Variable gas saturation in coalbed methane reservoirs of the Black Warrior Basin: Implications for exploration and production

Pashin, Jack C.

doi:10.1016/j.coal.2009.10.017

Cited by 110 publications

(49 citation statements)

References 22 publications

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“…These two local folds bring the coal seams to the surface, where the reservoir pressure is relieved and where the coal seams can accept meteoric waters. Structural deformation in the general area has significant effect on the performance of coalbed methane reservoirs, the hydrodynamics in the area, and on the pressure gradients within the coal reservoirs with varying distance to these deformations (Pashin, 2007;Groshong et al, 2009;Pashin, 2010). The particular study area of this paper is approximately 5 miles from the main thrust fault and from the Blue Creek anticline and syncline (Fig.…”

Section: A Brief Description Of the Black Warrior Basin And Upper Potmentioning

confidence: 99%

Production history matching to determine reservoir properties of important coal groups in the Upper Pottsville formation, Brookwood and Oak Grove fields, Black Warrior Basin, Alabama

Karacan

2013

Journal of Natural Gas Science and Engineering

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The Black Warrior Basin of Alabama is one of the most important coal mining and coalbed methane production areas in the United States. Methane control efforts through degasification that started almost 25 years ago for the sole purpose of ensuring mining safety resulted in more than 5000 coalbed methane wells distributed within various fields throughout the basin. The wells are completed mostly in the Pratt, Mary Lee, and Black Creek coal groups of the Upper Pottsville formation and present a unique opportunity to understand methane reservoir properties of these coals and to improve their degasification performances.The Brookwood and Oak Grove fields in the Black Warrior Basin are probably two of the most important fields in the basin due to current longwall coal mining activities. In this work, methane and water productions of 92 vertical wellbores drilled, some completed 20 years ago, over a current large coal mine district located in these two fields, were analyzed by history matching techniques. The boreholes were completed at the Mary Lee coal group, or at combinations of the Pratt, Mary Lee, and Black Creek groups. History matching models were prepared and performed according to properties of each coal group.Decline curve analyses showed that effective exponential decline rates of the wells were between 2% and 25% per year. Results of production history matching showed, although they varied by coal group, that pressure decreased as much as 80% to nearly 25 psi in some areas and resulted in corresponding decreases in methane content. Water saturation in coals decreased from 100% to between 20 and 80%, improving gas relative permeabilities to as much as 0.8. As a result of primary depletion, permeability of coal seams increased between 10 and 40% compared to their original permeability, which varied between 1 and 10 md depending on depth and coal seam. These results not only can be used for diagnostic and interpretation purposes, but can be used as parameter distributions in probabilistic simulations, as illustrated in the last section of this paper. They can also be used in conjunction with spatial modeling and geological considerations to calculate potential methane emissions in operating mines.

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Section: A Brief Description Of the Black Warrior Basin And Upper Potmentioning

confidence: 99%

Production history matching to determine reservoir properties of important coal groups in the Upper Pottsville formation, Brookwood and Oak Grove fields, Black Warrior Basin, Alabama

Karacan

2013

Journal of Natural Gas Science and Engineering

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“…The Black Warrior basin contains numerous northwest striking normal faults and joints which form horst and graben structures with displacements as much as 400 ft (McFall et al 1986). Structural deformation in the general area is known to have a significant effect on the performance of coalbed methane wells, mining emissions, and hydrodynamics (Pashin 2007;Groshong and Pashin 2009;Pashin 2010). The majority of the Black Warrior basin coal-bearing strata of economic value are in the Pennsylvanian age Pottsville formation.…”

Section: Mary Lee Coal Group Of the Black Warrior Basin And The Specimentioning

confidence: 99%

Time-Lapse Analysis of Methane Quantity in the Mary Lee Group of Coal Seams Using Filter-Based Multiple-Point Geostatistical Simulation

