Abstract:

It is one of the new advances in reservoir geochemistry to study leakage of fault with geochemical techniques.According to the distribution of n-alkane and the characteristics of biomarkers,there exist 5 types of crude in Kokyar oil reservoir,including original-state oil,residual oil from fractionation through migration,condensate and light oils from evaporation and retrograde condensation,residual crude from gas washing,and crude with wax crystallization.The second type of crude is mainly distributed on the top of the structure,indicating that leakage occurred along small faults and the top of the structure,leading to the obvious difference between ancient and present OWC.Moreover,molecular geochemical analysis of the crude verifies that crude on the top of the structure have relatively higher maturity and higher contents of heavy components and those uneasily to be migrated.

Key words: fault sealing, leakage of reservoir, Kokyar, reservoir geochemistry