ASTM D7569-10
(Practice)Standard Practice for Determination of Gas Content of Coal-Direct Desorption Method
Standard Practice for Determination of Gas Content of Coal-Direct Desorption Method
SIGNIFICANCE AND USE
Canister desorption is a widely used technique to measure the gas content of coal. The gas content data when normalized to volume/weight and multiplied by coal mass is used to estimate the gas in place in an area around the cored well.
SCOPE
1.1 This practice describes methods for the direct determination of the gas content of coal by desorption using samples obtained by drill coring methods from the surface. It sets out guidelines for the equipment construction, sample preparation and testing procedure, and method of calculation.
1.2 Indirect methods for the determination of the gas content of coal (not covered in this practice) are based on either the gas absorption characteristics of coal under a given pressure and temperature condition or other empirical data that relate the gas content of coal to such other parameters as coal rank, depth of cover, or gas emission rate.
1.3 This practice covers the following two direct methods, which vary only in the time allowed for the gas to desorb from the core, or sidewall core, before final crushing:
1.3.1 The slow desorption method in which volumetric readings of gas content are taken frequently (for example, every 10 to 15 min) during the first few hours, followed by hourly measurements for several hours, and then measurements on 24-h intervals until no or very little gas is being desorbed for an extended period of time.
1.3.2 The fast desorption method in which after initial desorbed gas measurements to obtain data for lost gas calculations, the canister is opened and the sample is transferred to the coal crusher. The remaining gas volume is measured on a crushed sample.
1.4 This practice is confined to the direct method using core, or sidewall core obtained from drilling. The practice can be applied to drill cuttings samples; however, the use of cuttings is not recommended because the results may be misleading and are difficult to compare to the results obtained from core desorption. The interpretation of the results does not fall within the scope of the practice.
1.5 Units—The values stated in either SI units or inch-pound units are to be regarded separately as the standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D7569 − 10
StandardPractice for
Determination of Gas Content of Coal—Direct Desorption
Method
This standard is issued under the fixed designation D7569; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope values stated in each system may not be exact equivalents;
therefore,eachsystemshallbeusedindependentlyoftheother.
1.1 This practice describes methods for the direct determi-
Combining values from the two systems may result in noncon-
nation of the gas content of coal by desorption using samples
formance with the standard.
obtained by drill coring methods from the surface. It sets out
1.6 This standard does not purport to address all of the
guidelines for the equipment construction, sample preparation
safety concerns, if any, associated with its use. It is the
and testing procedure, and method of calculation.
responsibility of the user of this standard to establish appro-
1.2 Indirect methods for the determination of the gas con-
priate safety and health practices and determine the applica-
tentofcoal(notcoveredinthispractice)arebasedoneitherthe
bility of regulatory limitations prior to use.
gas absorption characteristics of coal under a given pressure
and temperature condition or other empirical data that relate
2. Referenced Documents
the gas content of coal to such other parameters as coal rank,
2.1 ASTM Standards:
depth of cover, or gas emission rate.
D121 Terminology of Coal and Coke
1.3 This practice covers the following two direct methods,
D167 Test Method for Apparent and True Specific Gravity
which vary only in the time allowed for the gas to desorb from
and Porosity of Lump Coke
the core, or sidewall core, before final crushing:
D1412 Test Method for Equilibrium Moisture of Coal at 96
1.3.1 The slow desorption method in which volumetric
to 97 Percent Relative Humidity and 30°C
readings of gas content are taken frequently (for example,
D2799 Test Method for Microscopical Determination of the
every 10 to 15 min) during the first few hours, followed by
Maceral Composition of Coal
hourly measurements for several hours, and then measure-
D3172 Practice for Proximate Analysis of Coal and Coke
ments on 24-h intervals until no or very little gas is being
D3173 Test Method for Moisture in the Analysis Sample of
desorbed for an extended period of time.
Coal and Coke
1.3.2 The fast desorption method in which after initial
D3174 Test Method forAsh in theAnalysis Sample of Coal
desorbed gas measurements to obtain data for lost gas
and Coke from Coal
calculations, the canister is opened and the sample is trans-
D3176 Practice for Ultimate Analysis of Coal and Coke
ferred to the coal crusher. The remaining gas volume is
D3180 Practice for Calculating Coal and Coke Analyses
measured on a crushed sample.
from As-Determined to Different Bases
1.4 Thispracticeisconfinedtothedirectmethodusingcore,
D3302 Test Method for Total Moisture in Coal
or sidewall core obtained from drilling. The practice can be
D5192 Practice for Collection of Coal Samples from Core
applied to drill cuttings samples; however, the use of cuttings
E1272 Specification for Laboratory Glass Graduated Cylin-
isnotrecommendedbecausetheresultsmaybemisleadingand
ders
are difficult to compare to the results obtained from core
2.2 Australian Standard:
desorption.Theinterpretationoftheresultsdoesnotfallwithin
AS 3980 Guide to the determination of gas content of
the scope of the practice.
coal—Direct desorption method
1.5 Units—The values stated in either SI units or inch-
pound units are to be regarded separately as the standard. The
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
This practice is under the jurisdiction of ASTM Committee D05 on Coal and Standards volume information, refer to the standard’s Document Summary page on
Coke and is the direct responsibility of Subcommittee D05.21 on Methods of the ASTM website.
