天然气基础地质理论研究新进展与勘探领域

New progress in basic natural gas geological theories and future exploration targets in China

随着天然气勘探向深层、超深层、非常规等领域拓展,勘探对象日趋复杂,需要不断完善现有的天然气基础地质理论,以指导勘探和发现更多的大气田。为此,"十二五"以来,在开展天然气基础地质理论研究的基础上,分析探讨了今后大气田勘探的重点领域。结果表明:(1)"十二五"以来完善了有机质全过程生烃理论,丰富和发展了干酪根热降解生烃、有机质接力成气等有机质生烃地质理论;(2)建立了多元天然气成因鉴别新方法、不同类型封盖层定量评价方法、低生烃强度区致密砂岩气成藏理论、古老碳酸盐岩大气田成藏理论,丰富和发展了天然气生成、天然气成因鉴别和天然气成藏等基础地质理论,有效指导了近年来我国重点盆地大气田的勘探突破和重大发现。结论认为:(1)古老碳酸盐岩、致密砂岩、前陆区、页岩、火山岩等是今后大气田勘探的主要领域;(2)克拉通和前陆盆地仍是大气田勘探的重点领域,古隆起、平缓斜坡、冲断带是大气田的主要富集区带;(3)古老层系、深层领域是未来天然气勘探的重点方向;(4)海相盆地原油裂解气、致密砂岩气和页岩气是未来天然气储量、产量增长的重要接替资源。

As natural gas exploration expands to deep, ultra-deep and unconventional areas, more and more complex exploration targets are encountered. In this circumstance, it is necessary to improve the existing basic natural gas geological theories for guiding the exploration and discovery of more giant gas fields. In this paper, the researches on basic natural gas geological theories since the beginning of the 12th Five- Year Plan were engaged, and then the key exploration target zones were analyzed. Some results were obtained. First, the theory of whole-pro- cess hydrocarbon generation of organic matter has been improved and the geologic theories of organic matter hydrocarbon generation （e.g. the thermal evolution model of kerogen degradation and hydrocarbon generation and the successive gas generation of organic matter） have been developed. Second, multi-element natural gas genesis identification method, quantitative evaluation method for different types of seals/ caprocks, tight sandstone gas accumulation theory for low hydrocarbon generation intensity region, and hydrocarbon accumulation theory for large-size ancient carbonate rock gas field have been established, and the geological theories of gas generation, genesis identification and hydrocarbon accumulation have been developed to provide the effective guidance for the exploration breakthrough and discovery of largesize gas fields in the key basins of China recently. Four conclusions were reached. First, ancient carbonate rocks, tight sandstone, foreland region, shale and volcanic rocks are primary exploration targets for discovering giant gas fields. Second, craton and foreland basins are still the key exploration areas, and paleo-uplift, gentle slope and thrust belt are the main enrichment zones. Third, ancient series of strata and deep formations are critical gas exploration targets in the future. Fourth, oil cracking gas in marine basins, tight sandstone gas and shale gas are the important replacement resources for future gas reserves and production growth.