HIGH DENSITY SATURATED SALT-SODIUM SILICATE DRILLING FLUID TECHNOLOGY

Due to the existence of salt and gypsum in the same long section of open hole in Bachu area,Tarim Oilfield,as well as the high pressure factor,drilling fluids are often contaminated by salt and gypsum,causing downhole troubles such as pipe sticking.To solve this technical problem,a novel drilling fluid containing saturated salt and sodium silicate was developed based on the study on the working mechanisms of saturated salt and sodium silicate.Laboratory tests and field using showed that the combination of saturated salt and sodium silicate has good inhibition and can effectively reduce the solubility of gypsum and salt in water.This drilling fluid system has such advantages as good rheology,low filtration,high temperature tolerance and high salt-gypsum resistance.Its application in Tarim Oilfield minimized the occurrence of drilling problems,cut down the drilling cost,and proved its superior performance in composite salt formation.