Study on a New High Temperature High Density Saltwater Drilling Fluid

Many problems exist in the use of high temperature high density saltwater drilling fluids, such as more additives (both type and quantity) that are used than necessary, HTHP filtration rate and rheology after aging becoming difficult to control, and high costs in mixing and maintaining the property of the drilling fluid, etc. The reasons that these problems have been studied for a long term but remained unresolved are analyzed in this paper, and based on the analyses, a method has been presented to resolve the high viscosity, high HTHP filter loss and difficulties in controlling the properties of the drilling fluids, problems that are associated with the use of high density drilling fluids. This method, based on the high temperature crosslinking of mud additive, resolves the problems through optimized sizing of barite particles. A new technical clue has been presented for the study of high temperature high density saltwater drilling fluid, and based on the technical clue, a high temperature high density saltwater drilling fluid with excellent performance (low HTHP filter loss, good rheology…) was formulated with only 4 kinds of additives whose total amount was only 1/2-1/3 of the total amount of additives used in the high temperature high density saltwater drilling fluids presently in use. The high temperature properties of this new drilling fluid had the potential of becoming better after long time of using, and being easy to maintain. The study conducted and the drilling fluid formulated have provided a way of resolving the stubborn problems associated with the use of high temperature high density saltwater drilling fluids in China.