Avoiding Fatal Attractions: How to Prevent Production-Killing Interactions between Wet Sand and Stimulation Fluids
Authors: Kakadjian Sarkis , Kitchen Jarrett , Gebrekirstos Amanuel 
Published: January 2025

Improving output from unconventional oil and gas reserves requires the appropriate proppant and chemicals not only to facilitate fracture creation but also to reduce damage to both the proppant pack and the reservoir itself. The interactions between polyacrylamides (PAMs) used as friction reducers (FRs), additives, and p roppants are complex. Variations in water quality such as changes in pH levels and electrolyte concentrations can alter the relative charges of these components. These charge shifts can lead to phenomena like repulsion, absorption, or flocculation among the various components. This study aimed to develop strategies, either chemically or mechanically, to mitigate damage caused by clay, quartz, and feldspar suspensions resulting from interactions between wet sand sources and the fluid system. To achieve this goal, the research team first monitored the turbidity of supernatant samples as well as the conductivity of proppants from different sand mines. Fine adhesion to proppant surfaces was assessed and Zeta Potential measurements were conducted of fines suspended within the fluid system to evaluate flocculation potential. The effects of three PAM-based FRs were compared: a traditional anionic copolymer made from sodium acrylate and acrylamide; a cationic polyacrylamide based on acryloyloxy-ethyl-trimethyl-ammonium chloride (AETAC); and a terpolymer partially substituted with 2-acrylamido tert-butylsulfonic acid (ATBS). Also, the technical group teamed with a sand mine company in South Texas introducing changes on sequency of the sand cyclones during sand processing and following the outcome by turbidity measurements and analyzing the Quartz and Clay type per X-Ray Diffraction.

Testing was carried out across various water qualities. Findings indicated that particle bridging of fines by cationic polyme rs within the proppant pack is significantly more influenced by salinity than by anionic polymers. Furthermore, the strength of electrostatic charges on proppant/fines surfaces fluctuates with pH variations. The team evaluated the effect of additives such as surfactants, clay control agents, and biocides in the fracturing fluid on flocculation. Results showed that anionic PAMs performed better in lower-salinity brines containing total dissolved solids (TDS) below 15,000 parts per million (ppm). In contrast, at TDS levels exceeding 30,000 ppm, there were noticeable signs of increased flocculation among suspended particles in the supernatant. On the mechanical approach, processing all sand through twice number of Cyclones increased the levels of Quartz in the sand and decreased actual levels of Migrating Clays from approximately 3.5% to 1.3% also reflected in drop on the Turbidity levels by 90%. These results, combined with the actual conductivity data, is used to further enhance production, and expand the accessibility of local/lower-cost sand mines to reduce supply chain constraints by leveraging wet sand in hydraulic fracturing operation.