Quantitative Evaluation of Coal Seam Gas Content Estimate Accuracy

Mavor, Matthew P.; Pratt, T.; Nelson, Charles A.

doi:10.2523/29577-ms

Cited by 5 publications

(14 citation statements)

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“…11,22 Finally, quantitative, comparisons were made between the reservoir property values obtained by commonly used analysis procedures and the benchmark reservoir property values. [11][12][13][14][16][17][18][19][20][21] These analyses identified six major sources of errors in coalbed reservoir property and gas-in-place values.…”

Section: Major Sources Of Gas-in-place Errorsmentioning

confidence: 99%

“…In general, compositional analysis data from reservoir samples having a broad range of mineral matter content are needed to accurately determine the average in-situ properties. 12,16,19,20 A common practice in coalbed reservoir gas-in-place analysis is to use a rule-of-thumb value of 1.32 to 1.36 g/cm 3 for the in-situ reservoir rock density. 1,6,7 For vitrinite-rich bituminous rank coal, the organic matter density is about 1.295 g/cm 3 and the mineral matter density is about 2.497 g/cm 3 .…”

Section: In-situ Densitymentioning

confidence: 99%

“…For example, an in-situ adsorbed methane content of 400 scf/ton increases the density of bulk coal organic matter by only 0.010 g/cm 3 or 0.8%. 12,20 Moisture content affects the coal density. The moisture content varies inversely as a function of coal rank.…”

Section: In-situ Densitymentioning

confidence: 99%

“…The inaccurate determination of this reservoir property is commonly the single largest source of gas-in-place analysis error. [11][12][13][14][16][17][18][19][20][21] The two methods commonly used to determine the total in-situ gas content are pressure coring and the direct method. 15,20 Both methods have some inherent shortcomings.…”

Section: In-situ Gas Contentmentioning

confidence: 99%

“…1,9,10 This paper presents results from case study evaluations of the accuracy of commonly used coalbed reservoir property analysis methods. [11][12][13][14][15][16][17][18][19][20][21] Gas-In-Place Analysis Gas-in-place volume is the total amount of gas stored within a specific, bulk reservoir rock volume. Four physical reservoir properties are needed to calculate the gas-in-place volume.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Coalbed Reservoir Property Analysis Methods on Gas-In-Place Estimates

Nelson

1999

Proceedings of SPE Eastern Regional Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAccurately determining the gas-in-place volume is a crucial element of coalbed gas resource and reservoir evaluation. Different reservoir property analysis methods can yield very different gas resource and gas-in-place values. This paper presents results from evaluations of the accuracy of commonly used reservoir property analysis methods. Many commonly used analysis methods were found to have inherent shortcomings that can result in large (50% or greater) underestimation error in the gas-in-place value. Six major sources of error are: (1) basing the reservoir volume on the assumption that the coalbed reservoir thickness and lateral continuity are invariant, (2) using 1.75 g/cm 3 as the maximum log density value for determining the gross reservoir thickness, (3) using 1.32 to 1.36 g/cm 3 for the in-situ density of coalbed reservoirs, (4) basing the in-situ gas content on gas desorption data obtained at ambient temperature conditions, (5) basing the in-situ gas content on gas desorption data obtained from drill cuttings, and (6) basing the in-situ gas content on the assumption that the residual gas volume is negligible. Because these six error prone analysis practices have been so widely used in the past there may be significant potential for large gas-in-place and reserve estimate gains in many existing coalbed gas fields.

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Section: Major Sources Of Gas-in-place Errorsmentioning

confidence: 99%

Section: In-situ Densitymentioning

confidence: 99%

Section: In-situ Densitymentioning

confidence: 99%

Section: In-situ Gas Contentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of Coalbed Reservoir Property Analysis Methods on Gas-In-Place Estimates

Nelson

1999

Proceedings of SPE Eastern Regional Conference and Exhibition

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Sequestration of Carbon Dioxide in Coal with Enhanced Coalbed Methane RecoveryA Review

et al. 2005

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This article reviews the storage of captured CO2 in coal seams. Other geologic formations, such as depleted petroleum reservoirs, deep saline aquifers and others have received considerable attention as sites for sequestering CO2. This review focuses on geologic sequestration of CO2 in unmineable coalbeds as the geologic host. Key issues for geologic sequestration include potential storage capacity, the storage integrity of the geologic host, and the chemical and physical processes initiated by the deep underground injection of CO2. The review topics include (i) the estimated CO2 storage capacity of coal, along with the estimated amount and composition of coalbed gas; (ii) an evaluation of the coal seam properties relevant to CO2 sequestration, such as density, surface area, porosity, diffusion, permeability, transport, rank, adsorption/desorption, shrinkage/swelling, and thermochemical reactions; and (iii) a treatment of how coalbed methane (CBM) recovery and CO2-enhanced coalbed methane (ECBM) recovery are performed (in addition, the use of adsorption/desorption isotherms, injection well characterization, and gas injection are described, as well as reservoir screening criteria and field tests operating in the United States and abroad); (iv) leak detection using direct measurements, chemical tracers, and seismic monitoring; (v) economic considerations using CO2 injection, flue gas injection, and predictive tools for CO2 capture/sequestration decisions; (vi) environmental safety and health (ES&H) aspects of CO2-enhanced coalbed methane/sequestration, hydrodynamic flow through the coal seam, accurate gas inventory, ES&H aspects of produced water and practices relative to ECBM recovery/sequestration; (vii) an initial set of working hypotheses concerning the chemical, physical, and thermodynamic events initiated when CO2 is injected into a coalbed; and (viii) a discussion of gaps in our knowledge base that will require further research and development. Further development is clearly required to improve the technology and economics while decreasing the risks and hazards of sequestration technology. These concerns include leakage to the surface, induced seismic activity, and long-term monitoring to verify the storage integrity. However, these concerns should not overshadow the major advances of an emerging greenhouse gas control technology that are reviewed in this paper.

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Effects of Coalbed Reservoir Property Analysis Methods on Gas-In-Place Estimates

Nelson

1999

SPE Eastern Regional Meeting

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Accurately determining the gas-in-place volume is a crucial element of coalbed gas resource and reservoir evaluation. Different reservoir property analysis methods can yield very different gas resource and gas-in-place values. This paper presents results from evaluations of the accuracy of commonly used reservoir property analysis methods. Many commonly used analysis methods were found to have inherent shortcomings that can result in large (50% or greater) underestimation error in the gas-in-place value. Six major sources of error are:basing the reservoir volume on the assumption that the coalbed reservoir thickness and lateral continuity are invariant,using 1.75 g/cm3 as the maximum log density value for determining the gross reservoir thickness,using 1.32 to 1.36 g/cm3 for the in-situ density of coalbed reservoirs,basing the in-situ gas content on gas desorption data obtained at ambient temperature conditions,basing the in-situ gas content on gas desorption data obtained from drill cuttings, andbasing the in-situ gas content on the assumption that the residual gas volume is negligible. Because these six error prone analysis practices have been so widely used in the past there may be significant potential for large gas-in-place and reserve estimate gains in many existing coalbed gas fields.

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Quantitative Evaluation of Coal Seam Gas Content Estimate Accuracy

Cited by 5 publications

References 0 publications

Effects of Coalbed Reservoir Property Analysis Methods on Gas-In-Place Estimates

Effects of Coalbed Reservoir Property Analysis Methods on Gas-In-Place Estimates

Sequestration of Carbon Dioxide in Coal with Enhanced Coalbed Methane RecoveryA Review

Effects of Coalbed Reservoir Property Analysis Methods on Gas-In-Place Estimates

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