Analysis On Main Controlling Factors For Oil Accumulation In Chuan 46 Area From Chuankou Oilfiled

The study on controlling factors and accumulation mechanism of low permeability reservoir formation is a hot and difficulty research issue in recent years. The formation of Chang 6 and Chang(4+5) 2 in Chuan46 well area, ChuanKou oilfield, is a typical low-porosity and low-permeability reservior, with great variation in oiliness of reservoir, abnormal differential phenomenon of oil and gas,which causes the difficulty in exploration and exploitation.Because of inadequacy recognition on controlling factors and accumulation mechanism of oil, we have no clear understanding and further study on oil and gas abundance law. Therefore, this paper not only conducts the deep research to pool-controlling factors of this area,but also provides important reference value on exploration and exploitation of the same type reservoir.The sedimentary facies were analyzed systematically based on drilling, logging and other exploitation data,; after obtaining the total erosion thickness of Chang 6 in main accumulation period(at the end of Early Cretaceous epoch),the superface microstructure is restored by using stratigraphic contrast method. And equivalent depth method was used to resume overpressure at the time of largest burial depth. Then the primary migration orientation of hydrocarbon which was drived by paleo-pressure was analysised and hydrodynamic force distribution was reconstructed.Lastly, jiont the regular pattern of oill and oil-water distribution characteristics, the controlling factors,accumulation mechanism was generalized of study area..The results show that:top structure of Chang6 Member Chuankou oilfield chuan46 area Presented "south high north low" pattern, and developed two nasal shape apophysis. Sedimentary microfacies of Chang6 Member are underwater distributary channel and underwater distributary interchannel, Chang4+5 Member paragraph 2 are distributary channel and distributary interchannel. Overpressure occurs from Chang 6 in Chuan46 well area, ChuanKou oillfield. But the values of overpressure in study area are smaller than those in other area of Ordos basin. The majority of values are less than 1 Mpa. The overpressure values reach the peak in Chang 7. Those are mainly concentrated on 4-5 Mpa. The overpressure difference between Chang 7 and Chang 6, that is between source rock and reservoir, are more than 0.23 Mpa capillary resistance Which hydrocarbon migration has to overcome, and difference offer sufficient dynamic force. At main accumulation period, the oil potential distribution of Chang 6 is higher in northwest than it is in southeast, indicating hydrocarbon migration direction is from northwes,northeast,southwest to southeast. Lateral migration in north of study area is restricted by changes of sedimentary facies, hydrocarbon accumulation is mainly controlled by sedimentary facies. hydrocarbon accumulated from higher potential to lower potential and enriched in nose structure, that is hydrocarbon accumulation in north of study area is controlled by oil potential and microstructure.