| The heavy oil resources in China are expected to be recoverable reserves of 300 x 108 t,but it is difficult to exploit.Because of high viscosity,poor fluidity,heavy components,In the process of development,sand production,oil and water emulsification,well bore wax and other problems often happen,resulting in economic losses caused by the decline of production capacity.Therefore,it is very important for offshore oilfield to protect heavy oil reservoirs and maintain stable production and increase production.The Minghuazhen Formation of LD27-2 oilfield is unconsolidated sandstone heavy oil reservoir,the.The regional geological characteristics of oil field are complex.and some problems such as the rapid decline of production capacity in the early stage of the production of oil well,oil well sanding,the rapid increase of water content and so on.Aiming at these problems,this paper selects LD27-2 heavy oil reservoir of Minghuazhen Fonnation as the research object,on the basis of the extensive literature survey and reservoir geology and fluid characteristics and production performance data,combined with the theory and laboratory experiments,using high pressure mercury,cast thin section,scanning electron microscope,nuclear magnetic resonance,XRD,coreflooding microscope observation and other means,to analyze the impact of changes in the nature of reservoir rock and fluid properties on well production.The research contents include reservoir lithology,physical property,pore throat structure,reservoir sensitivity,compatibility of injected water with formation water,and oil emulsification jam,etc.The paper clarifies the reasons for the decline in the production capacity of LD27-2 oilfield,and recommmends the measures of injecting low salinity water to achieve the purpose of controlling the water and increasing the oil.The paper obtained the following results and knowledge(1)The upper part of the reservoir in minhuazhen Formation of LD27-2 oilfield is the meandering river deposit,the lower part is the delta front sedimentation,and the lithology is mainly composed of fine-medium grained debris-arkosic sandstone,argillaceous consolidated unconsolidated sandstone,minhuazhen Formation mainly primary intergranular pore,pore throat connectedness is good,the average porosity is greater than 30%,the average permeability over 1000 mD,belong to high pore type high permeability reservoir.(2)The results of sensitivity experiments show that the sensitivity of existing velocity sensitive damage medium weak-medium strong reservoir,and established the use of production performance curves to determine the velocity sensitivity on identification parameters and methods of production,the recommended calculation method of critical production rate of oil well;water sensitivity is from medium to strong,critical salinity is about 20000mg/L reservoir stress sensitivity is strong,and recommends reasonable production pressure difference.(3)Through the typical wellhead production fluid observation,,combined with laboratory analysis the relationship between water content and emulsion rheology.It is found that when the water content of crude oil is about 50%,the viscosity of the produced liquid is the largest and the crude oil emulsification is the most serious.Through the dynamic production curve statistics,it shows that the influence degree of crude oil emulsification on the decline of productivity is between 20%?30%.(4)Based on the characteristics of the reservoir of the Minghuazhen Formation proposed the low-salinity water flooding technology,we combine theoretical analysis with experimental research to study the influence of the injection of low salinity water on reservoir oil-water and rock.It was clear that low salinity water flooding could reduce the permeability of reservoir water,increase oil phase permeability,change rock wettability,and expand the effect of water injection wave and surface,which is a new technology of controlling water and oil increasing with great potential. |
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