准噶尔盆地深、浅层煤层气富集模式对比分析

Comparative analysis on the enrichment patterns of deep and shallow CBM in Junggar Basin

  • 摘要: 准噶尔盆地煤层气资源丰富,煤层气勘探获得了一定突破,但整体勘探程度低,深、浅层煤层气富集规律差异性大,为了探索深、浅层煤层气赋存的差异,合理地开发地下资源,通过对深、浅层煤层气的气源特征、地质条件、保存条件等方面的研究,分析了深、浅层煤层气赋存特征及成藏主控因素,建立了深、浅层煤层气成藏模式,提出了煤层气勘探方向。结果表明,浅层煤层气具有“生物气+热成因气+深部运移气”三气源补给特征,煤储层以大孔和过渡孔为主,煤层中除了吸附气外,还有大量的游离气,游离气平均占到了36%,在褶皱构造的向斜部位和水动力滞留区富集成藏; 深层煤层气具有“热成因气+深部运移气”两气源补给特征,西山窑组以游离气为主,占60%以上,在构造高部位聚集成藏,八道湾组煤层和砂体叠置发育,都是天然气的有效储层,形成了吸附、游离共生气藏。初步认为在浅层开展煤层吸附气勘探为主兼探游离气,深层西山窑组主要勘探煤层游离气,寻找岩性圈闭或构造圈闭,深层八道湾组开展“煤层气+砂岩气”共探共采,提高煤系资源利用率。

     

    Abstract: Coalbed methane (CBM) resources are abundant in Junggar Basin and some breakthroughs have been made in CBM exploration.However, the overall exploration level is low, besides there are great differences in the enrichment laws of deep CBM and shallow CBM.In order to find out the differences and more rational use of resources, this paper studied the source characteristics, geological conditions and preservation conditions of deep CBM and shallow CBM, analyzed the occurrence characteristics and main controlling factors of deep CBM and shallow CBM, and established the reservoir-forming model of deep CBM and shallow CBM, at last, pointed out the exploration direction.The results show that the shallow CBM has the characteristics of three gas sources replenishment, the gas sources are biogas, thermogenic gas and deep migration gas.Coal pore is dominated by macro pore and transitional pore.In addition to adsorbed gas, there is a large amount of free gas in coal seam, which accounts for 36% on average.Shallow CBM are accumulated in syncline of fold structure and hydrodynamic retention area.Deep CBM has the characteristics of two gas sources replenishment.The two gases are the mogenic gas and deep migration gas.The Xishanyao Formation is dominated by free gas, accounting for more than 60% of the total, accumulated in the high part of the structure.Coal and sand of the Badaowan Formation are well developed, which are effective reservoir of natural gas, also, forming an adsorption-free symbiotic gas reservoir.It is preliminarily considered that the exploration of adsorbed gas is the first, then explored the free gas in shallow strata.While in deep strata, the exploration of free gas in the Xishanyao Formation is mainly to search for lithologic traps or structural traps.The CBM and sandstone gas are explored together in the Badaowan Formation in order to improve the utilization rate of resources.

     

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