Schlumberger

Technical Paper: The Evolution of Hole Opening while Drilling Practices to Enlarge Salt and Subsalt Sections in the Gulf of Mexico

Society: AADE
Paper Number: 09-ntce-09-02
Presentation Date: 2009
 

Abstract

The North American gulf coast offshore continental basin was formed in late-middle to early-upper Jurassic geologic period and contains the largest known deposits of salt in the world. The salt encountered in this region is relatively soft, with very low permeability and porosity, and has the ability to deform under temperature and pressure. Deepwater drilling in the Gulf of Mexico (GoM) means drilling salt and subsalt sediments. Drilling salt in different regions requires different drilling practices and challenges. For instance, most of the salt and subsalt sections in the GoM involve hole opening devices while drilling for a variety of reasons, such as equivalent circulation density (ECD) management, reduction of salt creep to ensure casing to bottom, reduction of cementing pressures, etc.

The petroleum industry is continually pushing to drill longer, faster, and safer sections; salt and subsalt drilling is no exception to this philosophy. Holes have been enlarged with concentric underreamers in many wells in the GoM. However, over 20% of all the underreaming runs evaluated between 2004 and 2005 had a possible negative impact on bottomhole assembly (BHA) performance from inadequate enlarging or underreaming practices.

This paper summarizes the analysis of the evolution of different practices for hole-opening devices while drilling in the North American GoM and recommends a set of practices that has proven successful during drilling to yield optimal salt and subsalt drilling performance.