Predicting production performance of CBM reservoirs

“…How to define the dividing points becomes a key problem once the classification scheme is determined. Dimensionless treatment of production data is widely used to conventional oil/gas and CBM production analysis due to the elimination of the influence of dimension on data analysis (Clarkson et al 2008;Aminian and Ameri 2009;Freeman et al 2013). Hence, this paper uses the dimensionless method to process gas and water production data.…”

Section: Cbm Well Production Stages Divisionmentioning

confidence: 99%

Characteristics and control mechanisms of coalbed permeability change in various gas production stages

et al. 2015

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According to dimensionless analysis of the coalbed methane (CBM) production data of Fanzhuang block in southern Qinshui basin, the dimensionless gas production rate is calculated to quantitatively divide the CBM well production process into four stages, i.e., drainage stage, unstable gas production stage, stable gas production stage, and gas production decline stage. By the material balance method, the coal reservoir permeability change in different stages is quantitatively characterized. The characteristics and control mechanisms of change in coalbed permeability (CICP) during different production stages are concluded on five aspects, i.e., permeability trend variation, controlling mechanism, system energy, phase state compositions, and production performance. The study reveals that CICP is characterized by first decline, then recovery, and finally by increase and is controlled directly by effective stress and matrix shrinkage effects. Further, the duration and intensity of the matrix shrinkage effect are inherently controlled by adsorption and desorption features.

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“…If there are no producing wells in the field, proven techniques to determine coal reservoir properties include laboratory analyses (Gash, 1991;Saulsberry et al, 1996), geophysical logs (Li et al, 2011), and well testing methods (Aminian and Ameri, 2009;Nie et al, 2012). The major problem is, however, that it is not easy to determine reservoir properties of coal seams and they may be quite variable within the coal seam, even within relatively short distances.…”

Section: Significance and Objectivementioning

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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Predicting production performance of CBM reservoirs

Cited by 94 publications

References 9 publications

A comprehensive model to history match and predict gas/water production from coal seams

A comprehensive model to history match and predict gas/water production from coal seams

Characteristics and control mechanisms of coalbed permeability change in various gas production stages

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

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