断裂输导油气运移特征及其能力

HYDROCARBON MIGRATION CHARACTERISTICS AND ABILITY THROUGH THE FAULTS

为了研究断裂在油气成藏中的作用,采用理论和油田实际相结合的方法,对断裂输导油气机制及特征进行了研究。结果表明:并不是所有断裂均可以作为油气运移的输导通道,通常只有长期发育的断裂才是油气输导运移的通道;断裂输导油气的动力主要是压力差,地层超压和浮力也可起到一定的作用,输导通道主要是断裂带内的诱导裂缝,其发生在源岩大量生排烃期之后的断裂活动时期内;断裂输导油气运移的能力主要受到自身发育特征和与区域应力关系的控制,断裂延伸长度、倾角、密度越大,走向与区域主压应力方向之间夹角越小,断裂输导油气运移动力越强,反之则越弱;断裂向上输导油气运移层位除了受到断裂向上延伸层位的控制外,更受到被断裂错断区域性盖层厚度和其上下地层砂地比的制约,区域性盖层断接厚度大,油气不能穿过其向上运移,在区域性盖层之下高砂地比地层中侧向分流运移,反之则在区域性盖层上下高砂地比地层中侧向分流运移。

In order to study the role of faults playing in oil and gas accumulation, oil and gas migration mechanism and characteristics through the faults are studied by using the method combining the theory and oilfield practice. The results show that not all faults are transporting pathways for the oil and gas migration. Only long-term developed faults are the transporting channels the migration. The power of the oil and gas migration through the faults is mainly pressure difference, the overpressure in strata and buoyancy also play some roles in the migration. The transporting Pathways of the oil and gas through the faults are the induced fi＇actures in the fault belts. The transportation is active after a lot of oil and gas expelled from the source rock. The migration ability through the faults is controlled by the developed characteristics of the faults themselves and the relationship between them and the regional stress. The bigger the faults＇length, the dip angle and density are the smaller the angle between the fault trend and direction of main regional stress will be, the stronger the migration ability through the faults will be, on the contrary, the weaker the migration ability will be. The migration through the faults is controlled by the thickness of the faulted regional caprock and the sandstonestratum ratio besides the control of the horizons with upward faults. If the connected thickness of the faulted regional caprock is big, the oil and gas can not migrate upward through the caprock, the hydrocarbon is prone to divert and migrate laterally into the stratawith the high ratio beneath the regional caprock, on the contrary, the petroleum can penetrate the caprock, divert and migrate laterally into the strata with the high ratio.