An Ultra-high Density Diesel Oil Base Drilling Fluid for Use at 160℃

Increasing demands of oil worldwide is driving oil and gas exploration and development to deeper and unconventional petroleum reservoirs, and high temperature ultra-high density oil base drilling fluids are required to drill the wells. The high temperature ultra-high density oil base drilling fluids should have good rheology, low HTHP filtration rate, good plugging performance and good dynamic/static settling stability. An ultra-high density oil base drilling fluid used at 160℃ has been developed in laboratory. large amount of experiments show that, using barite, an ultra-high density diesel oil base mud with good rheology and good dynamic settling stability cannot be obtained. The composition of the ultra-high density diesel oil base drilling fluid, with its density changing from 2.4 g/cm³ to 3.0 g/cm³, is as follows:0^# diesel oil and 25% CaCl₂ water solution in a ratio of 90:10 as the base fluid, organophilic clay, 0.8% primary emulsifier, 1% secondary emulsifier, 1% wetting agent, 5% filter loss reducer, 3% CaO and weighting agent (Barite:Micromax=6:4). The concentration of the organophilic clay decreases with density; density of 2.4 g/cm³, 2.6 g/cm³, 2.8 g/cm³ and 3.0 g/cm³ corresponds to the optimum organophilic clay concentration of 1%, 0.5%, 0.3% and 0%, respectively.