Laboratory Study of the Heavy Weight Reversible Invert Emulsion Drilling Fluid

A novel reversible invert emulsion drilling fluid which is useful in resolving the contradiction between drilling efficiency, cementing and environmental effect has been invented based on the protonation reversibility of amine. The new drilling fluid has reversible emulsion-phase behavior. The formulation of the reversible invert emulsion drilling fluid was: white oil (5)+25% CaCl 2 brine+50% weight agent ZFU-3+1.5% organoclay+0.5% lime +4.5% reversible emulsifier UPSG-1+1% wetting agent DYSL-3+an appropriate amount barite, oleaginous fluid to non-oleaginous fluid-ratio was 50/50, drilling fluid density was 1.9 kg/L, weight agent ZFU is sodium formate. Comprehensive performance evaluation with laboratory test showed that the new drilling fluid could be readily and reversibly converted from a water-in-oil emulsion to an oil-in water emulsion and back to a water-in-oil emulsion using an acid-based chemical switch. And before and after converting the emulsion mud maintains good performance, with emulsion-breaking voltage of 900-1,100 V, resistance to temperature of 150℃, HEHP filter loss of less than 6 ml. Additionally, the filter cake and oily cuttings could be treated easily. This suggests that the reversible invert emulsion drilling fluid has both merits of oil-based fluid and water –based fluids, and all properties are excellent. The reversible invert emulsion drilling fluid is capable of resolving the problems with the application of conventional oil-based drilling fluid. The density of the reversible invert emulsion is 1.9 kg/L, which is also better than the traditional reversible invert emulsion drilling fluid.