Study On The Technology Of Seepage And Oil Recovery In Changqing Ultra-low Permeability Reservoir

At present,Changqing ultra-low permeability reservoirs have difficulties in the development of matrix flooding,and the development of injected water along the turbulent flow.After repeated fracturing,the effective period is short,and the transformation effect varies with the number of transformations,and the mechanism of osmosis in micro-nano pore-complex cracks is still unclear.Under the premise of volumetric fracturing,research on water injection and asynchronous injection and infiltration oil recovery.The water injected into the crack in three stages can not only supplement the formation energy but also rely on the sorption effect.Intrusion into the matrix,infiltration and oil production play an important role.In order to clarify the best way to seek the effect of seepage,The mechanism of volumetric fracturing stimulation in ultra-low permeability reservoirs is studied.It is believed that there are three main oil-increasing mechanisms:supplemental formation energy,oil-water displacement and improvement of oil flow channels.The impact of the process is divided into three phases.Then the numerical model of equivalent volume fracturing was established,and the crack parameters and development parameters were optimized.In medium-strong heterogeneous formations,the best combination of parameters that embody this technical advantage:a penetration ratio of 0.75,a fracture conductivity coefficient of 50μm~2·cm,a wellbore period of 30 days,and 2 to 3 rounds of water injection.At the same time,the main control factors and adaptability analysis were carried out:It is considered that the technology can effectively exert the oil-water displacement effect in the stratum with good fracturing effect,strong water wetness,high capillary pressure and good connectivity.Compared with ordinary water injection development and volumetric fracturing failure mining,the direct-to-asynchronous injection-production development after volume fracturing has the best effect,followed by volume fracturing and suction-mining technology,the main water-locking effect is caused,and it has an effective displacement basis.The reservoir is generally not recommended for water injection.The technology effectively solves the problems of rapid declining production of ultra-low permeability reservoirs,large injection-production pressure difference,seeing water multi-directionality and low-yield and low-efficiency wells,which provides a theoretical basis for the efficient development of ultra-low permeability reservoirs.