Guar gum and its derivatives based fracturing fluids are most commonly used in hydraulic fracturing. For high temperature wells, guar-based fracturing fluids need to be formulated with higher polymer loading and at a high pH that leaves insoluble residue and tendency to form scales with divalent ions. In this paper, a systematic approach to field deploy a novel low-polymer loading, nondamaging acrylamide basedfracturing fluid system is presented.
Thermally stable acrylamide-based polymer with reduced polymer loading of 30-40% less than guar-based fracturing fluid was considered to minimize formation damage concerns. For successful field deployment, a novel nondamaging fracturing fluid was evaluated in following sequence: chemical management and quality control, optimization of fracturing fluid formulations with field water, field mixing procedure, onsite QA/QC, friction analysis, leakoff analysis, data frac analysis and execution of main fracturing treatment. In both scenarios, batch mixing and on-the-fly mixing of linear gel were evaluated. The friction of crosslinked fluid was analyzed by using bottomhole gauge and fluid efficiency was evaluated during data frac analysis.
This paper presents rheological studies at bottomhole static temperature (BHST) and cool down temperatures of selected well candidates that demonstrate superior thermal stability of this novel fracturing fluid. With polymer loading of 25 lb/1000 gal, the fluid viscosity stayed above 300 cP at 100 1/s shear rate for 2 hours at 290°F. The fracturing fluid formulations were optimized using both live and encapsulated breakers with high pressure and high temperature (HPHT) rheometer. Due to the fast hydration of the base polymer, the linear gel was mixed both in batches and on-the-flying during the main fracturing treatment. Slightly higher friction at higher pumping rate was observed by the down hole gauge during data frac for this novel fracturing fluid as compared to guar-based fracturing fluid. The main fracturing treatment was successfully executed with 45-50 barrels per minute (bbl/min) pumping rate with increased proppant concentration up to 5 pounds per gallon (ppa) using 30/50 high strength proppant (HSP) proppant.
The fracturing fluid system based on the novel acrylamide copolymer offers advantages over guar-based fracturing fluid such as low polymer loading, excellent high temperature stability and less formation damage. This paper presents a systematic approach and lesson learnt during novel fracturing fluid deployment.