Analysis. Available from Standards Australia Limited, 286 Sussex St., Sydney, NSW,
Current edition approved Sept. 1, 2010. Published October 2010. DOI: 10.1520/ 2000, Australia, GPO Box 476, Sydney, NSW, 2001 Australia or via the website:
D7569–10. www.standards.org.au.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7569 − 10
2.3 ISO Standard: Gas content is conventionally reported in units of cubic
3 3
ISO 6706 Plastics laboratory ware—Graduated measuring centimetres/gram (cm /g), cubic metres/tonne (m /ton), or
cylinders standard cubic feet/ton (scf/ton). (1)
2.4 DIN Standard:
3.1.9 continuous coring, v—referstocontinuouscoringwith
DIN 12681 Plastics laboratory ware—Graduated measuring
wireline recovery. (1)
cylinders
3.1.10 conventional core, n—“large” diameter core (8.9 cm
or 3.5 in. diameter or larger) in which the core barrel is
3. Terminology
recoveredtothesurfaceafterdrillingafixedintervalbypulling
3.1 Definitions:
the drill string. (1)
3.1.1 For additional definitions of terms used in this
practice, refer to Terminology D121. 3.1.11 core, n—in drilling, a cylindrical section of rock
(coal) that is usually 5 to 10 cm in diameter taken as part of the
3.1.2 absolute permeability, n—permeability of a rock to a
particular fluid when the rock is 100 % saturated with the interval penetrated by a core bit and brought to the surface for
geologic examination, representative sampling, and laboratory
flowing fluid. (1)
analyses. (D121, D5192)
3.1.3 absorbed gas, n—gas that is molecularly dissolved
within a liquid phase or has penetrated into the lattice structure 3.1.12 cuttings, n—in drilling, rock fragments that break
of a solid. (1) away because of the action of the drill bit and are transported
to the surface by the drilling circulation system (mud or air).
3.1.4 actual lost gas time, n—lost gas time determined from
3.1.12.1 Discussion—Cuttings may be screened and col-
the time at which the sample being recovered reaches a depth
lected from the circulation medium for lithologic characteriza-
where the hydrostatic pressure of the drilling fluid column
tion or analytical tests. (2)
equals the original (immediately before sampling) reservoir
pressureinthesampletothetimeatwhichthesampleissealed
3.1.13 delivery tube, n—flexible tube connecting a desorp-
in a desorption canister.
tion canister to a volumetric displacement apparatus. (1)
3.1.4.1 Discussion—Essentially, the actual lost gas time is
3.1.14 desorption, n—detachment of adsorbed molecules
the amount of time between when the core starts its trip to the
from an interfacial surface (see adsorption). (1)
surface and it is sealed in the canister. (1)
3.1.15 desorption data analysis software, n—software used
3.1.5 adsorption, n—attachment, through physical or
for analyzing desorption data. (1)
chemical bonding, of fluid phase molecules to an interfacial
surface. 3.1.16 desorption rate, n—volumetric rate at which gas
3.1.5.1 Discussion—The adsorbed phase molecules are se- desorbs from a sample. (1)
questered at the interfacial surface in a metastable equilibrium
3.1.17 diffusion, n—process whereby particles of liquids or
state, the stability of which is strongly affected by changes in
gases move from a region of higher to lower concentration
temperature and pressure. (1)
independent of the pressure gradient. (1)
3.1.6 adsorption isotherm, n—quantitative relationship, at
3.1.18 diffusivity, n—ratio of the diffusion coefficient to the
constant temperature, describing how the concentration of
square of a typical diffusion distance. (1)
adsorbed phase molecules at an interfacial surface varies as a
3.1.19 direct desorption method, n—method for represent-
function of increasing system pressure. (1)
ing desorption of gas from coal or other materials in which gas
3.1.7 as-received basis, n—analytical data calculated to the
storage as a result of adsorption is significant.
moisture condition of the sample as it arrived at the laboratory
3.1.19.1 Discussion—It mathematically presumes constant
and before any processing or conditioning.
temperature diffusion from a sphere initially at uniform gas
3.1.7.1 Discussion—If the sample has been maintained in a
concentration. The solution of the basic equation adopted
sealed state so that there has been no gain or loss, the
suggests that the measured desorbed gas volume is propor-
as-received basis is equivalent to the moisture basis as
tional to the square root of time since the start of desorption
sampled. (D3180, D5192, D1412, D3302)
(time zero). The direct method is the most widely used method
3.1.8 canister, n—container that can be sealed into which a
for estimating lost gas volume. (1)
coal sample is placed to allow desorption to occur.
