Full
XIA Zongli,born in 2000, a Ph.D. candidate at China university of Petroleum(Beijing),is engaged in sedimentology,reservoir geology and well logging geology. E-mail: zhongxiashiba@outlook.com.
Outline
The Kuqa Depression hosts extensively distributed Mesozoic coal-bearing strata,characterized by substantial coal seam thickness and relatively abundant deep coalbed methane(CBM)resources. This study focuses on the Jurassic Kezilenuer Formation coal-bearing strata of the Kuqa Depression. Relative to shallow CBM reservoirs,deep coal seams exhibit markedly complex geological characteristics—including well-developed partings,heterogeneous coal matrix structure,and coexistence of adsorbed and free gas phases—posing significant challenges for reliable logging-based gas content evaluation. Integrating core observations from deep coal intervals in the study area with conventional logging,borehole imaging,and nuclear magnetic resonance(NMR)logging data,this work systematically investigates the geological characteristics of deep coal rocks and develops a robust methodology for quantifying their gas content. Deep Jurassic coal rocks in the Kuqa Depression consistently display low natural gamma radiation,low bulk density,high electrical resistivity,high neutron porosity,and large acoustic transit time—distinctive petrophysical signatures corroborated by imaging logs,which reveal bright blocky and speckled textures. Macroscopically,coal seams of the Kezilenuer Formation are predominantly semi-bright to semi-dull,classified as medium-fixed-carbon,high-volatile,medium-low-ash,and ultra-low-moisture coals. Coal seams No.2 and No.3 within Member 4 of the Kezilenuer Formation represent the principal target intervals,with average thicknesses of 4.5 m and 6.2 m,respectively,and mean burial depths exceeding 4000 m. Imaging log analysis indicates that these deep coal rocks largely retain primary(undisturbed)structural integrity. Leveraging empirical correlations established between laboratory-measured gas composition/contents and corresponding logging response parameters,a region-specific logging evaluation model was developed for estimating both compositional parameters and total gas content in deep coal rocks. Calculated total gas contents range from 5.95 to 10.95 m3/t(mean: 9.5 m3/t),comprising an average adsorbed gas content of 7.12 m3/t and an average free gas content of 2.38 m3/t. Complementary analysis using the T1-T2 cross-plot derived from NMR logging further reveals that higher gas content is preferentially associated with intervals exhibiting elevated resistivity,higher fixed carbon content,and structurally stable coal matrices. Synthesizing coal seam identification,maceral and industrial component analyses,and quantitative gas content estimation,this study establishes an integrated evaluation framework—combining conventional logs,borehole imaging,and 2D NMR logging—for jointly assessing deep coalbed methane and shale gas potential,thereby supporting resource assessment,reserve estimation,and exploration decision-making.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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