Genesis and accumulation mechanism of low rank coalbed methane in gas-rich depressions of Erlian Basin
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摘要: 内蒙古低阶煤煤层气资源丰富，煤层气成因与成藏机制研究对低阶煤煤层气资源选区评价至关重要。以二连盆地重点富气凹陷低阶煤煤层气为研究目标，利用煤层气组分、碳/氢同位素、煤层水水质、氢/氧同位素及放射性同位素3H和14C测试等多种实验手段，分析煤层气、水地球化学特征，揭示低阶煤煤层气成因来源及成藏机制。结果表明，二连盆地煤层气组分以甲烷为主，均为干气，其中甲烷体积分数随埋深增加而增大，CO2体积分数随埋深增加呈先增加后降低趋势，在300~500 m范围出现高值区。甲烷碳、氢同位素普遍偏轻，δ13C (CH4)分布在−70.3‰~−48.0‰，δD (CH4)分布在−285.5‰~−189.0‰，δ13C (CO2)在−37.6‰~1.94‰变化。煤层水化学类型主要为HCO3-Na型和Cl·HCO3-Na型，现今煤层水体环境较为稳定，水动力较弱，煤层水表观年龄在1 020~47 490 a，主要来源于第四纪大气降水，没有或较少有现今地表水补给。二连盆地煤层气主要为原生生物成因气，混有少量早期热成因气，随着埋深加大，地层环境和产甲烷古菌类型发生变化，生物甲烷生成途径发生转变。其中吉尔嘎郎图凹陷早期以乙酸发酵产气为主，晚期转变为CO2还原产气为主，并混有少量低熟热成因气；巴彦花和霍林河凹陷微生物产气途径均以乙酸发酵为主，其中霍林河凹陷还混有少量甲基发酵型生物气。研究区具有适合生物气生成的低地温、低矿化度和低热演化程度的“三低”煤层条件，其中，吉尔嘎郎图凹陷属于地堑式浅部厚煤层生物气成藏模式，巴彦花和霍林河凹陷属于半地堑式中深部承压区水力封堵生物气成藏模式。寻找适合生物成因气形成和富集的有利目标区，应是二连盆地煤层气未来勘探开发的重点方向，也是二连盆地低阶煤煤层气增储上产的现实保障。Abstract: Inner Mongolia is rich in low rank coalbed methane (CBM) resources, and research on the genetic and accumulation mechanism of coalbed methane is crucial for the selection and evaluation of low rank coalbed methane resources. Taking the low rank CBM in the key gas rich depressions of the Erlian Basin as the research objective, the geochemical characteristics of CBM and coal seam water is analyzed and the genesis and accumulation mechanism of low rank CBM is revealed by using various experimental methods, including tests on composition and carbon/hydrogen isotopes of CBM water quality, hydrogen/oxygen isotopes, and radioactive isotopes 3H and 14C of coal seam water. The result shows that the CBM component in the Erlian Basin is dominated by CH4, which belongs to dry gas. The CH4 volume fraction increases with the increase of burial depth, while the CO2 volume fraction first increases and then decreases with the increase of burial depth, and it shows high values between 300 and 500 m. The carbon and hydrogen isotopes of CH4 in the research area are generally lighter, with and δ13C(CH4) ranges from -70.3‰ to -48.0‰ and δD(CH4) ranges from -285.5‰ to -189.0‰, and δ13C(CO2) varies between -37.6‰ and 1.94‰. The chemical types of coal seam water are mainly HCO3-Na type and Cl·HCO3-Na type, and the present water environment of coal seam is relatively stable, with weak hydrodynamic forces. The apparent age of coal seam water is about 1 020-47 490 years, mainly sourced from Quaternary atmospheric precipitation, and there is no or less current surface water supply. The CBM in the Erlian Basin is mainly primary biogenic gas, mixed with a small amount of early thermogenic gas. As the burial depth increases, the geological environment and types of methanogenic archaea change, and the production pathway of biogenic methane also changes. In the Jirgalangtu depression, the biogenic methane is mainly produced by acetic acid fermentation pathway in the early stage, and is converted to CO2 reduction pathway in the late stage, mixed with a small amount of low mature thermogenic gas. In both Bayanhua and Huolinhe depressions, acetic acid fermentation is the main pathway of biogenic gas production, and there is also a small amount of methyl fermentation biogenic gas in Huolinhe depression. The research area has the "three low" coal seam conditions suitable for biogenetic gas generation, including low geothermal temperature, low salinity, and low thermal evolution. The Jirgalangtu depression belongs to the graben type biogenetic gas accumulation model in shallow thick coal seam, while the Bayanhua and Huolinhe depressions belong to the semi-graben type biogenetic gas accumulation model in middle-deep confined areas with hydraulic sealing effect. Finding favorable target areas for the formation and enrichment of biogenic gas should be a key direction for the future exploration and development of CBM in the Erlian Basin, and it is also a practical guarantee for increasing the storage and production of low rank CBM in the Erlian Basin.
