Research On Fault Systems And Reservoir-controlling Mechanisms Of F,Y Oil Layers In Sanzhao Depression

Daqing oilfield exploration and development of the external focus in the east of the placanticline and placanticline, the main purpose formations are the Fuyu and Yangdachengzi formation. The Fuyang formation of Sazhao depression experienced a pre-exploration, evaluation, the pilot phase, and the proved oil-bearing area is 304.97 km², proved geological reserves is 17130.7×10⁴t, unproduced reserves is 15,932×10⁴t. Overall performance as' low rate of proved resources', ' low rate of the using of proved reserves ' characteristics. As a major future production, the evaluation intensity of Fuyang formation increases year after year. Although through the reservoir description and placing of wells optimization in the early-stage of the development, the success drilling rate of Fuyang formation remains low, the main reasons are drilling water sand or poor abandoned reservoir. The main reason of the low success drilling rate is complex geological conditions of Fuyang formation, mainly in the following three aspects: First, fault system is complex; Second, Fuyang formation of Sanzhao depression lay in the intersection of the source area, the distribution of river is unclear; Third, it is both time and space coupled with the complex relationship between oil and gas accumulation. Based on the three major contradictions of the Fuyang formation oil and gas accumulation, change the traditional model of petroleum geology, start from the fault system, analysis the relationship between fault and sand, and the oil and gas, explore 'fault system using' method to finding oil. In this paper, based on the comprehensive collection of seismic, well drilling, testing for oil and development dynamic data of Sanzhao Depression Fuyang formation, we analysis faults growth characteristics, the action law and evolution history, analysis fault control reservoir mechanism and regular pattern of rich oil and gas concentration, and define the next step exploration direction of Fuyang formation.The characteristics of faults in F,Y oil layers are that the strike is main of NW, the scale is primarily small, the density is big, the plane distribution is uneven, the fault combination type diverse and they crowded distribute as belt. The belts of faults which strike is NNW and NNE are the result caused by the fundamental faults and Cable-Stayed role (twisting); The belts of faults concentration have different genetic mechanisms: submeridional zone of faults are the cause of synthetic listric fundamental faults and their horizon decoupling function;. The belts of faults which strike is WE are the "regulation" belts of faults caused by differential extension function. The faults in Sanzhao depression are formed in 7 period: Initial early Cretaceous, the period of qn1 sedimentary, the period of Yaojia formation sedimentary, the period of n1 and n2 sedimentary, the last period of Nenjiang formation, the last period of Mingshui formation and the last period of Paleogene 1pK7(?) EK3R_? .It is thinked that F,Y oil layers are constituted by faults of 4 differential activity rule based on faults activity periods, which are formed in downwarping period, in downfaulted period keeping activity in downwarping period, in downfaulted period keeping activity in downwarping period and reversal period, and in downwarping period keeping activity in reversal period. The 3 type and 4 type of all the 4 types faults are which connect source rock and reservoir, and most of them are boundary faults of belts of fault zone. Based on the establishment of "single-sand" equitime formation framework of F1 oil group in Sanzhao depression, it is thinked that the mainly distribution of channel sands is EN, the faults which connect the source rock and reservoir are mainly SN, and oblique crossing of river and faults is favorable to form fault -lithologic traps. Belts of fault zones are not the main full oil structure. It is the first time to state that oil mainly accumulates in the footwall channel sand of the oil sources faults; belts of fault zones are the fault of "v" shaped "graben", and they are the construction of relatively low position; the oil sources faults are most the boundary faults, belts of fault zones are not the directed zone of oil-gas migration, and oil mainly migrates to the low plates which have Smaller resistance. Wherefore, the footwall channel sand of the oil sources fault are the main enrichment regional, and the "horst" which controlled by the oil sources fault is favorite to accumulate. It is proposd "59 evaluated target zone", which further clarified the next target for exploration, according to the principles of "avoiding fault-zone, in graben or horst which controlled by the oil sources fault" to look for favorable evaluation district.