中国低煤阶煤层气多元成藏特征及勘探方向

我国低煤阶含煤盆地地质背景复杂,煤层气富集成藏具有自身的特殊性,煤层气勘探一直处于小型试验阶段。为了促进我国低煤阶煤层气的勘探开发,在系统分析、总结我国含煤盆地类型、煤层气成因、赋存状态、富集模式的基础上,梳理了目前勘探开发工作面临的挑战与科研攻关目标,并提出低煤阶煤层气的有利勘探方向。结果表明:(1)我国低煤阶煤层气具有盆地类型多元、煤层气成因类型多元、赋存状态多元、富集类型多元的成藏特征;(2)低煤阶煤层气勘探面临目标区优选、深层煤系气共探共采系统评价、钻完井及增产改造工艺等3个方面的挑战;(3)应加强对煤层气成藏过程及动力学机制、气源成因及其资源贡献、吸附态和游离态煤层气空间分布规律及地质控制因素等的研究攻关,开展煤层气资源有效性和可采性评价,形成一套深部煤系气勘探开发评价方法。结论认为:(1)我国浅层煤层气资源有利勘探区包括二连盆地吉尔嘎朗图、霍林河、白彦花等凹陷,海拉尔盆地伊敏、呼和湖、陈旗等凹陷,鄂尔多斯盆地彬县、焦坪、黄陵、乌审旗东部等地区,以及准噶尔盆地南缘地区;(2)深层煤层气资源则主要分布在准噶尔、吐哈、三塘湖、海拉尔和三江等盆地或盆地群。

Low-rank coalbed methane gas pooling in China: Characteristics and exploration orientation

Due to the complicated geological settings of low-rank coal-bearing basins and particular CBM enrichment characteristics, CBM exploration has been in a test stage. In view of this, we first summarized coal-bearing basin types, CBM gas origins, occurrence states and accumulation modes, etc. On this basis, we analyzed the present challenges and further goals of scientific research and put forward the favorable exploration orientation for CBM gas reservoirs of low rank coals. The following findings were obtained. (1) The low-rank coalbed methane gas pooling is characterized by diversified basin types, various origins, multiple occurrence states, and accumulation modes. (2) The low-rank coalbed methane gas exploration is now challenged by optimal selection of exploration targets, evaluation of co-exploration and co-production system of deep-strata coal-derived gas, and reservoir stimulation technologies together with drilling & completion. (3) Further related research will focus on the CBM gas pooling process and dynamic mechanisms, gas origins and resource contribution, adsorptive and free CBM gas space distribution laws and geological controlling factors, and CBM gas resource availability and recoverability assessment should be made, thus a series of deep-strata coal-derived gas exploration and development evaluation methodologies will be developed. In conclusion, it is considered that favorable CBM gas exploration zones in shallow strata will include Jiergalangtu, Huolinhe, Baiyanhua depressions in the Erlian Basin Groups, Yimin, Huhehu, Chenqi depression in the Hailar Basin Groups, and Binxian, Jiaoping, Huangling, eastern Wushenqi in the Ordos Basin, and the southern margin areas in the Junggar Basin, while those zones in deep strata will include the areas in the Junggar, Tuha, Santanghu, Hailar and Sanjiang basins or basin groups.