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Keywords:
- Erlian Basin /
- coalbed methane genesis /
- low rank coal /
- biogenic gas /
- coal seam water /
- accumulation mechanism
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[1] 琚宜文,李清光,颜志丰,等. 煤层气成因类型及其地球化学研究进展[J]. 煤炭学报,2014,39(5):806-815. JU Yiwen,LI Qingguang,YAN Zhifeng,et al. Origin types of CBM and their geochemical research progress[J]. Journal of China Coal Society,2014,39(5):806-815.
[2] SONG Yan,LIU Shaobo,ZHANG Qun,et al. Coalbed methane genesis,occurrence and accumulation in China[J]. Petroleum Science,2012,9(3):269-280.
[3] GLASBY G P. Abiogenic origin of hydrocarbons:An historical Overview[J]. Resource Geology,2010,56(1):83-96.
[4] LOLLAR B S,LACRAMPE-COULOUME G,VOGLESONGER K,et al. Isotopic signatures of CH4 and higher hydrocarbon gases from Precambrian Shield sites:A model for abiogenic polymerization of hydrocarbons[J]. Geochimica et Cosmochimica Acta,2008,72(19):4778-4795.
[5] SCOTT A R,KAISER W R,AYERS W B. Thermogenic and secondary biogenic gases,San Juan Basin,Colorado and New Mexico:Implications for coalbed gas producibility[J]. AAPG Bulletin,1994,78(8):1186-1209.
[6] 张小军,陶明信,马锦龙,等. 含次生生物成因煤层气的碳同位素组成特征——以淮南煤田为例[J]. 石油实验地质,2009,31(6):622-626. ZHANG Xiaojun,TAO Mingxin,MA Jinlong,et al. Characteristics of carbon isotope composition from secondary biogenic gas in coalbed gases:Taking the Huainan coal field as an example[J]. Petroleum Geology & Experiment,2009,31(6):622-626.
[7] RICE D D. Composition and origins of coalbed gas[J]. Hydrocarbon from Coal Aapg Studies in Geology,1993,38:159-184.
[8] 宋岩,徐永昌. 天然气成因类型及其鉴别[J]. 石油勘探与开发,2005,32(4):24-29. SONG Yan,XU Yongchang. Origin and identification of natural gases[J]. Petroleum Exploration & Development,2005,32(4):24-29.
[9] 李清光,琚宜文,谭锋奇,等. 生物成因煤层气生成途径与判别标志及产气实验进展[C]//中国地球科学联合学术年会. 中国科学院计算地球动力学重点实验室,中国科学院大学地球科学学院:2014. [10] 陶明信. 煤层气地球化学研究现状与发展趋势[J]. 自然科学进展,2005,15(6):648-652. TAO Mingxin. Research status and development trend of coalbed methane geochemistry[J]. Advances in Natural Science,2005,15(6):648-652.
[11] 陶明信. 煤层气的成因和类型及其资源贡献[M]. 北京:科学出版社,2014. [12] 马行陟,宋岩,柳少波,等. 煤储层中水的成因、年龄及演化:卤素离子、稳定同位素和129I的证据[J]. 中国科学:地球科学,2013,43:1699-1707. MA Xingzhi,SONG Yan,LIU Shaobo,et al. Origin and evolution of waters in the Hancheng coal seams,the Ordos Basin,as revealed from water chemistry and isotope (H,O,129I) analyses[J]. Science China:Earth Sciences,2013,56:1962-1970. [13] 王海超. 沁水盆地中南部煤系气储层物性及叠置成藏模式[D]. 徐州:中国矿业大学,2017. WANG Haichao. Reservoir physical properties and superimposed accumulation model of coal measure gas in central-south Qinshui Basin[D]. Xuzhou:China University of Mining and Technology,2017. [14] WHITICAR M J. Carbon and hydrogen isotope systematics of bacterial formation and oxidation of methane[J]. Chemical Geology,1999,161(1):291-314.
[15] WHITICAR M J,FABER E,SCHOELL M. Biogenic methane formation in marine and freshwater environments:CO2 reduction vs. acetate fermentation-isotope evidence[J]. Geochimica Cosmochimica Acta,1986,50(5):693-709.
[16] 唐淑玲,汤达祯,孙斌,等. 富(含)CO2煤层气多源多阶成因研究进展及勘探开发启示[J]. 煤田地质与勘探,2022,50(3):58-68. TANG Shuling,TANG Dazhen,SUN Bin,et al. Research progress of multi-source and multi-stage genesis of CO2-enriched CBM and the enlightenments for its exploration and development[J]. Coal Geology & Exploration,2022,50(3):58-68.
[17] TANG Shuling,TANG Dazhen,TAO Shu,et al. CO2-enriched CBM accumulation mechanism for low-rank coal in the southern Junggar Basin,China[J]. International Journal of Coal Geology,2022,253:103955.
[18] MILKOV A V. Worldwide distribution and significance of secondary microbial methane formed during petroleum biodegradation in conventional reservoirs[J]. Organic Geochemistry,2011,42(2):184-207.
