High Density Fracturing Fluid: Offshore Completion of Ultra-High-Pressure Wells

Abstract Development in offshore high-pressure wells led to the need of new technologies to manage the challenging pressure conditions during stimulation operations. This is an introduction to a new high density fracturing fluid for wells that have very high formation pressure resulting in surface treating pressure to be as high as 20,000 psi. The goal of developing this high-density brine fracturing fluid was to obtain a consistent, reproducible fluid that will maintain the surface treating pressure below 15,000 psi allowing the use of industry standard surface treating equipment. Using this system, a high pressure well with a bottom pressure of above 25,500 psi was completed. Thorough laboratory testing was performed and included rheology, oil and grease, static sheen, and compatibility testing with completion brine and crude oil. Fracturing fluid composition was optimized to maintain a stable viscosity at 230°F for 150 minutes, and included a 20 minutes initial shear to simulate the fluid traveling from the stimulation vessel blender to the crossover port in the multizone tool. The fluid temperature was then increased to 255°F and had to maintain a minimum viscosity of 200 cP for 1 API shear after the temperature ramp. The job was then designed and completed as a frac-pack, with six stimulated zones in a single trip. A consistent high density and high viscosity fluid was successfully developed. This fluid used a 12.5 ppg sodium bromide base brine and maintained a viscosity of 800 cP for 150 min at 230°F and 200 cP for 1 sweep when the fluid temperature was ramped up to 255°F. This fluid was compatible with the well crude oil as well as packer and completion brine. This fluid was then applied in a six zone frac pack completion, which used a single trip multizone tool system, with a designed volume of 31,500 barrels (bbl) of base brine, and 3 million pounds of high strength ceramic proppant. Due to the volumes of fluid needed, between zones, fluid had to be transferred over water between offshore supply, and the stimulation vessels. The fluid showed consistent rheology after every transfer. Furthermore, the fluid maintained the surface treating pressure below 12,000 psi. This well was completed successfully, with no issue.