西藏措勤盆地油气成藏条件分析

CONDITIONS FOR THE FORMATION OF OIL AND GAS POOL IN CUOQIN BASIN

根据野外地质调查资料,对措勤盆地的油气生成、储集、运移、圈闭等条件进行了分析;认为盆地中发育的主要烃源岩有7套,岩石类型主要为灰岩,储集层主要为各种灰岩和砂岩;有利的生储盖组合型式主要为自生自储自盖式及互层式生储盖组合;野外调查发现的油气苗及微观包裹体的研究均证实了盆地内油气运移过程的发生;推测盆地内主要的圈闭及油气藏类型为背斜及断层遮挡油气藏,K2 R构造层主要发育完整的背斜油气藏,J K1构造层主要发育被断层复杂化的背斜油气藏;建议将主要目的层放在较新的构造层中。

On the basis of the field geologic examination data, the paper systematically studies the conditions of the generation and migration and trap of oil and gas in Cuoqin basin. There are seven sets hydrocarbon source rock in Cuoqin basin. The rock types of the source rock is mostly limestone. These source rocks are in Jiega formation, Langshan formation, Duoba members of Duoni formation, Xiala formation, Dewukaxia formation, Keerduo formation. The source rock of mud rock is mostly shale. It is in Chuanba members of Duoni formation. The result of organic geochemistry analysis has revealed that the source rocks in the Langshan formation, Xiala formation, Dewukaxia formation is better than others in Cuoqin basin.The reservoirs are mostly limestone and sandstone in Cuoqin basin. These limestone reservoirs are mostly in Langshan formation, Duoba members of Duoni formation, Xiala formation, Zhalongema formation, Dewukaxia formation, Keerduo formation. The sandstone reservoirs are mostly in Niubao formation, Chuanba members of Duoni formation, Zelong group, Daxiong group, Jienu group, Angjie formation. The reservoirs in Cuoqin basin are mostly inferior reservoir.The seals in Cuoqin basin are high quality seal. The best combinations of source rock and reservoir and seal in Cuoqin basin are that the source rock and reservoir and seal are same layer and that the source rock and reservoir is alternate layer. Petroleum migration has been confirmed by the surface indication and the microcosmic enclosure in Cuoqin basin. In Cuoqin basin, the main types of trap and petroleum pool are anticline trap and fault clock trap. The formation model of petroleum pool is different from each other in every synthem. In K2R synthem, anticline is the main type of petroleum pool. In JK1 synthem, the main type of petroleum pool is the anticline that has been modified by fault.Due to many times of tectonization that Cuoqin basin has been experienced, it is very disadvantage to the save of petroleum pool. The main aim stratum must be the later synthem.