BS ISO 4657:2022 pdf download.Assessment specification of coalbed methane resources
5.2.3 Drilling data
5.2.3.1 Mud logging data
Mud logging includes cuttings logging, drilling time logging, coring and gas logging. The deliverables include a comprehensive mud logging curve and a gas logging map.
5.2.3.2 Wireline logging data
The conventional wireline logging series to be used includes deep or shallow laterolog, microsphere focus logging, compensated density log, compensated neutron log, compensated acoustic log, natural potential log, natural gamma log and dual calliper log in CBM development.
The unconventional wireline logging series to be used includes acoustic imaging log, resistivity imaging log and nuclear magnetic resonance (NMR) imaging log in CBM development.
5.2.3.3 Well testing data
Fall-off testing in injection wells is generally conducted.
5.2.4 Laboratory test data
Laboratory test data mainly includes core description, coal structure analysis, bulk density, macerals of coal, proximate analysis of coal, elemental analysis, vitrinite reflectance, gas composition, gas content,and isothermal adsorption test. See Table 1 for the results and application for each item.
5.3 Geological conditions analysis
5.3.1 Determination of exploration degree
The exploration degree of the evaluation region shall be determined according to the in-depth analysis of coal field exploration, CBM exploration data and coal production status.
5.3.2 Geologic map compiling
On the basis of data collection, collation and analysis, the basic geologic maps shall be compiled for the evaluation of CBM resources, such as coal seam structure contour map, coal seam burial depth map,coal seam isopach map, stratigraphic correlation profile and CBM gas content map.
5.3.3 Comprehensive analysis
The geological condition analysis includes the regional tectonic characteristics, sedimentary characteristics, strata and coal seam distribution, coal characteristics and coal rank, coal reservoir characteristics (porosity, permeability, gas content, temperature, pressure, etc.), rock characteristics of the roof and floor of coal seam and hydrogeological characteristics. They provide a geological basis for the evaluation methods selection and key parameters value assignment.
5.4 CBM resource calculation
5.4.1 General
The volumetric method shall be used for resource calculation if there is adequacy of geological data which meets requirements of the calculation.
5.4.2 Principles for input parameters value assignment for volumetric method
5.4.2.1 General requirement
The input parameters used in the resource calculation shall be prudently verified on the basis of comparing their accuracy and representativeness, and the principles for value assignment shall be briefly described in the resource evaluation report.
5.4.2.2 Value assignment principles for gas-bearing area
“Gas-bearing area” refers to the region of coal seam distribution in the resource evaluation region.
Geological, drilling, logging, seismic and coal sample test data shall be fully utilized to comprehensively analyse the geometrical dimensions of coal seam distribution.
The boundary of the CBM reservoir shall be identified by fault, pinch, erosion, effective thickness of coal seams cut-off, gas content cut-off, gas weathering, spontaneous combustion or goaf.
The boundary of the mineral right and the natural geographical boundary shall also be considered.
5.4.2.3 Value assignment principles for effective thickness of coal seams
The effective thickness of the coal bed refers to the thickness of coal seams minus the gangue layer, also known as the “net thickness”. It can be determined by coring data or by electrical property cut-off of the coal seam.
The effective thickness of coal seams cut-off should be 0,5 m. Any individual seam with thickness (with gangue layer thicker than 0,1 m deducted, if any) less than 0,5 m shall be ignored.
The area-weighted average thickness taken by the area trade-off method shall be used.
5.4.2.4 Value assignment principles for coal density
The arithmetic average density of all coal samples measured in the laboratory shall be used.
5.4.2.5 Value assignment principles for CBM content
The CBM content of coal samples shall be determined in accordance with ISO 18871.
The cut-off of gas content on an air-dried basis should be 1,0 m 3 /t. It can be adjusted according to a different coal rank and, with the increase of coal rank, the cut-off of gas content can be increased appropriately.BS ISO 4657 pdf download.BS ISO 4657 pdf download
