Scale Mitigation Strategy for Fracturing Using Seawater-Based Fluid

Abstract As part of the continuous efforts to save freshwater resources in the Middle East, seawater-based fracturing fluid offers a high-potential solution to help save millions of gallons of fresh water while developing fracturing fluids for hydraulic fracturing applications. Scale deposition is one of the major technical challenges for fracture stimulations using seawater-based fluid. To understand the scale deposition and mitigation for fracturing using seawater-based fluid, a series of dynamic and static performance, compatibility, and thermal stability tests were conducted. Results showed that harsh scale forms with mixing raw seawater and high total dissolved solids (TDS) tested formation water at higher temperatures under dynamic and static conditions. Scale inhibitors cannot effectively inhibit scale deposition in such harsh scaling conditions because of the issues of compatibility and performance at static conditions. Nanofiltration of seawater is introduced to remove most of the sulfate ions in seawater and help significantly reduce the scaling tendency when mixing with high TDS formation water during fracturing treatments using seawater-based fluid. Combining the nanofiltration technique and scale inhibitor application, the scale issue during fracturing using seawater-based fluid can be effectively mitigated and was determined to be suitable for field application. The scale inhibitor showed good compatibility with nanofiltered seawater. The dynamic scaling tests were successful when the proper scale inhibitor and optimum concentration were used, while the static tests did not form any precipitation. Thermal aging resulted in a color change for all tests, as expected, and the performance of the thermal-aged scale inhibitor was evaluated. This paper provides insight into the scale deposition and inhibition for fracturing treatments using seawater-based fluid at high-temperatures up to 300°F and furthers the effective strategies to address the scale issue during fracturing using seawater-based fluid.