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Title: Determination of Coal Permeability Using Pressure Transient Methods

Abstract

Coalbed methane is a significant natural resource in the Appalachian region. It is believed that coalbed methane production can be enhanced by injection of carbon dioxide into coalbeds. However, the influence of carbon dioxide injection on coal permeability is not yet well understood. Competitive sorption of carbon dioxide and methane gases onto coal is a known process. Laboratory experiments and limited field experience indicate that coal will swell during sorption of a gas and shrink during desorption of a gas. The swelling and shrinkage may change the permeability of the coal. In this study, the permeability of coal was determined by using carbon dioxide as the flowing fluid. Coal samples with different dimensions were prepared for laboratory permeability tests. Carbon dioxide was injected into the coal and the permeability was determined by using pressure transient methods. The confining pressure was variedto cover a wide range of depths. The permeability was also determined as a function of exposure time of carbon dioxide while the confining stress was kept constant. CT scans were taken before and after the introduction of carbon dioxide. Results show that the porosity and permeability of the coal matrix was very low. The paper presents experimental data andmore » theoretical aspects of the flow of carbon dioxide through a coal sample during pressure transient tests. The suitability of the pressure transient methods for determining permeability of coal during carbon dioxide injection is discussed in the paper.« less

Authors:
;  [1]; ; ; ;
  1. (West Virginia University, Morgantown, WV)
Publication Date:
Research Org.:
National Energy Technology Laboratory (NETL), Pittsburgh, PA, and Morgantown, WV
Sponsoring Org.:
USDOE - Office of Fossil Energy (FE)
OSTI Identifier:
915427
Report Number(s):
DOE/NETL-IR-2007-143
TRN: US200817%%511
DOE Contract Number:
None cited
Resource Type:
Conference
Resource Relation:
Conference: Sixth Annual Conference on Carbon Capture & Sequestration, Pittsburgh, PA, May 7-10, 2007; Related Information: Only publication is the attached poster
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; 02 PETROLEUM; 03 NATURAL GAS; CARBON; CARBON DIOXIDE; CARBON DIOXIDE INJECTION; COAL; COAL DEPOSITS; METHANE; PERMEABILITY; TRANSIENTS

Citation Formats

McLendon, T.R., Siriwardane, H., Haljasmaa, I.V., Bromhal, G.S., Soong, Y., and Irdi, G.A. Determination of Coal Permeability Using Pressure Transient Methods. United States: N. p., 2007. Web.
McLendon, T.R., Siriwardane, H., Haljasmaa, I.V., Bromhal, G.S., Soong, Y., & Irdi, G.A. Determination of Coal Permeability Using Pressure Transient Methods. United States.
McLendon, T.R., Siriwardane, H., Haljasmaa, I.V., Bromhal, G.S., Soong, Y., and Irdi, G.A. Tue . "Determination of Coal Permeability Using Pressure Transient Methods". United States. doi:. https://www.osti.gov/servlets/purl/915427.
@article{osti_915427,
title = {Determination of Coal Permeability Using Pressure Transient Methods},
author = {McLendon, T.R. and Siriwardane, H. and Haljasmaa, I.V. and Bromhal, G.S. and Soong, Y. and Irdi, G.A.},
abstractNote = {Coalbed methane is a significant natural resource in the Appalachian region. It is believed that coalbed methane production can be enhanced by injection of carbon dioxide into coalbeds. However, the influence of carbon dioxide injection on coal permeability is not yet well understood. Competitive sorption of carbon dioxide and methane gases onto coal is a known process. Laboratory experiments and limited field experience indicate that coal will swell during sorption of a gas and shrink during desorption of a gas. The swelling and shrinkage may change the permeability of the coal. In this study, the permeability of coal was determined by using carbon dioxide as the flowing fluid. Coal samples with different dimensions were prepared for laboratory permeability tests. Carbon dioxide was injected into the coal and the permeability was determined by using pressure transient methods. The confining pressure was variedto cover a wide range of depths. The permeability was also determined as a function of exposure time of carbon dioxide while the confining stress was kept constant. CT scans were taken before and after the introduction of carbon dioxide. Results show that the porosity and permeability of the coal matrix was very low. The paper presents experimental data and theoretical aspects of the flow of carbon dioxide through a coal sample during pressure transient tests. The suitability of the pressure transient methods for determining permeability of coal during carbon dioxide injection is discussed in the paper.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2007},
month = {Tue May 01 00:00:00 EDT 2007}
}

