Stickiness Factor—A New Way of Looking at Stuck Pipe

Abstract

ABSTRACT The stickiness factor is an empirically derived number strongly related to the chances of freeing stuck pipe in a well. The number is defined by the following equation: (1)Stickiness Factor =(∡ + 10°)(OH + 5000')(MW2)×(2 + FL)(BHA+800')1×1011 where: ∡ is the maximum angle in the open hole (degrees); OH is the amount of open hole (feet); MW is the mud weight (lb/gal); FL is the API-fluid loss (cc/30 min); and BHA is the bottom-hole-assembly length (feet). The relationship between the stickiness factor and the historic chances of freeing stuck pipe is illustrated by the chance curve of Figure 1. Basically, the stickiness factor should be kept below 2.5 wherever practical. Since stuck pipe costs are largely dependent on the ability to free stuck pipe and avoid sidetracking a well, it follows that reduced stickiness factors should result in reduced stuck pipe costs. The stickiness factor is commonly lowered by reducing the API-fluid loss of the mud, reducing the bottom-hole-assembly length, or setting casing. The stickiness factor is based on a study of Gulf of Mexico wells drilled by Exxon Company, USA. Therefore, it will not necessarily apply well in other areas. The factor does. not predict when pipe will stick, but simply predicts the chance of freeing pipe that has already been stuck. The stickiness factor will also help evaluate various spotting fluids and fishing techniques since it indicates the relative difficulty (chance of success) of a soaking or fishing job. Finally, a reduced stickiness factor should reduce the chances of sticking pipe.