Publication Details (including relevant citation information):
Schultheiss, Nathan, Fontenelle, Lucas, Welton, Thomas -
Abstract: Abstract Currently, guar-based fluid systems are the preferred choice for hydraulic fracturing operations, primarily because the fluid formulations can be widely varied depending on reservoir conditions and operational needs. However, fluids prepared with guar are inherently dirty and contain water-insoluble residues, which can significantly reduce the permeability of the proppant pack when flowing back and producing the well. This can result in a possible reduction in overall hydrocarbon production. Herein, a new, residue-free, hydraulic fracturing fluid system has been developed that provides excellent performance during the fracturing process and includes superior cleanup characteristics. The "res-free?? fluid is a premium fracturing fluid with comparable, or improved, properties compared to a typical guar/borate crosslinked system. First, because the fluid does not generate insoluble residue on breaking, excellent regained conductivity and core permeability can be achieved, which has been demonstrated both in laboratory testing and in the field by measuring well productivity. Second, the fluid is robust, allowing for precise viscosity and breaker control. Third, the fluid is salt tolerant and is usable up to temperatures of 275 F. Finally, it is capable of providing excellent proppant-carrying characteristics. The proppant-transport characteristics of this fluid are comparable to other fluids in use, as measured by a slurry viscometer. This paper highlights regained conductivity and core permeability, rheological performance, and proppant-transport characteristics of the new fluid and provides comparative guar-based fluid data. This new, residue-free fluid is applicable to fracturing a wide variety of reservoirs, including unconventional reservoirs, and has been used successfully in over 180 wells (>2,250 stages/zones) at temperatures up to 300 F bottomhole static temperature (BHST). Future papers will present case studies of jobs and will provide production and well performance results. Introduction Water viscosifying agents, such as guar and its derivatives, have been relied on within the oil and gas industry for many years (Beckwith 2012). These polymers provide viscosity, which supports and carries proppant as well as creates fracture length/width during the hydraulic fracturing process. To accomplish this function, the fluid viscosity is increased exponentially to a value that has been determined to be required for efficient transport of proppant into the hydraulically generated fractures. Furthermore, the fluid also provides fluid-loss and leakoff control. Once the fracturing treatment is complete, reducing the viscosity of the fluid is essential for promoting the flowback of the fracturing fluid so that minimal obstruction occurs as the hydrocarbons move from the formation to the wellbore. Additionally, on breaking the fluid, obtaining the highest degree of proppant pack conductivity and permeability ensures that maximum return will be achieved once the well is placed on production. It is widely accepted that reducing gel damage to the proppant pack and formation leads to minimal flow restrictions, which directly impacts the return of oil and gas to the wellbore (Almond 1984). Thus, reducing insoluble residue within the proppant pack can be advantageous, whether from the gel breaking or from the polymer manufacturing process.