High Temperature High Density Drilling Fluid Technology for the Forth Interval of Well Shengke-1.

Well Shenke-1 is an exploration well with a completion depth of greater than 7,000 m, a bottom hole temperature of 235 ℃, and bottom hole pressure greater than 100 MPa. Formations containing salt, shale and mixed gypsum/shale/salt were penetrated. Three drilling fluid formulations were applied in the fourth interval of this well. Field operation showed that these drilling fluids (polymer sulfonates inhibitive drilling fluid, high density polymer sulfonates ultra-low filtration rate drilling fluid, and ultra-high temperature drilling fluid) had very good high temperature stability, lubricity and shear-thinning properties. Effective rheology control can be easily achieved even at high solids content. Also found in field application were the tolerance to salt contamination and easy-to-formulate characteristics of these fluids.