Reduced Polymer Loaded Fracturing Fluid For Extreme Temperature Proppant Fracturing

Abstract

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 high pH that leaves insoluble residue and tendency to form scales with divalent ions. In this paper, newly developed reduced polymer loaded fracturing fluids based acrylamide polymer was deployed from lab developments to field implementation. A thermally stable acrylamide-based polymer with a reduced polymer loading of 30-40% less than guar-based fracturing fluid was considered to minimize formation damage concerns. The crosslinked fracturing fluid viscosity was optimized at 340°F, bottomhole static temperature, and 315, 290, 265 and 240°F cooldown temperatures using a high pressure high temperature (HPHT) rheometer. For successful field deployment, a novel reduced polymer fracturing fluid was evaluated in the following sequence: chemical management, quality control, optimization of fracturing fluid formulations with field water, field mixing procedure, on-site QA/QC, data frac analysis and execution of main treatment. This paper presents rheological studies of reduced polymer loaded fracturing fluids at bottom hole static temperature (BHST) and cool down temperatures of selected well candidates that demonstrate the superior thermal stability of this novel fracturing fluid. With a polymer loading of 35 lb/1000 gal, the fluid viscosity stayed above 300 cP at 100 1/s shear rate for 60 min at 340°F. The fracturing fluid formulations were optimized using both live and encapsulated breakers using high pressure and high temperature rheometer. Due to the fast hydration of the base polymer, the linear gel was mixed on-the-flying during the main fracturing treatment. The main fracturing treatment was successfully executed with a 40 barrels per minute (bbl/min) pumping rate with increased proppant concentration up to 4.5 pounds per gallon (ppa) using 40/70 HSP (high strength proppant) 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 lessons learnt during novel fracturing fluid deployment.