Drilling fluids are essential for oil and gas exploration. Two key drilling fluid functions include sediment suspension and the formation of filter cake. Filter cake is an ideally thin, impermeable layer which isolates drilling fluid and stabilizes the wellbore. Common drilling fluids are oil and synthetic-based, which perform well but suffer from high cost, environmental damage, health hazards, and disposal problems. Water-based drilling fluids (WDFs) are cheaper and less hazardous, but have poor filtration properties due to their inherent water content. WDFs form a filter cake through the action of bentonite clay (BT). BT is a sheet-like particle with a pH-dependent edge charge and a permanent negative surface charge. These charges result in interactions of BT particles which aid in sediment suspension. Unfortunately, significant improvements in sediment suspension require high amounts of BT solids, resulting in a thicker, more permeable filter cake. Herein lies the problem; low-solid BT-WDFs have limited sediment suspension capability, whereas high-solid BT-WDFs cause fluid loss. Furthermore, salt rich environments result in the transport of charged ions into the BT-WDF, interfering with the layered BT structure and resulting in further fluid losses. Inorganic nanomaterials such as carbon nanotubes have been tested as additives in WDFs. However, inorganic materials are typically insoluble, non biodegradable, and can pose health risks. Cellulose nanocrystals (CNCs) are a safe and renewable biopolymer that, even at low concentrations, greatly support the rheological properties of BT-WDFs. This research explored CNC-polymer hybrids which reduced the effect of salt on BT-WDFs. The CNC hybrids were created using different grafting-from techniques to covalently attach polystyrene sulfonate, polyacrylamide, and a copolymer of the two onto the CNC surface. WDF efficacy was tested using a filter press. The industry standard press is large and time consuming to operate, so a novel miniature press was created. The results were qualitatively compared with the industry standard press to determine their validity.

Quick evaluation of grafting-from techniques to synthesize salt resistant CNC-polymer hybrids as additives in water based drilling fluids using a scaled-down fluid retention testing device

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.