Study On Effect Of Suspension Particle Of Water Injection Towards Ultra-low Permeability Reservoir

Water injection is commonly used in present oilfield exploitation. Injecting unqualified water will cause damage to reservoir and for low permeability oilfield, the damage will be more severe.In this paper, cores from Yushulin Oilfield and the 5th Daqing oil production factory were selected for rate-controlled Hg penetration tests. The test results show us the pore throat distribution and the average throat size of the cores from the two reservoirs. Permeability decline caused by suspension of same size and different concentration and by suspension of same concentration and different size is separately studied through laboratory injecting water experiments. Permeability decline increases as concentration of suspended particles increases and as size of suspended particles increases when cores have similar characteristic. A boundary line of 30% is determined to determine the required concentration and size of suspension in water injection. The boundary line of suspension for cores whose gas permeability is 1.0mD in Yushulin oilfield is:0.5mg/L and 1μm. The rate-controlled Hg penetration tests are combined with laboratory injecting water experiments to set up a simulation of suspension particle blocking based on previous theories. The simulation is applicable for ultra-permeability reservoir and further verified by experiments. Results from experiments of same-size produced water show permeability loss of cores of 0.5mD is smaller than those of 1.0mD. Application of the simulation in experiments of produced water injection proves the concentration of produced water smaller than 3.0μm too low cause permeability loss larger than 30%. Therefore, the present standard of water injection is applicable.