Development and Testing of High Temperature Resistant Composite Salt Drilling Fluid System

Abstract

In response to the difficult problem that the lithology of the target formation of Well RT1 is prone to hydrate and expand,the bottom hole temperature is high,and bicarbonate pollution is prone to occur, by analyzing the formation characteristics and technical difficulties of drilling fluids,and preferentially selecting key treatment agents such as organic salts,filtrate reducers and blocking agents,the formulation of high temperature resistant organic salt drilling fluid is developed.The results of laboratory experiments show that the drilling fluid system is resistant to temperatures up to 180℃,the difference in density between the upper and lower parts is only 0.06g/cm3 after hot rolling for 8 days,the HTHP filtration loss is less than 4 ml,the 16-hour expansion rate is only 0.88%,the secondary rolling recovery rate reaches 92%, the core blocking rate is more than 75%,and the resistance to bicarbonate contamination is more than 22000mg/L.It has good rheological properties,filtration properties,inhibition performance,plugging performance, anti-bicarbonate pollution performance and sedimentation stability performance.The results of the field experiment show that the good diameter expansion rate of the lower part of the two-open lower and the three-open lower is only 3.8%,the drilling fluid still has good rheological properties at 170℃,and the performance varies slightly when the bicarbonate ion concentration in the drilling fluid is 30230mg/L. It indicates that the developed high temperature resistant organic salt drilling fluid has effectively solved the difficult problems of easy hydration,expansion and dispersion of the mudstone in the target layer of well RT1,high temperature at the bottom of the well and bicarbonate contamination,and has broad application prospects in high-temperature deep wells.