Control Effect Of Normal Fault Related Folds To Hydrocarbon Migration And Accumulation

It has been a common phenomenon that hydrocarbon accumulating nears the faults with the development and exploration of oil and gas. This paper based on the phenomena of “oil different accumulation nears faults” and “oil different accumulation inside and outside fault zones”, carrying out the theoretical research of the normal faults formation and growth characteristics, and the stratum deformation during its activities, and then classifying the normal fault-related folds in extensional settings according to folds genesis and describe their geometry and distribution characteristics. Finally we expound the control effect of normal fault-related to hydrocarbon migration and accumulation through “normal fault-related folds provides traps for oil accumulation” and “use normal fault-related folds to determine oil source faults” these two aspects.Geometric characteristics of normal faults will changes when some other factors change during the period of its formation and development. Differential compaction and variation of lithologic mechanical strength can cause change of faults dip to produce listric or anti-listric normal faults; and the displacement gradient which faults has the max in the middle and gradually reduce towards the tips along the fault trace、fault plane and be perpendicular to the fault plane can generate strata curve, these characteristics are the reasons of the normal fault-related folds. This paper classifies the folds into three according to the formation and growth of faults: fault plane dip variation related folds namely rollover; fault displacement gradient related folds which includes drag folds、reverse drag folds、transverse displacement gradient folds and propagation folds; compound type folds mainly formatted in the fault segment mode.Normal fault-related folds which form before the hydrocarbon expulsion can provide effective accumulation trap for oil; because of the advantage that near faults these folds can collect the oil which migrate by faults immediately. On the other hand, using normal fault-related folds to determine oil source faults in this paper can help eliminate the affection of weak activity normal faults.