Gas production from the Strawn Limestone formation in Crockett County, Texas is generally only commercial after stimulation. Historically, the most successful stimulation treatments typically consist of large acid fracturing treatments. Several techniques have been used, including gelled acid, gelled water pads and gelled acid pumped in alternating stages and crosslinked acid systems.
Gelling of acids has been accomplished for years using emulsions to facilitate the addition of polymer to acid to achieve good hydration. Recently, a new emulsion system and polymer were introduced into this area which significantly improved efficiency both in developing fluid properties and operations on location. The micelles of this new polymer emulsion are approximately 1/15th the size of those previously applied. The polymer emulsion uses a highly specific external activator to initiate and promote hydration, dramatically reducing the formation of "fisheyes". In addition, it allows for continuous mix operations on location.
Production results are presented from three wells, showing a 34% improvement in production in which the new polymer system has been used. In addition, production responses to several different treatments are compared, which show crosslinked acid fracture treatments to be the most successful. Treatment details along with a description of the new emulsion chemistry and operational advantages are presented.