Thirty percent of the deepwater wells in the western South China Sea have high-pressure and high-temperature (HP/HT) characteristics. After incorporating analyses of engineering and geological environments for deepwater HP/HT wells in the Lingshui Block, the authors suggest in the complete paper that the solution for drilling problems in deepwater HP/HT wells should start with drilling fluid. Researchers have developed a novel water-based-drilling-fluid system compatible with deepwater HP/HT wells in the Lingshui Block on the basis of a conventional drilling fluid and further optimization.
Introduction
Most of the reservoirs in the South China Sea are not only deeply buried with a low seabed temperature but also have HP/HT characteristics in the lower part of the well interval. The low temperature of the seawater environment causes an increase of drilling-fluid viscosity in the riser and deteriorates the rheology, leading to a buildup of equivalent circulating density (ECD) that might induce lost circulation.
