Characteristics Of The Power Of Hydrocarbon Vertical Migration, The Passage System And The Formation In Eboling Area Of Qaidam Basin

Hydrocarbons are not directly become accumulations after they were expelled from source rocks, they need powers, pathways and traps for migration. Among them, the pathways for vertical migration are necessary and it is need to be carefully studied of with their regularities of distribution. Then the foundation of the whole hydrocarbon migration and accumulation researching would be laid.The major migration power in this area is overpressure. It could be calculated by basin numerical simulation to get the overall underground overpressure evolution history and specific values. And then to aim at the last pool-forming period when developed the gas accumulating pattern nowadays, the last phase of N23, to summarize the distribution of overpressure that time.The main vertical migration pathways in this area are open faults, which determined by the non-dimensional parameter named FOI (Fault Opening Index). In addition, there are thick sand layers in some structures and they can also act as vertical migration pathways. The major lateral migration pathways are cross connected sand layers and plane of unconformity. These pathways constitute the passage system in this area.Under the influence of the factors above, gas could be able to migrate to the vicinity of open faults along the plane of unconformity after they were expelled from source rocks. Then it enter the vertical migration pathways and migrate up to the top of faults by the driving from overpressure, and turn into sand layers intersected by the faults. After that, gas continue migration along these sand layers into favorable traps in each structures to accumulate.