Development Of A New Reversible Reverse Emulsion Drilling Fluid System

With the rapid development of China's oil industry,the exploration and development of oil and gas resources has changed from conventional oil and gas field development to unconventional oil and gas field development.In the process of drilling unconventional oil and gas fields,mud shale,shale,tight sandstone and other complex strata are often encountered.When drilling with water-based drilling fluid,it is easy to have complex downhole problems such as hydration and dispersion,well wall peeling,well's diameter reduction and enlargement,and stuck drill,etc.Therefore,oil-based drilling fluid with high temperature resistance,anti-dispersion and inhibition performance,good reservoir protection and good lubricity should be applied.However,due to the oil wettability of oil-based drilling fluid on the borehole wall,drill pipe and cuttings,it is not easy to clean the drill pipe and the environment is polluted by oil cuttings.In the process of later cementing and completion,problems such as cement strength and perforation permeability decline are easy to occur,etc.Therefore,a new reversible reverse emulsification drilling fluid system was developed to solve the above problems.By studying the mechanism of reversible reverse emulsifier,the molecular structure of the emulsifier was designed.Using palmitic acid(C16)and amino ethyl ethanolamine as raw materials and KOH as catalyst.Emulsifier EMUL-GP for reversible reverse-emulsifying drilling fluids was synthesized by amidation reaction under optimized reaction conditions such as reaction time,reaction temperature and dosage.The effects of the amine value,viscosity,HLB value and emulsifying temperature,etc on emulsifier were analyzed.Emulsifier EMUL-GP was combined with sodium alkylbenzenesulfonate to analyze the effect of mixed emulsifier HLB value on emulsifying stability and the reversibility of emulsion.Based on the optimization experiments of oil phase,oil-water ratio,addition of emulsifier and organic soil,etc,the optimal formula of reversible reverse-emulsifying drilling fluid system was determined to be:7#white oil+CaCl2 solution+4%mixed emulsifier+3%organic soil+3%filtration reducer+4%CaO+barite,oil-water ratio 7:3,with a density of 1.2g/cm3.The sedimentation stability,rheological property,high temperature aging resistance,pollution resistance and hydration dispersion inhibition of the system were evaluated.The results show that the reversible reverse emulsification drilling fluid system performs well.The reversible reverse emulsification drilling fluid system developed in this paper can provide technical support for the development of unconventional oil and gas Wells and shale gas horizontal Wells,etc.