Friction reducers (FRs) are an important component for slickwater hydraulic fracturing applications. To continue to effectively treat multiple clusters in longer laterals, even for stages out near the toe area, a robust FR system is typically required to overcome pipe friction. Additionally, it is imperative to be able to use one single FR system throughout the entire treatment that can tolerate various water sources of varying salinity up to 300,000 ppm. This paper discusses the field trials of a new salt-tolerant FR system in the Marcellus shale.
A three-well trial program was initiated in the Marcellus. Various water sources with varying salinities were used with up to 100% re-use of produced water. The operator had not been able to keep the surface treating pressure between 8,000 and 8,500 psi using a standard anionic FR, which typically resulted in a lower pumping rate of less than 100 bbl/min; the first few stages using the standard FR in these wells indicated this was the case. After switching to the new FR, however, the pumping pressure immediately dropped to below 8,500 psi and the pumping rates were increased and maintained at 100 bbl/min.
This new salt-tolerant FR system consists of a water-in-oil cationic polymer and an inverter. Unlike other FRs, the distinctive advantage of the new FR is that the ratio between polymer and inverter can be readily adjusted on the fly to achieve maximum friction reduction. During the pumping operations, it was demonstrated that the inverter was sufficiently quick to invert and release the polymer from oil to water, and the cationic polymer was extremely efficient at reducing additional pipe friction, even with severely impaired water. Additionally, the use of a single FR reduces inventory stock and simplifies on location quality assurance of material usage.