中国天然气基础地质理论问题研究新进展

经过30多年的天然气科技攻关研究，已经形成了具有中国特色的天然气成气、成藏地质理论，但随着国内天然气勘探难度的增大和供需矛盾的突显，需要不断发展和完善天然气地质理论，以指导寻找和发现更多的天然气资源。为此，“十一五”期间开展了有关大气田形成基础地质理论问题的攻关研究，取得了一系列重要进展和认识，主要包括：①3种成因类型天然气（煤成气、原油裂解气和生物气）的生成下限值降低；②高温高压条件下（温度超过150 ℃、压力超过40 MPa）砂岩溶蚀速率增大2～3倍；③建立了气藏盖层的多因素综合定量评价方法，盖层评价逐步走向定量化；④研究了5类气藏（大面积低渗透砂岩、礁滩与岩溶、火山岩、超高压、生物气）的形成条件与主控因素，建立了其成藏模式、明确了其分布规律。进而深化了3大领域的天然气勘探理论：①发展了近源高效聚集的低渗透砂岩气藏勘探理论，推动了苏里格气田、川中须家河组气藏天然气储量快速增长；②创立了以生烃断槽为基本单元的火山岩气藏勘探理论，实现了松辽盆地深层中小断陷火山岩气藏勘探的系列突破；③深化了碳酸盐岩台缘礁滩气藏勘探理论，有效指导了龙岗气田主体评价勘探与向西向东扩展以及四川盆地的天然气风险勘探。

New progress in the studies on basic geological theories of natural gas in China

After more than 30years’technical research of natural gas,Chinese scholars have developed their own geological theories on natural gas accumulation and gas pooling.However,along with the increasing difficulty of natural gas exploration and obvious contradiction between supply and demand,such geological theories need to be continuously developed and completed as guidance to tap and discover more natural gas resources.In view of this,the related basic geological theories on the formation of large gas fields were studied during the national Eleventh Five-Year Plan and the achieved results are presented herein.(1) The lower limit values of the generation of three types of natural gas including coal-derived gas,oil-cracking gas,and biogas are lowered down.(2) The erosion rate of sandstones is increased twice to three times under high temperatures over 150℃and high pressures more than 40MPa.(3) The quantitative method of evaluating the quality of cap rocks by multiple factors is developed so that the assessment of cap rocks is gradually becoming quantitative.(4) The forming conditions and main controlling factors of five types of gas reservoirs,including large-area and low-permeability sandstone,bank / reef and karstification,volcanic,super-high pressure,and biogas,are studied and the gas pooling modes and distribution laws are set up and clarified.Furthermore,more understandings are obtained about the theories of natural gas exploration in the above-mentioned three major target zones.(1) The theory of highly efficient gas accumulation near source rocks is developed for the exploration of low-permeability sandstone gas reservoirs,which helps to significantly increase the reserves of gas reservoirs in the Sulige Gas Field and the Xujiahe gas reservoirs in the Middle Sichuan Basin.(2) The theory of regarding the hydrocarbon generation at fault troughs as the basic unit is advanced for the exploration of volcanic gas reservoirs,which helps to achieve great breakthrough in the gas exploration of middle and small faulted volcanic reservoirs in the deep Songliao Basin.(3) The theory is deepened about the exploration of platform edge and reef carbonate gas reservoirs,which guides the whole exploration assessment of the Longgang Gas Field and further extension of gas exploration to its west and east and the risk-taking gas exploration in the Sichuan Basin.