Foamed cement job successful in deep HTHP offshore well

Abstract

A foamed cement slurry successfully isolated problem formations behind a liner in a high-temperature/high-pressure (HTHP) well in Mobile Bay. The foamed cement slurry, with an average density of 11.8 ppg, was used to cement about 10,000 ft of a 9 5/8 inch. liner. Foamed cement has classically been considered when light-weight slurries are required. In this application, the use of foamed cement was not for its light-weight properties but rather for its unique performance in high-stress environments. Both offshore and zero-discharge requirements had to be met, and special considerations for each were addressed in this operation. Previous research has shown benefits of compressible slurries in preventing flow after cementing. The study was geared toward gas flow rather than fluid flow, but additional work indicates that foamed cement can be effective in preventing both gas and fluid migration. Based in part on this work and the study on temperature-induced stress failure of cement, a foamed slurry appeared to be an appropriate choice. In an attempt to address these problems, a 15.0-ppg Class H cement system foamed with nitrogen was used on this liner job. Because of the high temperatures in this well, the slurry was stabilized with 35% silica fluor. Othermore » additives for retardation, foaming agent, and foam stabilizers were added as liquids. This paper reviews the performance and handling procedures of this cementing operation.« less