Most offshore drilling operators have experienced unique physical drilling problems whilst operating in the coastal waters of the British Isles and North Sea areas. The magnitude and effect of each problem is often novel, requiring specific corrective action. Improved physical techniques and chemical treatment are physical techniques and chemical treatment are continually being sought to provide an interim or permanent solution. This paper traces the development and application of a drilling lubricant which has been extensively utilised to overcome the problems of downhole torque and drag encountered in drilling deviated wells. The lubricant, which is based on a vegetable oil derivative, is added to a water based drilling fluid system to provide a significant reduction in torque and friction without creating secondary well problems. A technique which presents several associated problems is drilling directional wells. Directional drilling has problems is drilling directional wells. Directional drilling has been universally applied, and holes with deviated sections greater than 70 degrees have been successfully, completed. This beneficial drilling technique has introduced several undesirable features requiring corrective action, i.e.:downhole torque:drag: . stuck-pipe:
Downhole torque is usually produced by a combination of the drill pipe rotating on the side of the hole. (either open or cased sections) the angle of deviation, the friction at the bit and the general requirement for extra stabilisers and 'dog- legging' of holes after correction runs. In deviated drilling all of these effects cause greater contact of drill stem to hole, and hence greater torque and increased probability of resultant stuck pipe. The standard solution for most of these problems is to incorporate diesel oil or lubricity additives into the drilling, fluid. Diesel oil often does not provide a satisfactory solution to these drilling problems.
