碎屑岩输导层非均质性与油气运聚成藏

碎屑岩地层普遍具有非均质性。然而,在勘探尺度的油气运聚和成藏研究中,输导层内部成分、结构和物性等方面的非均质性被忽略,致使输导层的非均质性特征及其对地层流体和油气运聚的作用没有得到应有的重视。碎屑岩输导层的非均质性受沉积构造控制,在浅层埋藏过程中即已发生明显的差异性成岩作用,其中渗透性岩石被低渗透性隔夹层所分隔,具有一定的空间结构特征。在结构非均质性输导层中,油气运移路径的分布极不均匀,与传统上物性表现为宏观均质性的输导层模型相差甚远。结构非均质性输导层中的油气总体向上倾方向运移,在原先认为应发生垂直运移的层段运移的油气受隔夹层阻碍,运移路径变得十分复杂,侧向运移则可发生在输导层的上、中、下任意部位,但处于上倾方向的圈闭仍然是油气运移的最终指向和有利目标。在运移途中,油气可在任何地方聚集,其单个油气量较小,但数量众多,分布范围很广,总量可能远大于处于高点圈闭中的油气藏。结构非均质性输导层中,油气的运移路径和聚集方式与传统认识不同,为油气运聚和成藏过程的认识带来许多启示,勘探应该具有更为广泛的目标选择,洼陷区和斜坡区都可能成为有利勘探区域。

Heterogeneity of clastic carrier bed and hydrocarbon migration and accumulation

The heterogeneity of clastic sediments is common. However, in researches of the exploration-scale hydrocarbon migration and accumulation, the heterogeneity of the internal components, structure, and physical properties of the carrier bed have been neglected. As a result, the heterogeneity characteristics of the carrier bed and its effect on geofluid flow and hydrocarbon migration have not received the attention they deserve. The heterogeneity of clastic carrier bed is controlled by sedimentary structure. Obvious differential diagenesis occurs in clastic rocks during shallow burial. Permeable rocks are separated by low-permeability interbeds, showing certain spatial structure characteristics. In carrier beds with structural heterogeneity, the distribution of hydrocarbon migration pathway is very uneven and different from the hydrocarbon migration pathway in the traditional model of carrier bed with uniform macroscopic properties. The oil and gas in the carrier bed with structural heterogeneity generally migrates upwards. However, in the intervals where vertical migration should occur as originally thought, the oil and gas migrating is blocked by interbeds, and the migration pathway becomes very complicated. Lateral migration can occur in the upper, middle and lower section of carrier bed. Traps in the up dip direction are still the ultimate direction and favorable target of oil and gas migration. Oil and gas can accumulate anywhere during migration. The individual hydrocarbon accumulation is small in scale, but large in quantity and widely distributed, so the total amount of oil and gas may be much greater than that of reservoirs in high traps. In carrier beds with structural heterogeneity, the hydrocarbon migration pathway and accumulation mode are different from traditional understanding, which bring many insights to the understanding of hydrocarbon migration and accumulation process. The understanding of carrier beds with structural heterogeneity can provide more targets for petroleum exploration, and both subsags and slopes may become favorable exploration areas.