煤层气-煤型气叠合型气藏成藏机理与地质预测方法研究

Having a case study of coalbed methane-coal derived gas superposed reservoirs of Shanxi formation in Jiyang depression,Bohaiwan basin,applying key methods and techniques of coal sorption, diffusion and seepage experiments, comprehensive dermination of pool-forming geological factors and relative information extraction, numerical modelling of pool-forming processes,restoring history of tectonic, burial and geothermal evolution,and paleogeographical restoration by means of facies ratio within short periods,the applicants dissect typical reservoirs, select study on deep coal reservoir features and pool-forming geological conditions of coalbed methane-coal derived gas superposed reservoirs as breach, and consider study on favorable assemblage of pool-forming geological factors and dynamic geological processes of coalbed methane-coal derived gas reservoirs as core tasks. They attempt to explore geological controlling regulation of coalbed methane-coal derived gas superposed reservoirs, to establish pool-forming geological model and geological prediction methodology of coalbed methane-coal derived gas. And they expect to reveal scientific intention of the intergrated gas-bearing system anf the coalbed methane-coal derived gas reservoir in coal-bearing strata of coal and petroleum bearing basins, and to lay significant theoritical foundation for geological prospect of coalbed methane-coal derived natural gas. The research is aiming at providing a new thought to break bottleneck puzzles encountered during exploration and development in coal bearing sequences such as coal derived gas resource scale being little and deep coalbed methane recovery being diffficult in coal and petroleum bearing basins, and hopefully develop a new direction for deep coal bearing stata pertroleum prospecting in coal and petroleum bearing basins represented by Bohaiwan basin.

以渤海湾盆地济阳坳陷山西组煤层气-煤型气叠合型气藏为研究实例，拟采用模拟深部地层条件煤储层吸附解吸与扩散渗流实验、成藏地质要素录井-测井-地震综合识别与信息提取、成藏过程数值模拟技术、构造-埋藏-热演化史重建、短时限相比法古地理恢复等关键方法技术，通过典型气藏解剖，以深部煤储层特征和叠合型气藏成藏地质条件研究为突破口，以叠合气藏成藏地质要素有利组合配置和成藏动力学地质过程研究为核心内容，探寻煤层气-煤型气叠合型气藏分布赋存地质控制规律，建立煤层气-煤型气叠合型气藏成藏地质模式与地质预测理论方法；以期揭示含煤、油气盆地煤系地层统一含气系统和煤层气-煤型气叠合型气藏的科学内涵，奠定煤层气-煤型气叠合型气藏地质勘探重要理论基础；为破解含煤油气盆地煤型气资源规模小、深部煤层气开发技术难度大的煤系油气勘探开发瓶颈问题提供新思路，有望开拓以渤海湾盆地为代表的含煤油气盆地深部含煤地层油气勘探的新方向。

以渤海湾盆地济阳坳陷山西组和贵州盘县地区龙潭组为研究实例，采用深部煤储层模拟实验，成藏地质信息综合识别与提取，成藏过程数值模拟，煤层构造-埋藏-热演化史恢复，高精度古地理恢复等五项关键技术，深入研究了煤系叠合型气藏成藏地质背景与条件、成藏地质要素与成藏特征、成藏动力学地质过程、地质控制与成藏模式、地质预测方法和地质适配性勘探开发技术等。研究结果表明：煤系叠合型气藏为煤系特有的统一含气系统和非常规气藏类型，河道砂体与煤层接触型、煤层-砂岩-泥岩互层型两类煤系叠合型气藏分别发育于华北C-P稳定克拉通和陆表海背景下的浅水三角洲沉积体系和华南P古陆周缘的海岸带与三角洲沉积体系，并经历多期次煤层埋藏热演化和生烃史；煤系存在煤层气藏、煤型气藏和煤层气-煤型气叠合型气藏三类原生气藏类型，其形成和发育具有紧密的成因联系；济阳坳陷煤层吸附能力转折临界埋深为800m，深部煤储层温压体系转折临界深度为1800m，在临界深度煤层含气量和煤层气赋存状态都发生显著变化；应用深部煤层吸附量预测模型可以较好地恢复济阳坳陷深部煤层气体吸附量演化历史，有机质生烃史和生气关键事件对煤层吸附气体、含气量和排烃有显著影响；叠合型气藏成藏动力学C-S-SGR模型是煤层吸附排烃与砂体充注过程、物质平衡及能量平衡关系的量化表征，数值模拟方法可有效揭示煤系叠合型气藏成藏动力学过程和机理；沉积体系和岩相古地理演化是煤系叠合型气藏主控因素，煤系叠合型气藏发育地层-岩性气藏的成因特征；应用叠合型气藏成藏模式和基于高精度岩相古地理分析技术的预测方法，预测得到了济阳坳陷煤系叠合型气藏发育的5个有利区；“层段优选、小层射孔、分段压裂、投球分压、合层排采”是贵州盘县龙潭组煤系叠合型气藏有效开发的地质适配性工艺技术。煤系叠合型气藏的研究对华北渤海湾盆地C-P煤系深部煤层气开发和华南贵州龙潭组煤系气兼探共采有特别重要的科学和实践意义。