[19] FLORES R M,RICE C A,STRICKER G D,et al. Methanogenic pathways of coal-bed gas in the Powder River Basin,United States:The geologic factor[J]. International Journal of Coal Geology,2008,76(1):52-75.
[20] 卫三元,秦明宽,李月湘,等. 二连盆地晚中生代以来构造沉积演化与铀成矿作用[J]. 铀矿地质,2006,22(2):76-82. WEI Sanyuan,QIN Mingkuan,LI Yuexiang,et al. Tectono-sedimentary evolution of Erlian Basin since Late Mesozoic and sandstone-hosted uranium metallogenesis[J]. Uranium Geology,2006,22(2):76-82.
[21] 陶俊杰,申建,王金月,等. 二连盆地吉尔嘎朗图凹陷煤层气成因类型及勘探方向[J]. 高校地质学报,2019,25(2):295-301. TAO Junjie,SHEN Jian,WANG Jinyue,et al. Genetic Types and exploration prospect of coalbed methane in Jiergalangtu Depression,Erlian Basin[J]. Geological Journal of China Universities,2019,25(2):295-301.
[22] 孟芹,李玲,李杰,等. 二连盆地巴彦花凹陷煤层气成因类型及生气潜力[J]. 煤田地质与勘探,2023,51(11):24-33. MENG Qin,LI Ling,LI Jie,et al. Genetic type and gas-generating potential of coalbed methane in the Bayanhua Sag,Erlian Basin[J]. Coal Geology & Exploration,2023,51(11):24-33.
[23] FABER E,STAHL W. Geochemical surface exploration for hydrocarbons in North Sea[J]. AAPG Bulletin,1984,68(3):363-386.
[24] KVENVOLDEN K A. A review of the geochemistry of methane in natural gas hydrate[J]. Organic Geochemistry,1995,23(11):997-1008.
[25] 韩永,王广才,邢立亭,等. 地下水放射性同位素测年方法研究进展[J]. 煤田地质与勘探,2009,37(5):37-42. HAN Yong,WANG Guangcai,XING Liting,et al. Advances in studying groundwater radioisotope dating methods[J].Coal Geology & Exploration,2009,37(5):37-42.
[26] 宋佩德,范莉,潘结南,等. 新郑矿区地下水类型及水源判别[J]. 煤矿安全,2014,45(2):165-168. SONG Peide,FAN Li,PAN Jienan,et al. Groundwater types and water source discriminantion for Xinzheng mining area[J]. Safety in Coal Mines,2014,45(2):165-168.
[27] 李跃国,姚程鹏,杨曙光,等. 准南米泉地区煤层气成因及其富集成藏机理研究[J]. 煤炭科学技术,2021,49(4),220-226. LI Yueguo,YAO Cengpeng,YANG Shuguang,et al. Study on origin and accumulation mechanism of coalbed methane in Miquan Area of southern margin of Zhunggar Basin[J]. Coal Science & Technology,2021,49(4),220-226.
[28] 杨兆彪,秦勇,秦宗浩,等. 煤层气井产出水溶解无机碳特征及其地质意义[J]. 石油勘探与开发,2020,47(5):1000-1008. YANG Zhaobiao,QIN Yong,QIN Zonghao,et al. Characteristics of dissolved inorganic carbon in produced water from coalbed methane wells and its geological significance[J]. Petroleum Exploration & Development,2020,47(5):1000-1008.
[29] BAUBLYS K A,HAMILTON S K,GOLDING S D,et al. Microbial controls on the origin and evolution of coal seam gases and production waters of the Walloon Subgroup;Surat Basin,Australia[J]. International Journal of Coal Geology,2015,147-148:85-104.
[30] GOLDING S D,BOREHAM C J,ESTERLE J S. Stable isotope geochemistry of coal bed and shale gas and related production waters:A review[J]. International Journal of Coal geology,2013,120:24-40.
[31] 戴金星,宋岩,戴春森,等. 中国东部无机成因气及其气藏形成条件[M]. 北京:科学出版社,1995. [32] 汤达祯. 煤变质演化与煤成气生成条件[M]. 北京:地质出版社,1998. [33] 来守超. 煤层生物甲烷产生和氧化过程及其微生物学特征研究[D]. 北京:中国农业科学院,2019. LAI Shouchao. Pathways and Microbiological Characterization of Coalbed Biomethane Production and Oxidation[D]. Beijing:Chinese Academy of Agricultural Sciences,2019.
[34] 李站伟,汤达祯,唐淑玲,等. 准噶尔盆地南缘富CO2低阶煤层气藏的形成机理研究[J]. 煤炭科学技术,2021,49(3):175-180. LI Zhanwei,TANG Dazhen,TANG Shuling,et al. Study on formation mechanism of CO2-enriched CBM reservoirs in low-rank coal seams from southern Junggar Basin[J]. Coal Science and Technology,2021,49(3),175-180.
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