A Laboratory Study on the Use of Seawater in Crosslinked-Gels Used In Hydraulic Fracturing

As unconventional reservoirs continue to dominate the current economic climate, there is a great demand for developing innovative and efficient fracture treatment methodologies. Traditionally, the vast majority of hydraulic fracturing systems incorporate a freshwater-based fracturing fluid. However, freshwater is considered an expensive and valuable resource, particularly in the Middle East and for offshore completions. This research discusses the potential of seawater, a more cost-effective and accessible resource, as an acceptable replacement for current water sources. To develop a successful fracturing fluid system, the chemical composition of seawater, particularly the presence of high concentration cations and anions, must be considered. The primary purpose of this study is to understand how 1) changing temperature, 2) additive concentration, 3) water source, and 4) introducing an oxidizer breaker can affect the gel stability of two types of guar derivative gelling agents: hydroxyl propyl guar (HPG) and carboxymethyl hydroxypropyl guar gum (CMHPG), using High Temperature/High Pressure Chandler Rheometer. Arabian Gulf seawater was used to design and test a seawater-based fracturing fluid in the laboratory. To simulate fracking environments, a dynamic scale loop was used. The seawater sample and formation water mixture were mixed at a 50/50 ratio. Phosphonate type scale inhibitor was then tested at various concentrations, starting at 3,000 ppm, at a temperature range from 270 to 330ºF. Scale buildup is represented by a dramatic change in pressure. Results confirmed that seawater fluid stability at greater than 500 cP at a shear rate of 40 s^-1 for temperatures ranging from 270 to 330°F was feasible. The stability time varied with the given temperature constraint. Additionally, scale loop analysis depicts that scale can be mitigated at temperatures ranging from 270 to 330°F depending on the scale inhibitor concentration used. This work contributes to understanding how seawater based fracturing fluid can be formulated, and potential applications in hydraulic fracturing treatments. Maximizing the use of seawater could help rule out dependency on the scarce freshwater resources