A new hydraulic fracturing fluid has been developed that is capable of stimulating high pressure/high temperature (HPHT) wells at 450°F without the need for cooling preflushes. Good viscosity at fluid temperatures as high as 450°F gives the synthetic fluid the potential to provide substantially better proppant placement than polysaccharide-derivative gels. The gelling agent is based on a terpolymer of 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, and acrylic acid that can be crosslinked with zirconium. The crosslink onset temperature can be varied over the range of 100 to 280°F, allowing optimization for particular well conditions. A delayed acting oxidizing breaker can be added to accelerate the gel's degradation, allowing rapid flowback and early production. The gelling agent is provided to the wellsite as a liquid-gel concentrate that is designed to be mixed and pumped with conventional fracturing equipment and procedures.
This paper discusses the laboratory testing, treatment design, and job execution leading to the successful hydraulic fracturing of two South Texas gas wells at depths of 23,300 and 18,900 ft with bottomhole static temperatures of 450°F and 433°F, respectively. The jobs were pumped as designed, with 190,000 lbs. of high-strength, resin-coated proppant placed in each zone at concentrations up to 9 lb/gal. Average treating pressures were 13,100 and 11,250 psi with slurry rates of 21 and 25.7 bbl/min, respectively. Cleanup was rapid, with gas flowing to the sales line the day after the treatment at a rate in excess of 4,000 MCF/D; in the case of the second well.