Research On Organic Plugging Removal Technology For Heavy Oil Wells

The quality of global crude oil is getting heavier and heavier,and the proportion of heavy oil in the proven reserves of world oil and gas resources is increasing year by year.However,due to blockage near wellbore in heavy oil reservoirs,it is increasingly difficult to exploit heavy oil resources.Chemical plugging removal technology,such as conventional acidification,is limited by the field because of its high requirements for equipment,corrosion pipelines,difficult treatment of back-flow fluid,etc.Therefore,in-depth study of organic plugging removal technology in heavy oil reservoirs is one of the effective methods to solve the current problem of shortage of oil resources and achieve efficient development of heavy oil resources.Heavy oil resources are widely distributed in China.Land heavy oil resources are mainly distributed in Xinjiang,Shengli,Liaohe and Henan oilfields,while offshore heavy oil resources are mainly distributed in the Bohai Sea.Based on the basic information of the target reservoir,combined with the analysis of the plugging removal mechanism of heavy oil wells,and according to the existing plugging removal technology,the organic plugging removal system of L oilfield in Bohai Sea region is studied in this paper.The specific research contents are as follows:(1)Based on the result of X-ray diffraction,scanning electron microscopy and field feedback data,the lithology and mineral composition,formation and fluid physical properties,reservoir temperature and pressure characteristics of the target oilfield reservoir are defined;the description of basic characteristics of heavy oil and oily sludge and determination of their component content are completed according to laboratory experiments,and the cause of blockage in the vicinity of heavy oil wells is analyzed;the theory of "similar dissolve mutually,emulsification and viscosity reduction" is combined;and adhering to the idea of"heavy oil dissolution,oliy sludge dispersion and overall viscosity reduction",it provides sufficient theoretical basis for the development of organic plugging removal system.(2)Based on the characteristics of heavy oil and oliy sludge in the target reservoir of heavy oil reservoir in L oilfield,a composite organic plugging removal system consisting of organic solvent system,heavy oil viscosity reduction system and additives was developed by fully and reasonably utilizing the beneficial synergistic effects of solvent and organic viscosity reduction system.The system can dissolve heavy oil and oily sludge efficiently and quickly,strip and disperse organic heavy components such as resin asphalt adhering to the surface of oily sludge,and make the viscosity of heavy oil decrease sharply.(3)The optimum dosage of organic solvent system and organic viscosity reduction system in the composite organic plugging removal system was optimized through laboratory experiments.The composition of the formula system and its compatibility with additives and formation water were evaluated.The swelling capacity of the system to rubber products such as sealing rings and gaskets and the dynamic flow plugging removal effect of the system to artificial cores were also evaluated.The experimental results show that the formulation system has good compatibility with additives and formation fluids,and the solution is clear and transparent without flocculent precipitation;it has no obvious swelling effect on rubber products,and can be tested in situ;its recovery rate of artificial core permeability is up to 244.4%.(4)According to the comprehensive performance evaluation results of the composite plugging removal system the corresponding construction technology was formed and the related parameters were calculated and optimized.The organic plugging removal technology for heavy oil wells in L oilfield was formed,which enriched the series of offshore heavy oil reservoir plugging removal technology.Field test results show that the composite organic plugging removal system can effectively relieve the blockage damage of heavy oil wells in L oilfield.After the measures,the liquid production of shut-down wells recovers to 25 m3/d,and the oil production recovers to 10 m3/d.The plugging removal system has remarkable effect of increasing fluid and oil production,and has achieved the anticipated effect of plugging removal and viscosity reduction.