Abstract:

Putaohua reservoir is rich in oil and gas resources in the two wings of the South of Daqing Placanticline. The discovery rate of resources was low and proved reserves producing effect was poor in the two wings, because of complex oil/water distribution and inadequate understanding oil and gas accumulation pattern. Based on the detail oil-source correlation, through marking the oil-migrating faults with faults classification and analyzing the control of the allocation of faults and sand bodies to hydrocarbon migration and accumulation, the pattern of reservoirs forming is established in this paper. It's considered that the oil of Putaohua reservoir mainly comes from the local hydrocarbon source rock of K_1qn1, and the key period of hydrocarbon expulsion is the late sediment stage of K₂m and later. Consequently, the main oil-migrating faults are composed of two types:(1)faults forming in depression period and faulting in inversion period; (2)faults forming in faulted period and faulting in depression period and inversion period. The oil vertical migration to Putaohua reservoir happened along the oil-migration faults, and the distance of oil lateral migration was short because of the restriction of sand bodies scales and fault lateral sealing. Thus, the oil-migrating faults are main control faults of the reservoir, which control the oil/water distribution at plane, and the allocation of the oil-migrating faults and sand bodies controls the horizon and range of oil accumulation. The favorable area of hydrocarbon accumulation is high fault blocks next to the oil-migrating faults, including the footwall of oil-migrating faults, inversed fault terrace, monoclinic horst, and forward fault terrace.

Key words: oil-source correlation, oil-migrating fault, oil migration and accumulation, complex oil/water distribution, the South of Daqing Placanticline