Conference:
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  • The permeability of coal samples from Pittsburgh Seam was determined using carbon dioxide as the flowing fluid. The confining pressure was varied to cover a wide range of depths. The permeability was determined as a function of exposure time of carbon dioxide while the confining stress was kept constant. The porosities of the coal samples were found to be very low and most of the samples had porosities less than 1%. The permeability of these coal samples was very low-less than 1μD. Since the objective of this study was to investigate the influence of CO 2 exposure on coal permeability,more » it was necessary to increase the initial permeability of the coal samples by introducing a fracture. A longitudinal fracture was induced mechanically, and CT scans were taken to ensure that the fracture was present throughout the sample and that the sample was not damaged otherwise during the process. In this study, the permeability of coal was determined by using pressure transient methods. Two types of pressure pulses were used: A-spike and Sine-6 pressure transients. It was first established that the permeability of fractured coal samples did not change with exposure time when an inert gas (Argon) was used as the fluid medium in the experiments. However, the permeability of coal samples decreased significantly when carbon dioxide was used as the fluid medium. This reduction can be attributed to the coal swelling phenomenon. The results show that the permeability reduction in fractured coal samples can be over 90% of the original value, and the exposure time for such reductions can range from 1.5 days up to a week, typically about 2 days under laboratory conditions. The permeability decreased significantly with the increase in confining pressure. The higher confining pressure appears to close internal fractures causing a reduction in permeability.« less
  • The purpose of this study is to summarize the theoretical background of methods which have been used to determine formation permeability, fracture length, and fracture conductivity in low-permeability, hydraulically fractured gas reservoirs. This summary is intended to emphasize the major strengths and weakness of the methods studied. These characteristics have not always been emphasized in the original literature and have, in some cases, remained obscure to the practicing engineer. This preprint is a companion work to SPE-7930, in which the experience in application of these techniques to problems arising in practice is discussed. Test analysis methods discussed include: (1) amore » method applicable only after a pseudo-radial flow pattern is developed in the reservoir, (2) a method applicable when linear flow dominates in the reservoir, (3) published type curves, with emphasis on those which include finite-conductivity fractures, (4) a modification of linear-flow techniques useful for finite-conductivity fractures, and (5) use of finite-difference reservoir simulators in a history matching mode. 10 references.« less
  • The formation vertical permeability is often the dominant reservoir parameter in the performance of water and/or gas coning into a well, gravity drainage of high relief reservoirs, and interlayer cross-flow in secondary recovery projects. The advantages of either a pulse test or analyzing the early transient pressure response of a constant rate test compared to previous techniques are simplicity of interpretation, short duration of test, and minimum interference from conditions some distance away from the test well. The pulse test has a further advantage over the constant rate test, because the rate does not have to be kept constant duringmore » the short flow period. The vertical permeability pulse test has been used to estimate the vertical permeability of a low permeability zone in the Fahud field, Oman.« less
  • Variograms for permeability are typically calculated using well log and core measurements, if they are calculated at all. Such procedures are inadequate to estimate variograms for horizontal permeability as they yield almost no information about the short lag structure of the variogram. A well test samples a much larger region of the reservoir than log and mm measurements and thus, well test responses are potential sources of data for estimating the horizontal permeability variogram. We established the feasibility of calculating this variogram from a single set of well test data. Here we summarize further research on estimating horizontal permeability variogramsmore » from well test data. Our major focus in this paper is on improving horizontal variogram estimates by combining responses from tests on a number of different wells. We also address a few issues related to variogram estimation from single well test data. All work presented here is based on simulated well test data using permeability distributions generated with an imposed correlation structure and level of heterogeneity.« less
  • In strongly vertically heterogeneous reservoirs, the oil flows to the well through the high permeability layers. Often in this kind of reservoirs, most of the original oil in place is stored in the low permeability layers, which are not contributing directly to the well production. This oil can only contribute to production if vertical communication occurs between low permeability layers and high permeability layers. Because the vertical permeability has a major impact on oil recovery, the evaluation of its uncertainty is a key factor for economic evaluation of the field. This paper demonstrates how uncertainties in vertical permeability were deducedmore » from pressure transient analysis on a field example in the Middle East. The classical multilayer analytical solution which represents crossflow between layers with the pseudo-steady state assumption was used. This paper highlights a practical method to compute the whole range of vertical permeabilities which honor the well test data. The use of these computed vertical permeabilities in reservoir simulation is discussed.« less