准噶尔盆地马桥凸起异常高压成因及油气成藏模式

准噶尔盆地马桥凸起下侏罗统三工河组上部流体压力封闭层呈等深（顶部深度为４．４７０～４．４８５ｋｍ）分布，其以上为正常流体压力系统，以下为异常高压流体系统（压力系数可达１．９～２．１）。压力封闭层的形成除与储集层物性因素有关之外，还与地层水运移过程中的矿化热液沉淀作用有关。晚白垩世以来，封闭层与其下伏的三工河组中、下部及八道湾组共同阻挡了深部地层水及油气进一步向上运移，成为马桥凸起区的区域性盖层，使二叠系烃源岩早期（晚三叠世末至侏罗纪）生成的石油与晚期（白垩纪以来）生成的油气相分隔，并阻止下侏罗统煤系烃源岩生成的天然气向中侏罗统运移。据此认为，在马桥凸起区，中侏罗统发现的石油是深部油气藏早期部分破坏而形成的次生油藏；下侏罗统异常高压油气藏为多源油气多期混合成藏，因储集层物性差，大规模成藏的可能性较小；深部石炭系、二叠系和三叠系的圈闭有良好的成藏条件，应有较好的油气勘探前景。图４参３（梁大新摘）

Over pressure origin and hydrocarbon pool forming mode of Maqiao uplift in Junggar basin.

The pressure sealing zone of fluid in upper part of Lower Jurassic Sangonghe Formation in Maqiao uplift of Junggar basin exhibits an isobathic distribution with the top depth being from 4.470 to 4.485km, above the depth, is the normal fluid pressure system, and below the depth is the over pressure fluid system (the pressure coefficient can be up to 1.9 2.1). The formation of pressure sealing zone is related not only to reservoir properties, but also to the precipitation of minerals from thermal liquid during migration of formation water. Since Late Cretaceous this sealing zone together with its underlying middle lower part of Sangonghe Formation and Badaowan Formation have prevented the deep formation water and hydrocarbon from further upward migration, and became the regional cap rocks of Maqiao uplift, isolating the early generated oil from Permian hydrocarbon source rocks and late (since Cretaceous) generated oil, and preventing the natural gas derived from Lower Jurassic coal measures from migrating to the Middle Jurassic. Based on this,it is thought that the oil pools discovered in Middle Jurassic should be the secondary pools derived from the deep oil and gas pools by early partly destruction; the Lower Jurassic abnormal pressure oil and gas pools are mostly combination ones under multiple sources and multiple generation, which have poor reservoir properties and not easily form big oil and gas pools; the deep Carboniferous, Permian and Triassic traps have favourable pool forming conditions and should have good oil and gas exploration potentials.