The Evaluation Of Surface-Active Agents For Use In The Prevention Of Differential-Pressure Sticking Of Drill Pipe

Abstract

Abstract In recent years differential-pressure sticking of drill pipe has become a very serious problem in the drilling industry. Surface-active agents are being used to a certain extent to aid in the elimination of this problem. In order to obtain a better understanding of the effect of surfactants, a laboratory investigation was performed to evaluate the efficiency of twenty various surfactant agents as to their ability to release differential-pressure stuck pipe. The surfactants tested included cationic, nonionic, ionic, and blended agents. A number of surface-active agents were found to have very favorable properties for use in this type of pipe-sticking problem. Results indicated that the proper use of surface-active agents in the drilling fluid and spotting oil would definitely aid in the prevention and release of differential-pressure stuck pipe. Introduction Drill stem differential-pressure sticking is the result of drill collars laying against the mud filter cake on the wall of the drilled hole where the existing pressure differential acting against the isolated area of the drill collars in contact with the mud cake and the friction between the pipe and the cake are too large for a direct pull to effect a release. The problem of stuck drill pipe increases as deeper wells are drilled. This is due to the use of longer lengths of drill collars, oversize drill collars, high density drilling fluids, and abnormal formation pressures which are sometimes encountered A highly permeable low-pressure zone is more susceptible for this type of phenomenon due to the mud cake deposition and pressure differential being greater in these areas. Normally, the hydrostatic pressure exerted by the drilling fluid column is uniformly distributed over the entire surface area of the drill pipe. Any restriction of uniform pressure distribution, such as that caused when the drill pipe movement ceases and the drill collars rest against the wall, creates an unbalanced hydrostatic pressure or a pressure differential, which results in a force that retains the collars against the wall of the hole and restricts pipe movement.