| A field use of depletion exploitation in the early, as formation pressure and Production pressure differential declining, production decline gradually. In order to make up for the extraction of crude oil caused by depletion exploitation and maintain the reservoir pressure, realize the oilfield high and stable yield, and obtain high recovery efficiency, the only way is water injection. In order to effectively utilize natural elastic energy to get the best recovery, it must choose what method of water injection and when in use of water injection. Therefore, experimental on displacement with water become the important basis for improving exploitation effect of A field.The purpose of this paper is to determine the optimal timing of water injection of A oilfield, it can provide technical support for compiling implementation to water injection plan of A oilfield, The author of this paper has carried out water flooding experiment on KH2layer of A oilfield and obtained the following understanding:1) Formation fluid of A oilfield has been combinated at first.then the experiment study on the single flash and expansion experiment and multistage degassing and viscosity-temperature.Research results show that crude oil is typical black oil,with high gas-oil ratio (111.4m3/m3),high density (0.9226g/cm3), low viscosity (2.14mpa.s), the characteristic of the large elastic expansion energy.2) The physical model of the plane visual water flooding has been made, and the water displacement efficiency and residual oil distribution under different speed are studied. Research results show that using two Wells with Parallel are generally higher recovery rate, and the sweep efficiency of horizontal well is bigger. The water breakthrough will be late if slow water flooding, anhydrous production period will be longer, and fingering phenomenon is not obvious. Howerver. because of the influence of heterogeneity of reservoir prone to premature "flooded" phenomenon with rapid water injection, make the development effect becomes poor. Waterflooding characteristic conforms to b water drive curve, it can better simulated formation conditions.3) The system test has been done on the basis of displacement experiments, mercury injection test and slice analysis research with13short of core. The research results show that porosity of KH2layer is24.7%and permeability is14.95mD on average, it belong to high permeability reservoir with medium porosity. Permeability differential of KH2layer is large and change between3.43-610mD, and pore throat sorting is poorer, micro cracks and holes development with strong heterogeneity.4) The study has been carried on oil/water and oil/gas relative permeability experiments and phase permeability prediction with9cores of KH2layer. The results show that irreducible water saturation of KH2layer change between33.4%and44.3%, the residual oil saturation change between20.2%-39.8%, the potential of water flooding is well.The irreducible water saturation of core with Micro cracks and holes development is lower, the two phase permeability area wide and oil displacement effect is better. STONE1phase permeability calculation show that the increase in gas saturation and water saturation are significantly lower the oil phase permeability, the influence of the gas is much larger than the water.5) The long core of KH2layer has been combinated and9set of constant speed under different flowing pressure displacement experiment has been done.The results show that under the same displacement speed, recovery efficiency increases with the decrease of the viscosity and formation pressure above the saturation pressure.On the other hand, the oil viscosity increase with the decrease of the ratio as gasoline below saturation pressure, but out gas played a "water plugging effect,which promoted recovery efficiency increases instead. Displacement effect is best with flowing pressure drop to50%(8.28MPa) of the saturation pressure in the displacement experiments. |
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