapour transfer is then empirically quantified, and its theoretical representation considered. A thermo-hydraulic cell is used to apply thermal and hydraulic gradients to confined specimens in a number of thermal gradient, thermal-hydraulic gradient, and isothermal-hydraulic tests. Transient measurements of the thermal regime are made, and end of test measurement of moisture content, porosity, and chemical composition from a number of identical tests run for different durations allow pseudo transient variations of these parameters to be established. In each of the tests, where a thermal gradient is applied, the accumulation of chloride ions in the hottest regions indicates a cyclic movement of vapour and liquid moisture. Estimated vapour fluxes are determined by consideration of overall moisture and conservative ion movements in the sealed thermal gradient tests. These vapour fluxes are then compared to those predicted by an established vapour flow theory, and a modification to this theory is proposed based on a variable enhancement factor.

(1981). Cost‐effectiveness Analysis as a Method of Assessing ‘A’ level Performance in Different Educational Establishments. Educational Studies: Vol. 7, No. 2, pp. 95-103.