含油气盆地中膏盐岩层对油气成藏的重要影响

The impact of saline deposit upon the hydrocarbon accumulation in petroliferous basin

多数盆地的膏盐岩为蒸发成因,部分地区则为深部热卤水作用的产物。研究表明:膏盐岩的形成环境(主要是陆相湖盆蒸发环境)有利于有机质的保存,为油气生成提供物质保障。深部热卤水作用致使深部热流体上侵,将提高烃源岩的油气转化效率以及为无机油气藏的形成提供了条件。膏盐岩能使其下部地层保持较高的孔隙度并且形成次生孔裂隙(但也可堵塞下部地层原生孔隙),同时本身也可成为油气的运移通道或储集空间,是其下部异常高压系统得以形成的重要条件,有利于油气藏的保存。膏盐层可以单独封盖油气,也可与断层联合封堵,具有很好的封盖能力。膏盐层对其上、下地层的区域构造样式产生影响,也限定了油气运移的途径和聚集层位。

Saline-deposits in most basins are formed through evaporation and some are the products of deep thermal brine. Research shows that （ 1 ） the formation environments for saline deposits, dominated by evaporate environments in continental lake basins, are favorable for the preservation of organic matters and the generation of hydrocarbon; （2） the upward intrusion of deep thermal fluid enhances transformation ratio of hydrocarbon in source rocks and provides for the formation of inorganic oil and gas accumulations ; （ 3 ） saline deposits are favorable for the maintenance of high porosity and the formation of secondary pores and fissures in the underlying strata, but sometimes they may cause the plugging of the primary pores, and apart from that, saline deposits themselves serve as excellent hydrocarbon migration pathways or reservoir space. Their presence is regarded as an important condition for the formation of the underlying abnormally-high pressure systems, thus is favorable for the preservation of oil and gas pools ; （4） saline deposits have wonderful sealing capacity and make good cap rocks by themselves or in combination with faults; （5） saline deposits have an impact upon the regional structural styles of layers above and under it and controls over migration pathways and accumulation horizons.