Q uantitative evaluation of parameters to characterize fault opening and sealing during hydrocarbon migration

It is critical in hydrocarbon exploration to understand the intricate role of a fault,that played during hydrocarbon migration and accumulation.And it is generally difficult to determine valid optimum parameters for the characterization of fault connectivity among numerous geological factors while quantitatively evaluating fault opening and sealing.Taking Wangjiagang oilfield in Dongying depression as a studied area,we deduced the hydraulic connectivity of fault plane during hydrocarbon migration according to the occurrence of hydrocarbon accumulation within reserviors at two sidles of faults walls and the genetic correlation between them.An index,the fault-connecting probability,was used to evaluate the possibility fault acted as a migration pathway.On the basis of fault-connectivity determination and data statistics for a typical faulted reservoir,a relationship between the index and any an individual parameter proposed in previous works to characterize fault sealing was built to evaluate the effect of these parameters in characterizing fault connecting properties for hydrocarbon migration.By compariing the statistical correlation between each of these parameters and the fault-connecting probability,we found that the effectiveness of a parameter representing only a single geological factor is generally weak to determine whether the fault acted as a migration pathway.Some comprehensive parameters that deal implicitly or explicitly with two or more geological factors,such as the shale gouge ratio(SGR),can improve the effectiveness of normal stress of a fault plane substantially.The fault opening index(FOI) may be the best parameter to characterize the fault connecting for hydrocarbon migration.