Smart Drilling Fluids Formulations for Sensitive Shale Formations Using Surfactants and Nanoparticles

Abstract

Abstract The demand for oil and gas is continuing to rise with a growing population and worldwide industrialization. Surfactants are considered excellent additives for drilling formulations because of their unique properties and chemical structure. The surface-modified nanoparticles in the drilling fluids (DFs) help to improve the rheological and filtration properties of water-sensitive shale formations. The water-sensitive shale formations in the wellbore often result in swelling after interacting with water-based DFs. The swelling of shale formation impacts the rheological and filtration properties of DFs. The aim of this study is to formulate DFs with cationic surfactants and surface-modified nanoparticles to minimize shale swelling and improve the rheological and filtration properties. Various drilling fluid formulations were prepared with bentonite as a basic constituent of DFs while Gemini surfactant and graphene nanoparticles were added with concentrations of 0.5%. The rheological and filtration properties were determined at room temperature. The shale inhibition tests were performed to analyze the swelling inhibition properties of DFs. The surface-modified nanoparticles along with the cationic surfactant make a stable dispersion of DFs. The presence of nanoparticles in the DFs enhances the rheological and filtration properties. The filtrate loss has been significantly reduced by incorporating graphene nanoparticles and Gemini surfactant-modified graphene nanoparticles. The rheological properties such as plastic viscosity, yield stress, and gel strengths have been improved by the combined addition of surfactant-modified nanoparticles. The reduction of filtrate loss was due to the clogging effect of small passages in the filter cake while long alkyl chains of surfactant molecules spread over the filter cake making a hydrophobic film that minimizes the contact of water with the filter cake. Moreover, the swelling inhibition test such as the linear swelling test showed that the presence of nanoparticles and cationic surfactants significantly enhanced the shale swelling inhibition and reduced the percentage of swelling compared to the DI water. The cationic surfactant interacts with the negatively charged clay particles through electrostatic forces and surfactant along alkyl chains wraps around the clay particles which leads to the minimum swelling of shale formations. This study reveals that the formulations based on surface-modified nanoparticles and surfactants in water-based DFs can inhibit shale swelling and improves the borehole stability for water-sensitive shale formations.