珲春盆地低煤阶煤层气富集规律

Low rank enrichment of coalbed methane in Hunchun basin

珲春盆地煤层气取得工业突破对我国低煤阶含煤盆地的煤层气勘探具有重要意义。通过对珲春盆地低煤阶煤层气成藏条件的深入剖析,探讨了低煤阶煤层气富集的主控因素及其成藏模式。结果表明,珲春盆地具有煤阶低、煤层多、煤层薄的特点,构造作用、沉积特征和岩浆岩侵入是其富集成藏的主控因素。盆地西部的褶皱和断层伴生带不仅为生物气创造有利环境,而且为煤层气二次成藏提供场所,形成"连续褶皱"富气模式;沼泽和天然堤微相的垂向叠置,使得作为煤层直接顶底板的泥岩和致密砂岩对煤层气起到更好的封闭作用;局部辉绿岩侵入体促使煤层再次生气,同时大大改善了煤岩的物性。因此,珲春盆地西部是煤层气高产富集区,具有巨大勘探开发潜力。

To obtain the industrial breakthrough of coalbed methane in Hunchun basin hasgreat significance for the exploration of coalbed methane(CBM) in China’s low rank coal basins. Through the deepened analysis on the res-ervoir-forming conditions of coalbed methane of low rank coal in Hunchun basin, the paper discussed the major controlling factors of CBM enrichment of low rank coal and its reservoir-forming model. The results show that Hunchun basin is characterized by low coal rank, multiple and thin seams. There are three main control factors for CBM accumulation, including tectonic setting, sedimentary characteristics and magmatic rock intrusion. The area with faults and folds in the west of the basin has not only created the favorable environments for biogas, but also provided the place for secondary reservoir forming, eventually forming the gas enrichment model of "continuous fold". The vertical superimposition of microfacies of marshes and natural levee which made mudstone and dense sandstone as the direct roof and floor of coal seams have better sealing effect for CBM, local diabase intrusion inside coal seams made again hydrocarbon to be generated, and greatly improved the physical properties of coal. Therefore, the west of Hunchun basin is an area rich in CBM and has a great potential for exploration and development.