新疆低煤级储层煤层气成藏模式研究

With low rank coal reservoir in Junggar basin and Tuha basin of Xinjiang as the research object, focused on coalbed methane(CBM) accumulation model of low rank coal reservoir, based on physical simulation of biogenic and thermogenic hydrocarbon generation, physical and numerical simulation of Hydro-geological evolution and numerical simulation of coal reservoir pressure evolution, dynamic balance relationship between geological process and formation, migration and accumulation of CBM will be discussed by evolutionary analysis of reservoir forming condition of "five histories(History of sedimentary evolution, tectonic evolution, thermal evolution, hydrocarbon generation of organic matter, and groundwater activities)" and "three fields(Construct dynamic field, thermal power plants and water dynamic field)". And then in the different stages of hydrocarbon generation, interaction way and mechanism of tectonic dynamics, thermodynamics and hydrodynamics will be put forward, as well as CBM accumulation model of low rank coal reservoir be established. The results can help to explore an effective way to perfect and develop the basic theory of CBM in China, and to reduce risk in the CBM exploitation of low rank coal reservoir. There exists a broad perspective on CBM development of the most low rank coal basins in China.

以新疆准噶尔盆地、吐哈盆地低煤级储层为研究对象，围绕低煤级储层成藏模式这一根本目的，通过煤盆地"五史"与"三场"成藏条件演化分析，基于生物、热产烃物理模拟、水文地质演化的物理模拟与数值模拟、储层压力演化的数值模拟研究，探讨地质作用过程与煤层气形成、运移、成藏的动平衡关系；揭示不同生烃阶段，构造动力、热动力、水动力相互作用方式及机制；建立低煤级储层煤层气成藏模式。为完善和发展我国煤层气基础理论，减少低煤级储层煤层气开发风险探索出一条行之有效的途径。在我国众多低煤级盆地煤层气开发中具有广泛的应用前景。

煤层气成藏是由构造动力、热动力、水动力等多个动力场协同作用的动态演变过程，前人提出的低煤级储层煤层气成藏模式多是基于单方面因素。本次通过物理模拟低煤级煤次生生物气/热成因气的产出过程、阶段产气量、产气率、产出气组分及其碳氢同位素，数值模拟低煤级储层埋藏史、热演化史、流体压力演化史和吸附态、溶解态、游离态含气量的演变过程，结合研究区地质条件，考虑埋深、水文地质条件、煤层气成因、相态含气量、成藏方式等成藏要素，综合构建了低煤级储层煤层气成藏模式。. 估算新疆地区2000 m以浅褐煤储层煤层气资源量为3098亿m3，长焰煤储层煤层气资源量为3.6万亿m3；次生生物产气过程中检测出了C29~C32—ββ生物藿烷系列以及C24四环二萜烷等生物标志化合物，判定产出气是通过乙酸发酵方式形成的生物气；低煤级煤生烃增压对储层压力的贡献微弱，流体压力（水压）及水动力条件控制了煤层含气量的分布；准噶尔盆地存在浅部-弱径流-生物成因-吸附气-自生自储煤层气成藏模式、中部+深部-弱径流-热成因-吸附气-内源运移煤层气成藏模式、深部-滞留-热成因-吸附气+游离气-外源运移煤层气成藏模式、超深部-滞留-热成因-游离气+吸附气-外源运移煤层气成藏模式。