3.1.20 dry, ash-free basis, n—datacalculatedtoatheoretical
3.1.8.1 Discussion—The reduction in pressure to atmo-
base of no moisture or ash associated with the sample.
spheric pressure (at surface) causes the sample to release gas
3.1.20.1 Discussion—Numerical values as established by
into the canister. By measuring the amount of gas released and
Test Methods D3173 and D3174 are used for converting the
the weight of the sample, the gas content can be determined.
as-determined data to a moisture- and ash-free basis. (D3180)
4 3.1.21 fast desorption method, n—after initial measure-
Available from the International Organization for Standardization (ISO), 1, rue
ments to obtain the basis for lost gas calculations, the canister
de Varembé, Case Postale 56, CH-1211 Geneva 20, Switzerland or via the website:
http://www.iso.org/.
is opened and the sample is transferred to a coal-crushing
Available from Deutsches Institut für Normung e. V., 10772 Berlin or via the
device that is modified so that the remaining desorbed gas
website: http://www2.din.de.
volume from the crushed coal sample can be measured.
The boldface numbers in parentheses refer to the list of references at the end of
this standard. (AS 3980)
D7569 − 10
3.1.22 free gas, n—unabsorbed gas within the pores and 3.1.35 mesopores, n—pores in the coal larger than 2 nm and
natural fractures. (1) less than 50 nm. (3)
3.1.36 micropores, n—pores with a width of less than 2 nm.
3.1.23 gas-in-place, n—amount of gas present in a seam or
an interval of discrete thickness or in multiple seams or (3)
intervals determined from the gas content, bulk density,
3.1.37 modified direct method, n—modification of the direct
thickness, and drainage area.
method by the U.S. Bureau of Mines according to Diamond
3.1.23.1 Discussion—Estimates of gas-in-place usually re-
and Levine (4) and Diamond and Schatzel (5) to account
flect total gas content, which in addition to methane, may
precisely for changes in the concentration of gaseous species
include others gases such as carbon dioxide or nitrogen. (1)
during desorption, with particular applications to situations in
which small amounts of gas are evolved. (1)
3.1.24 gas saturated, adv—state in which the gas content
(determined from direct or indirect desorption measurements)
3.1.38 quick connect fittings, n—pipe fittings designed for
is equal to the gas storage capacity (determined from
easy and rapid connection and disconnection.
isotherms). (1)
3.1.39 raw basis, n—basis for gas content calculation
3.1.25 gas storage capacity, n—maximum amount of gas or
wherebythegasvolumeisdividedbytheactualsampleweight
gas mixtures (normalized according to the relevant basis) that
regardless of the moisture content or the presence of non-coal
can be held by a sample at various reservoir pressures,
in the canister sample. (1)
reservoir temperature, and a specific moisture (water) content.
3.1.40 residual gas volume, n—volume of the total sorbed
(1)
gas that remains in the sample after desorption into a canister
3.1.26 head space volume, n—void space in a canister
has effectively ceased (after termination of canister desorp-
containing a sample.
tion).
3.1.26.1 Discussion—Canister desorption measurements are
3.1.40.1 Discussion—Residual gas volume, as defined and
corrected for the effect of expansion or contraction of gases in
reported, can be very different for slow desorption and fast
thecanisterheadspaceinresponsetotemperatureandpressure
desorption methods. Early termination of desorption followed
fluctuations. (1)
bysamplecrushingwillobviouslylowerdesorbedquantitiesof
3.1.27 indirect method for the determination of the gas gas and increase the residual values. Maceral composition,
content of coal, n—method based on either the gas absorption lithotype composition, and the coal bench being sampled may
characteristics of coal under a given pressure and temperature all affect permeability on small-scale samples. (1)
condition or other empirical data that relate the gas content of
3.1.41 sidewall core, n—small diameter core taken down-
coal to such other parameters as coal rank, depth of cover, or
hole by wireline methods using percussion or mechanical
gas emission rate.
methods to drill into the side of the borehole.
3.1.28 in-situ basis, adj—a basis in which gas content is
3.1.41.1 Discussion—The percussion method cores by ex-
determined from a plot of gas content versus bulk density
plosively firing hollow core barrels into a coal seam and then
(determined from open-hole high-resolution bulk density log
retrieving the coal plug to the surface. The mechanical method
data). (1)
uses hollow rotary drills to core into the coal seam and then
pull the core plugs back into the tool and then they are
3.1.29 isotherm (sorption isotherm), n—quantitative
retrieved.
relationship, at constant temperature, that describes how the
concentration of adsorbed phase molecules at an interfacial
3.1.42 slow desorption method, n—volumetric readings of
surface varies as a function of system pressure. (1)
canister gas content are taken frequently (for example, every
10 to 15 min) during the first few hours, followed by hourly
3.1.30 lost gas time, n—time between when the sample gas
measurements for several hours, and then measurements on
pressure falls below the reservoir pressure during sample
24-h intervals until no or very little gas is being desorbed for
recovery (time zero) and the time when the sample is sealed in
an extended period of time.
a desorption canister. (1)
3.1.42.1 Discussion—Some coals can desorb in excess of
3.1.31 lost gas volume, n—volume of gas that is released
one year and a desorption base line may be established with
from a sample (generally under condit
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