Study On The Fracability And Producing Limitation Of Fuyu Reservoir In Putaohua Oilfield

The Putaohua reservoirs of Putaohua oilfield have entered the period of high water cut,and the further development of those reservoirs will be harder and harder.In order to make up the decline of production,Fuyu reservoirs which have the characteristic of ultra-low permeability are being developed.However,with the characteristics of low porosity,low permeability and huge seepage resistance,the Fuyu reservoirs will have a certain deliverability only by being stimulated,such as fracturing,acidizing,etc..Therefore,figuring out the reservoir character clearly is very important for making development programs,taking effective stimulation and adopting the methods of enhancing oil recovery.So as to make sure that the reservoir will be developed scientifically and reasonably and get a better developing effect.In this paper,take Fuyu reservoirs of Putaohua oilfield as objects of study,the fracability of reservoir was evaluated with brittleness,fracture toughness,tensile strength,etc.,which based on the test of mechanical properties of rock and physical property of reservoir.The producing limitation of the reservoir was studied based on the analysis of pore throat structure and oil displacement experiment.The research achievement will have a great guiding significant on the effective development of Fuyu reservoir.The study shows that:(1)Brittle cracks are easy to form in Fuyu reservoirs,but the possibility of forming fracture network is very small.(2)The direction of the maximum of main stress in Fuyu Reservoir is N87.95°-92.45°E,and the diversity factor of the horizontal main stress is 0.29.(3)The average minimum threshold pressure gradient in Fuyu reservoirs is 0.0484MPa/m,and the average quasi-threshold pressure gradient is 0.1791MPa/m.(4)According to the difficulty of producing,the Fuyu reservoirs are divided into three types:Type ? : the permeability is greater than 1.34×10-3?m2,the oil reservoirs can be developed directly by water injection,and the injector-producer distance should be less than 150m;Type?: the permeability is 0.64×10-3?m2~1.34×10-3?m2,Water injection development can be used after fracturing,and the injector-producer distance is less than 80 m after the conversion;Type ? : the permeability is less than 0.64×10-3?m2,horizontal well multi-stage fracturing needs to be adopted in the reservoirs to effectively improve the seepage condition.