A Novel Seawater-Based Fracturing Fluid for Streamlined Logistics, Long-Term Scale Protection, and Enhanced Oil Recovery

Seawater-based fracturing fluid systems are well known for the economic and logistical benefits they provide, including unlocking a usable water source in locations that lack access to fresh water and eliminating the need for extra freshwater supply vessels at offshore wellsites. However, a common challenge with these systems is the formation of scale that results when the high content of sulfate in seawater contacts a barium-rich formation. Additional challenges include minimizing gel residue and mitigating water blockages that can negatively impact oil production after the fracturing treatment. To address these issues, a new seawater-based borate-crosslinked fracturing fluid, with integration of a phosphorus-free polymeric scale inhibitor (SI) and a flowback aid, was developed and evaluated for scale inhibition, oil displacement efficacy and rheological performance. The seawater-based fracturing fluid rheology and compatibility with a scale inhibitor at varying concentrations were studied in a rotational rheometer. Static bottle test was used to evaluate the long-term barite inhibition. Oil migration and displacement of the fracturing fluid through a column flow apparatus were investigated to demonstrate the synergistic effect of the scale inhibitor and surfactant on enhancing oil mobility through porous media. Addition of various concentrations of SI does not impair the fluid crosslinking, aging and breaking process, and provides effective scale inhibition over a six-month extended shut-in period. With respect to oil displacement, the frac fluids containing the scale inhibitor and surfactant at certain concentrations outperform the control samples without these additives or that only contained a single additive. It is shown that the seawater-based fracturing fluid has good stability under all shearing schedules and has quick shear recovery after exposure to high shear, indicating the fluid has excellent proppant carrying capacity. With integration of a polymeric scale inhibitor (SI) and a flowback aid, the seawater-based borate crosslinked fracturing fluid demonstrates reliable rheological performance, superior scale inhibition, and improved oil displacement with reduced water blockage due to the synergistic effect of combining these chemistries. The integrated fracturing fluid system designed for seawater operations not only provides a reliable fluid performance, long-term scale protection, and better oil recovery, but also significantly reduces logistical costs for offshore applications, especially for those requiring additional supply vessel support to transport frac fluid. All these aspects of the fluid system result in a reduced treatment cost, increased operational efficiency in time and process, reduced fluid waste, and lower CO2 emissions.