| In the petroleum industry,oil-based drilling fluids are widely used because of their strong anti-pollution ability and shale inhibition.But it is not compatible with cement slurry because of its lipophilic nature,which makes cementing difficult.A solution that has been experimented and discovered before the cement job is the injection of flush fluid,which isolates and cushions the drilling mud,thereby improving cementing efficiency.Based on the domestic and foreign research present situation,discovered the cementing rinses selective smaller,less species,and currently used in oil industry is drilling cementing rinses research,mainly concentrated in the cementing rinses formula optimization,washing fluid for well cementing evaluation,mostly confined to characterize the flushing efficiency,lack of cementing rinses toxicity evaluation indicators,there is no systematic study on the comprehensive evaluation system of cementing flushing fluid.This paper focuses on the development of a simple preparation process,high efficiency of oil-based drilling flushing fluid products,pay attention to the impact of flushing fluid on the ecological environment,and finally establish a comprehensive evaluation system of oil-based drilling flushing fluid including the efficiency of flushing,environmental friendly characteristics,compatibility and compressive strength.The following conclusions are drawn through the research.An oil-base drilling fluid flushing fluid was developed,which was composed of nonionic surfactant and inorganic salt washout aid.The factors affecting the efficiency of the oil-based drilling flushing fluid were optimized by using single factor analysis and response surface methodology.The optimal formulation of the developed Flushing Fluid is: 2.5% X1+2.5% X2+0.5% X3+0.5% X4.The flushing effect of oil-base drilling fluid is very remarkable.Using six-speed rotary viscometer to wash 60 s under300 r/min condition,the measured flushing efficiency can reach more than 98%.Based on the existing evaluation methods for the efficiency of flushing fluid,a set of practical and efficient method for measuring the efficiency of cementing flushing fluid has been formed,which can be quantitatively analyzed by subtracting the difference of material balance.The overall appearance of the flushing fluid is milky white,p H 9.2,density1.01g/cm3,plastic viscosity 5.3 MPa,shear force 0.9709 Pa.The rinsing fluid has good wetting and spreading ability,which ensures the quality of cementing interface.The rinsing fluid system is similar to Newtonian fluid and has good flow performance.When using saline solution with salt content of 6.5%,the flushing efficiency can reach95.90% at normal temperature,which can meet the construction requirements of special areas with high salt content.After being refrigerated at 4? for 10 days,the oil-based drilling flushing fluid has no delamination and can adapt to the low temperature environment successfully.The Zeta potential values of 0.6%,6.0% and 30% flushing fluids were-2.826 m V,0.378 m V and 1.464 m V,respectively,indicating that the 0.6%cementing flushing fluid system had the best stability.The flushing efficiency is above96% in the range of 25?100 ?.The addition of 5% flushing fluid will not prolong the thickening time of cement slurry or reduce the compressive strength of cement.The mixture of flushing fluid,drilling fluid and cement slurry has good rheological compatibility with the compatibility degree R < 0.The results of various toxicological tests,including earthworm acute toxicity test,seed germination test and pot experiment,showed that the cementing fluid would not pose a threat to the survival of earthworms when used at 6000mg/kg.It is safe to germinate wheat seeds when the concentration is below 3000 mg/kg.When the concentration was below 10000mg/kg,the contents of chlorophyll and carotenoid in wheat were not significantly reduced in pot experiment,so it would not threaten the normal growth of wheat.The oil-based drilling flushing fluid is an eco-friendly preparation and has no obvious harm to the ecological environment within the range used.The 10-fold flushing isolation concentrate was prepared by industry.Five parts X3 and five parts X4 were added into 100 parts tap water in turn according to the number of parts by mass.The mixture was stirred by a high-speed disperser with a stirring rate of 200 RPM and a stirring time of 15?20 min.After dissolution,27.5 parts of X2 were added at the stirring rate of 500 rpm and stirring time of 10 min to obtain a milky solution.Add 27.5 parts of X1 and mix well at the stirring rate of 300 rpm and stirring time of 10 min.Finally,a 10-fold concentrate of flushing fluid for oil-base drilling fluid was obtained.The p H value of the oil-based drilling flushing fluid prepared by industry is 9.5,which has good stability and is easy to dissolve in water.The flushing efficiency measured by industry sample can reach more than 98%. |
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