相-势-源复合控油气成藏机制物理模拟实验研究*

含油气盆地的地质相、流体势、烃源灶是影响圈闭含油气性的决定性因素, 三者缺一不可。在各要素满足控藏临界条件下, 优相-低势-近源复合指数(FPSI) 越高, 圈闭含油气性越好。基于相-势-源复合控油气成藏机制开展物理模拟实验研究, 结果表明:“源”控制着油气成藏的物质来源, “相”控制着油气成藏的孔隙空间、“势”控制着油气成藏的运移动力, 当三者联合作用时能够形成油气藏。实验结果还表明, 圈闭外部(盖层)岩相和圈闭内部(储集层)岩相粒径差别越大, 越有利于油气在毛细管力作用下从细粒低孔渗的围岩之中进入到粗粒高孔渗的储集层之内聚集成藏, 临界条件是：圈闭外部围岩颗粒粒径较圈闭内部储集层颗粒粒径小2倍以上, 或外部毛细管力较之内部大2倍以上, 也即外部界面势能较内部高2倍以上；圈闭外部烃源岩含油气饱和度越高, 越有利油气进入圈闭内部储集层中聚集成藏, 临界条件是外部源岩的含油气饱和度达到和超过5％。

Physical simulation experimental study on mechanism for hydrocarbon accumulation controlled by facies-potential-source coupling|

Facies, potential and source rocks of petroliferous basins are three factors controlling the traps petroliferous property, they are necessary for reservoirs to trap hydrocarbons. Under the condition that they all met their own critical conditions of controlling reservoirs, the larger the facies-potential-sources coupling index, the higher the petroliferous property of the trap. Based on the mechanism for hydrocarbon accurnulation controlled by facies-potential-source coupling, physical simulation experiment was conducted. Studies showed that sources controlled the material origin of hydrocarbons, facies controlled the pore space to store hydrocarbons, and potential was the driving force for hydrocarbons to accumulate in traps. Only when they combined with each other, could hydrocarbon reservoirs form in basins. Furthermore, the larger the grain size difference between cap rocks outside the trap and the reservoirs inside the trap was, the easier it was for hydrocarbons to migrate from wall rocks of fine grains and low porosity to reservoir of coarse grains with high porosity. Meanwhile, its critical condition was that the ratio of grain size of reservoir to that of wall rocks was larger than 2 times, or the outside capillary force was more than 2 times larger than that inside the traps. At the same time, high petroliferous property of source rocks was better for hydrocarbons to accumulate in the traps|with hydrocarbon saturation of outer source rock reached or more than 5% as the critical condition.