Karacan

Olea²

2013

Math Geosci

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Coal seam degasification and its success are important for controlling methane, and thus for the health and safety of coal miners. During the course of degasification, properties of coal seams change. Thus, the changes in coal reservoir conditions and in-place gas content as well as methane emission potential into mines should be evaluated by examining time-dependent changes and the presence of major heterogeneities and geological discontinuities in the field. In this work, timelapsed reservoir and fluid storage properties of the New Castle coal seam, Mary Lee/Blue Creek seam, and Jagger seam of Black Warrior Basin, Alabama, were determined from gas and water production history matching and production forecasting of vertical degasification wellbores. These properties were combined with isotherm and other important data to compute gas-in-place (GIP) and its change with time at borehole locations. Time-lapsed training images (TIs) of GIP and GIP difference corresponding to each coal and date were generated by using these point-wise data and Voronoi decomposition on the TI grid, which included faults as discontinuities for expansion of Voronoi regions. Filter-based multiple-point geostatistical simulations, which were preferred in this study due to anisotropies and discontinuities in the area, were used to predict time-lapsed GIP distributions within the study area. Performed simulations were used for mapping spatial timelapsed methane quantities as well as their uncertainties within the study area.The systematic approach presented in this paper is the first time in literature that history matching, TIs of GIPs and filter simulations are used for degasification performance evaluation and for assessing GIP for mining safety. Results from this study showed that using production history matching of coalbed methane wells to determine time-lapsed reservoir data could be used to compute spatial GIP and representative GIP TIs generated through Voronoi decomposition. Furthermore, performing filter simulations using point-wise data and TIs could be used to predict methane quantity in coal seams subjected to degasification. During the course of the study, it was shown that the material balance of gas produced by wellbores and the GIP reductions in coal seams predicted using filter simulations compared very well, showing the success of filter simulations for continuous variables in this case study. Quantitative results from filter simulations Correspondence to: C. Özgen Karacan, cok6@cdc.gov. HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript of GIP within the studied area briefly showed that GIP was reduced from an initial ~73 Bcf (median) to ~46 Bcf (2011), representing a 37 % decrease and varying spatially through degasification. It is forecasted that there will be an additional ~2 Bcf reduction in methane quantity between 2011 and 2015. This study and presented results showed that the applied methodology and utilized techniques can be used to map GIP and its change within coal...

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“…Coal seam is the fundamental for CBM accumulation [7] . Under the same conditions, the greater the thickness of the coal, the more abundant gas source with the stronger the ability of gas supply, which is favorable to the higher gas production.…”

Section: Thicknessmentioning

confidence: 99%

High production indexes and key factors influencing coalbed methane (CBM) horizontal well productivity

Yang¹,

Tao²,

Yang³

et al. 2016

Proceedings of the 2016 5th International Conference on Energy and Environmental Protection (ICEEP 2016)

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Abstract:To evaluate the development effects systematically, the coalbed methane (CBM) production performance of 58 horizontal wells in the Fanzhuang block of the Qinshui Basin was tracked and correlations between the gas rate per 100 m and the influencing factors were discussed by single and multiple factor analysis. The grey correlation analysis (GRA) was then applied to quantitatively evaluate the key geological factors influencing CBM horizontal well productivity. The results show that the order of geological factors influencing horizontal well productivity is burial depth, gas production capacity (C), gas production potential (P), ratio of critical desorption pressure to initial reservoir pressure (p c /p i ), gas content, and thickness, where the gas production potential and capacity can reflect the comprehensive impacts of thickness, gas content, and permeability. The larger the gas production potential or capacity is, the better the gas productivity is. The high production indexes are the depth of 300~500m, p c /p i >0.6, P>130m 4 /t, C>60 mD×m 4 /t, and far away from the faults.

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Variable gas saturation in coalbed methane reservoirs of the Black Warrior Basin: Implications for exploration and production

Cited by 110 publications

References 22 publications

Production history matching to determine reservoir properties of important coal groups in the Upper Pottsville formation, Brookwood and Oak Grove fields, Black Warrior Basin, Alabama

Production history matching to determine reservoir properties of important coal groups in the Upper Pottsville formation, Brookwood and Oak Grove fields, Black Warrior Basin, Alabama

Time-Lapse Analysis of Methane Quantity in the Mary Lee Group of Coal Seams Using Filter-Based Multiple-Point Geostatistical Simulation

High production indexes and key factors influencing coalbed methane (CBM) horizontal well productivity

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