巨厚低阶煤煤层气储层关键成藏地质要素及评价方法——以二连盆地巴彦花凹陷为例

为了建立巨厚低阶煤煤层气资源评价方法，以二连盆地巴彦花凹陷为研究对象，通过研究煤层气成因、煤层埋深、煤层厚度、煤储层物性、含气性、水文地质和盖层等，总结了巨厚低阶煤煤储层的关键成藏地质要素，并进一步建立了新的低阶煤煤层气资源潜力评价方法，圈定了巴彦花凹陷煤层气勘探开发有利区和目标区。结果表明:巴彦花凹陷主要含煤地层为下白垩统腾格尔组（K₁t），以褐煤和长焰煤为主，显微组分以镜质组为主，煤层气的形成是生物成因为主、混合成因为辅的成烃模式，生物成因气占主导地位；研究区共发育3个煤组，煤储层厚度大，发育面积广，埋深适中，保存条件好，含气量较高，空气干燥基含气量最高可达4.45 m3/t，1、2煤组有利于形成煤层气藏，3煤组有利于形成煤系砂岩气藏。根据建立的资源潜力评价方法，煤层气勘探开发的最优目标区位于巴彦花凹陷北部。 

Key geological factors and evaluation methods for huge low-rank coalbed methane reservoirs:Taking Bayanhua depression in Erlian basin as an example

In order to evaluate the potential of low rank CBM resources with large thickness,Bayanhua depression in Erlian basin is studied.By studying the genesis of CBM,buried depth of coal seam,thickness of coal seam,physical properties of coal reservoir,gas content,hydrogeology and cap rock,the key geological elements of thick and low coal rank coal reservoirs are summarized.Furthermore,a new low rank CBM resource potential evaluation method is established,and the favorable and target zones for CBM exploration and development in Bayanhua depression are delineated.The results show that the main coal-bearing strata in Bayanhua depression is the Lower Cretaceous Tenggeer Formation(K1t),which is dominated by lignite and long-flame coal,and the maceral is mainly vitrinite.CBM is mainly biogenetic and mixed genetic CBM is auxiliary.A total of three coal groups are developed in the study area.The coal reservoir has large thickness,wide development area,moderate buried depth,good preservation conditions,high gas content,and gas content of air drying base is up to 4.45 m^3/t.No.1 and No.2 coal groups are conducive to the formation of CBM reservoirs,and No.3 coal group is conducive to the formation of coal-bearing sandstone gas reservoirs.According to the established resource potential evaluation method,the optimal target area for CBM exploration and development is located in the northern part of Bayanhua depression.