Adsorption Factors in Enhanced Coal Bed Methane Recovery: A Review

Enhanced coal bed methane recovery using gas injection can provide increased methane extraction depending on the characteristics of the coal and the gas that is used. Accurate prediction of the extent of gas adsorption by coal are therefore important. Both experimental methods and modeling have been used to assess gas adsorption and its effects, including volumetric and gravimetric techniques, as well as the Ono–Kondo model and other numerical simulations. Thermodynamic parameters may be used to model adsorption on coal surfaces while adsorption isotherms can be used to predict adsorption on coal pores. In addition, density functional theory and grand canonical Monte Carlo methods may be employed. Complementary analytical techniques include Fourier transform infrared, Raman spectroscopy, XR diffraction, and 13C nuclear magnetic resonance spectroscopy. This review summarizes the cutting-edge research concerning the adsorption of CO2, N2, or mixture gas onto coal surfaces and into coal pores based on both experimental studies and simulations.

Emisiones de metano asociadas a la minería subterránea del carbón en el altiplano cundiboyacense (Colombia)

A raíz del Acuerdo de Paris sobre el cambio climático, Colombia se comprometió a medir y reportar las emisiones de gases de efecto invernadero (GEI), entre estas, las emisiones fugitivas de la minería del carbón. El país ha venido reportando las emisiones a partir de tablas internacionales (nivel 1 del Panel Intergubernamental del Cambio Climático - IPCC), pero en la presente propuesta se sugiere hacerlo a partir de los estudios de exploración de nivel 2 del metano de lecho de carbón (coal bed methane, CBM) utilizando equipos de desorción con canisters. En el altiplano cundiboyacense se revisaron los contenidos a partir de tablas internacionales y de estudios de CBM y se encontró que a partir del rango del carbón de nivel 1 (61,62 Gg de metano) las emisiones excedían los contenidos encontrados en mediciones directas de nivel 2 (16,47 Gg de metano) en más de 300 %. También se encontró que los niveles de emisiones equivalentes en toneladas de CO2 eran de 1.540.500 y 411.750 toneladas, en Boyacá y Cundinamarca, respectivamente. Los resultados evidenciaron que dado que los contenidos de gas metano asociados al carbón en las cuencas colombianas no son tan altos como los de los principales países productores de carbón, las emisiones de la extracción de carbón en el país fueron menores que las calculadas con factores de emisión internacionales. Por lo tanto, mientras no se midan las emisiones directamente en la ventilación, se deben utilizar los estudios de exploración de CBM para reportar emisiones, ya que con base en las tablas internacionales podrían estarse reportando más emisiones de GEI asociadas a la minería del carbón de las que realmente se están generando.

Pressure Transient Analysis for Horizontal Wells in Coal Bed Methane Reservoirs with Pressure-Sensitive Permeabilities

Coal bed methane (CBM) reservoirs are complex systems whose properties differ from those of conventional reservoirs. Coal seams are dual-porosity systems that comprise the porosities of the matrix and cleat system. Gas in the coal seams can be stored as free gas in the cleat system and as adsorbed gas in the porous medium. The flow mechanisms of the natural gas through the formation include desorption, diffusion, and Darcy’s flow regimes. The permeability of CBM reservoirs is more sensitive to pressure variations than conventional gas reservoirs. To study the flow behavior of CBM reservoirs it is mandatory to use a model that considers their unique characteristics. The objective of this study was to propose a physical and mathematical model of production performance for horizontal wells in CBM reservoirs whose permeability is dependent on pressure. A solution for the model was obtained by applying Pedrosa´s transformation, perturbation theory, Laplace transformation, the point source method, and Sthefest´s algorithm. The solution to this problem was validated with previous work thoroughly. The type curves of the model were built and the pressure transient behavior of the model was analyzed and discussed. The effects of several parameters on pressure behavior were also discussed.

The Rise of Non Conventional Energy Prompted the Reunderstanding and Division of Oil and Gas Migration in the Petroleum Industry

In recent years, with the development of coal bed methane, especially large-scale success shale oil and gas exploitation, People will not only in sedimentary basin energy re classified as conventional energy and non conventional energy, And the non conventional energy referred to an important aspect and a situation of tripartite confrontation of the conventional energy sources, new energy, In this paper, in the identity of non conventional energy in the future as a kind of new energy type, Analysis is made on the global and China's major non conventional energy, resources potential, exploration and exploitation of species status, Foundation and face geological theories and engineering problems on, Emphasis on non conventional energy and conventional energy relationship, Both belong to the Petroleum industry. Is called the non conventional energy, is compared with the conventional energy. Because, whether conventional or non conventional sources of energy, Basically are generated and preserved in the sedimentary basin, or that there is a close relationship with sedimentary basin. Coal bed methane, shale gas, oil sands, oil shale, tight oil and gas, it is called the non conventional energy. Compared with the conventional energy sources -- coal, oil, and gas. Obviously, there are many similarities between them. That is, all belong to the fossil energy, To form (coal) containing oil and gas basin. The formation, not only distribution and evolution of the basin development, And form, and conventional energy accumulation are closely linked, not separate. It can be said that most of the non conventional energy product belongs to the oil and gas in different periods, the same kind of energy at different stages, Research thinks, migration to bridge non conventional energy and conventional energy sources of oil and gas, Unconventional oil and gas is the inheritance and development of conventional oil and gas, Unconventional oil and gas is the extension and expansion of conventional oil and gas denotation, connotation .