| In China,the low permeability reservoir has large resources and great potentialities,so how to scientifically and rationally develop low permeability reservoir to obtain higher final recovery rate and maximize economic benefithas become a top priority.The Chang 3 reservoir in the Weibei Oilfield is a porous sandstone lithologic layered reservoir with micro-fractures well developed.The properties of the reservoir are low porosity and low permeability.There are no significant differences in oil and water,and there is no edge or bottom water.The saturation pressure is lower than that of the original formation.The oil well is in full fracturing production.Oil well without water production period,using advanced water injection development method,this method is good as a whole.However,there is a large difference in integrated water content after stable production,and there is a large difference in productivity between individual wells.Therefore,the evaluation of water injection development effectiveness is accurately perform will has a great significance for formulate and adjustment the development strategy for future oil fields.Based on the theory of petroleum development Geology and reservoir engineering,combined with logging data,core data and production data,this paper describes the geologic characteristics of the 3 reservoir in Weibei.On this basis,the paper first screened 8 single factor evaluation indexes of water injection effect: final recovery factor,formation energy conservation degree,water flooding reserve control degree,water drive reserve utilization level,moisture content,water retention rate,water flood index,and production decline rate.Then,the evaluation of the single factor index and the overall evaluation of the water injection effect were carried out separately.The evaluation resultsare as follows:firstly,under the existing water injection measures,the water injection effect is better and the water injection is effective.Secondly,based on the effectiveness of single-well water injection in the well group,the well components were grouped into full-efficiency wells,partial well-effective wells,and unseen wells.The dynamic characteristics of wells and single-well injection and production development were studied,and the results shows that there are differences in the effectiveness of water injection in different well groups in the study area,and there are also differences in the effectiveness of oil well water injection in the same well group.The water cut rate of the production well is close to 100% at the initial stage of production,and gradually decreases to the true initial moisture content at the later stage.Finally,this paper analyzes the reasons for the differences in water injection effects from three aspects: reservoir differences,geological factors,and fracturing effects.The study shows that the comprehensive water content varies greatly after oil wells are steadily produced,and the oil production capacity is greatly influenced by the water content.The lower the water content,the better the water injection effect;The oil wells in the high viscosity zone and the high wax content and low freezing point affect the normal production of oil well.Under similar degrees of natural fracture development,the better the physical properties of the reservoir,the higher the productivity;the more developed the main single sand layer of the well group,the better the connectivity with the well,and the greater the thickness of the connection,the stronger the oil production ability of the well group.The better the permeability,the higher the oil saturation and the better the effect after fracturing;the larger the scale of transformation,the smaller the pressure gradient of the pump is stopped,the higher the fluid production after fracturing,and the greater the amount of fluid entering the earth and the sand adding scale,the greater the daily oil production after fracturing. |
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