我国中西部前陆盆地天然气分布规律与有利勘探区带优选

我国中西部前陆盆地天然气资源丰富，5个主要富气盆地的资源探明率只有9.3%，天然气勘探潜力较大。中西部前陆盆地大中型气田有7种富集成藏模式，其中冲断挤压作用是天然气分布的重要控制因素。研究分析了前陆盆地各二级构造带大中型气田类型及分布特点，认为冲断带下盘大型构造圈闭群、前渊斜坡岩性尖灭区带与浅层次生气藏、前缘隆起上的断块圈闭群等是前陆盆地有利的天然气富集区带。依据对前陆盆地地质规律深入研究的结果，结合目前天然气勘探实际，提出了大中型气田富集区带的优选原则，并优选了中西部前陆盆地5个天然气富集区带塔里木盆地库车前陆冲断带中的克依构造带逆冲断裂下盘的膏盐层下部大型构造圈闭群，柴达木盆地北缘冲断带的冷湖—南八仙构造带，四川盆地川西北前陆凹陷前渊区带的盐井沟—苏马头—龙泉山侏罗系浅层气，川西前缘斜坡带的梓潼斜坡上三叠统须家河组岩性尖灭区带，准噶尔盆地南缘第二排、第三排构造带的第三系、白垩系气藏。图1参4（曾宪斌摘）

The distribution rule of natural gas and the screening of profitable exploration areas in foreland basins of Central and West China

The natural gas resource is rich in Central and West China. The ratio of proved reserves is only 9.3% in the five gas rich basins there the natural gas exploratin potential is large. There are seven models of major gas fields in the foreland basins. Distribution of gas rich areas is mainly controlled by the fault-fold or rupture. After studying the type of development and distribution characteristics of large-medium-sized gas fields of each second-order structure in the foreland basins, the authors hold that the large-scale structural traps in the lower block of thrust belt, the lithological fringe in the foreland slope area and shallow secondary gas pools as well as the fault block traps in the frontal uplifts of foreland basins etc. Are favourable enrichment zones of natural gas in this kind of basin. On the basis of detail geologic research for the foreland basin and the present situation for natural gas exploration, the authors draw out the useful ways to select profitable exploration areas, and select five profitable gas rich areas in the foreland basins of Central and West China. They are large-scale structural traps underneath the salt bed in the lower wall of over-thrust fault in Keyi structural zone of Kuqa foreland thrust belt in Terim basin, Lenghu―Nanbaxian structural zone in the thrust belt on the northern fringe of the Qaidum basin, Jurrasic Yanjinggou-Sumatou-Longquanshan shallow gas beds of foreland sag in northwestern Sichuan basin, lithological fringe zone in Upper Triassic Xujiahe Formation on Zitong slope of Chuanxi front slope belt and Tertiary and Cretaceous gas reservoirs of second and third structures in the southern fringe of Jungar basin.