Laboratory Research on Properties of New Mineral Oil Drilling Fluid for Deep-water Drilling

Water-in-oil drilling fluid system was widely used in deep-water drillings.Meanwhile,rheological property of the drilling fluid and gas hydrate inhibition were the major problems in deep-water drilling,which was widely concerned.A new mineral oil drilling fluid was developed,the factors such as base oil,emulsifier kinds,organic clay dosage,oil-water ratio,and solid content,which effect low temperature flowability of water-in-oil drilling fluid were researched by testing viscosity-temperature properties of drilling fluid.Finally,gas hydrate inhibition of low viscosity mineral oil drilling fluid was studied.The results show that base oil viscosity,emulsifier kind,organic clay dosage and oil-water ratio are influencing factors of flowability of the fluid in low temperature condition,in which,base oil viscosity is decisive factor.While,influence of inactive weighting material content on thickening extent of drilling fluid in deep water drilling condition is limited.Based on these results,an optimized formula of low viscosity mineral oil drilling fluid is obtained,it includes 70%low viscosity mineral oil+30%brine+2%organic clay +3% emulsifier+0.5%wetting agent+3%filtrate loss reducer +2% lime.This drilling fluid has excellent flowability in low temperature condition,it has a stable property and good gas hydrate inhibition,it is suitable for deepwater drilling.