New Salt-Tolerant Friction-Reducer System Enables 100% Reuse of Produced Water
Authors: Wilson Adam 
Published: November 2017

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 184052, “Case Study: A New Salt-Tolerant Friction-Reducer System Enables 100% Reuse of Produced Water in the Marcellus Shale,” by Liang Xu, SPE, Multi-Chem, a Halliburton Service; Paul Lord, Halliburton; Justin Koons and Todd Wauters, SPE, Multi-Chem, a Halliburton Service; and Sam Weiman, EQT, prepared for the 2016 SPE Eastern Regional Meeting, Canton, Ohio, USA, 13–15 September. The paper has not been peer reviewed.

To continue to treat multiple clusters in longer laterals effectively, even for stages near the toe, a robust friction-reducer (FR) system typically is required to overcome pipe friction. Additionally, using a single FR system throughout the entire treatment that can tolerate various water sources of varying salinity up to 300,000 ppm is imperative. This paper discusses the field trials of a new salt-tolerant FR system in the Marcellus Shale.

Introduction

FRs are used to enable high-rate pumping of water while maintaining lower treating pressures in both slick water fracturing and coiled-tubing stimulation applications. Typically, the performance of conventional acrylamide/acrylic acid copolymer or partially hydrolyzed polyacrylamide-based FRs diminishes as the dissolved-ion content of the source water increases and can be dependent on both the type and the concentration of ions present in the source water. Because of this limitation, flow-back and produced water used for slick-water applications are often diluted with a freshwater source to maintain adequate friction-reducing performance. To enable the use of 100% produced water, new friction reducers have been developed that are capable of providing near-freshwater performance in flowback and produced water exceeding 300,000 ppm total dissolved solids (TDS).

The new salt-tolerant FR consists of FR systems that are designed to work in a specific range of high salinity to enable the use of 100% flowback and produced water in slickwater hydraulic- fracturing applications without requiring dilution with fresh water. The salt-tolerant FR service can handle TDS levels greater than 300,000 ppm; is effective in water containing a variety of dissolved salt ions, including chlorides, sulfates, sodium, calcium, and magnesium; and can tolerate a variety of unknown contaminants that might render conventional FRs ineffective. The new FR system is effective at low concentrations (0.25 to 1 gal/1,000 gal) in clay-control brines and flowback and produced-water sources.

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 of polymer to 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.