ABSTRACT
An alternative system to conventional HEC (hydroxyethylcellulose) and particulate fluid loss materials has been developed for fluid loss control in high permeability Gulf of Mexico Flexure trend completions. In offshore operations, the problem of controlling fluid loss to the formation is critical in achieving successful gravel pack completions. The problem is magnified in this environment because of the use of expensive high density brine, lost rig time, and increased standards for well control and safety. A newly developed fluid loss system which consists of a crosslinkable, derivatized HEC incorporating a branched functional group oh an HEC backbone has been evolving in the industry. The functional group provides a nonionic reaction site which allows the polymer to be crosslinked at a low pH, and broken in a controlled manner using a newly developed breaker.
Other fluid loss control systems used in Flexure trend completions exhibit specific problems which can be attributed to (1) physical properties of the particular material, and (2) the method of application. For instance, in many high permeability wells, noncrosslinkable HEC pills have proven inadequate for controlling fluid loss to an acceptable level, and in some cases have allowed significant invasion of HEC, thus potentially resulting in permeability impairment. Particulate fluid loss materials present other problems in that they can be difficult to remove from perforations.
Laboratory and field tests demonstrate efficient fluid loss control and potential for reduced formation damage with this new crosslinkable HEC (CLHEC). Internally broken crosslinked gel has shown more favorable return permeability in core tests than regular HEC polymer commonly used in the industry. The CLHEC system deposits a thin, crosslinked polymer filter cake which helps prevent fluid loss, but which can be removed by means of an internal breaker, an acid wash, or both. Subject paper presents laboratory and field data illustrating properties of the new fluid loss control system in high density brine applications.