engleski

Spotting Fluids for Freeing Differentially Stuck Pipe

Differential sticking is, for most drilling organizations, the greatest drilling problem worldwide in terms of time and financial cost. Differential-pressure pipe sticking occurs when a portion of the drill string becomes embedded in a filter cake that forms on the wall of a permeable formation during drilling. The dominant force is usually associated with a difference in pressures between the hydrostatic pressure of the mud and the pore pressure in the contact area, though adhesion and cohesion may also contribute some resistance to pipe movement. Some level of sticking occurs routinely in drilling operations and differential-pressure-pipe-sticking problems may not be totally prevented. These events only became problematic if the force required to pull the pipe free exceeds the strength of the pipe. Differential-pressure pipe sticking occurrence can be mitigated if some precautions are taken such as: maintaining the lowest level of fluid loss, the lowest level of drilled solids in the drilling fluid, and drill string rotation at all times, if possible as well as using the lowest differential pressure and selecting a drilling fluid that will yield smooth filter cake with low coefficient of friction. If sticking does occur, several methods can be used for freeing the stuck pipe but the most common approach is to place a small volume of oil, or special spotting fluid in a wellbore annulus to free differentially stuck pipe. Spotting fluids are designed to free differentially stuck drill strings by dehydrating or breaking up the filter cake, allowing penetration of the spotting fluid and wetting of the drill string. It reduces the stuck area and the forces of cohesion between the pipe and cake, and allowing pipe to be pulled free. Differential sticking tendency of different drilling fluids were determined in laboratory using sticking tester as well as influence of spotting fluids on freeing differentially stuck pipe. Results of the testing are presented in the paper.

Stuck Pipe; Differential Sticking; Spotting Fluids

nije evidentirano