Research On High Temperature Resistant And High Density Oil-based Drilling Fluid System

Compare with water-based drilling fluid,oil-based drilling fluid is used in complex oil and gas wall drilling because of it's strong inhibition,temperature resistance,lubricity and anti-pollution ability.At home,emulsifier,fluid loss additive,rheology modifier,organoclay and wetting agent is the basic treatment agent in oil-based drilling fluid system.The emulsifier is mainly polyamide and the fluid loss additive is asphalt,but the phenomenon of high temperature viscosity increase,influence the rheology of system,and is limited in the process of asphalt.In order to solve the problem of increasing viscosity of asphalt fluid loss additive in oil-based drilling fluid,through the investigation of home and foreign literature,based on the mechanism of fluid loss additive,combined with the knowledge of organic chemistry,a polymer fluid loss additive for oil-based drilling fluid was synthesized by dispersion polymerization using acrylamide(AM),steryl methylacrylate(SMA).The single factor experiment method was been used to optimize the reaction condition by measuring API filtration loss of drilling fluid system.The test results revealed that product was stable at 160?,and has little effect on the rheology of oil-based drilling fluid system.Based on the synthesis of fluid loss additive,emulsifier,rheology modifier,organoclay and wetting agent have been preferred and determined optimal dosage.Finally,oil-based drilling fluid system is formed(O/W=8:2,0#diesel oil+25%CaCl2+3%Emul-3+1.5%Smul-1+2%Wet-4+1.5%Gel-3+3%rheology modifier1?+3%FLA+2%CaO+barite.The performance of oil-based drilling fluid system with different oil-water ratio and density is evaluated,the result show that the density of system has a wide range of application,with the decrease of oil-water ratio,the viscosity of system increase and the rheology becomes worse.The effect of different activity calcium chloride aqueous solution and different type of salt solution as internal phase of oil-based drilling fluid was evaluated.The experimental result show that,with the increase of the concentration of the calcium chloride aqueous solution,the water phase density increase,the water phase activity decrease and the viscosity of system increase,the concentration of calcium chloride aqueous solution in high density system should not be too high.Compared with calcium chloride aqueous solution as the internal phase of oil-based drilling fluid,the viscosity of system formed by calcium bromide aqueous solution is higher,and the performance of oil-based drilling fluid system formed by potassium formate aqueous solution is the worst compared with the first two systems,and the system is unstable.