Performance of a water-based drilling fluid is determined by the physical and chemical properties of the fluid such as viscosity, gel strength, fluid density, and filtration (or fluid loss) properties. A good drilling fluid should have satisfactory fluid loss value and be able to deposit a thin, low permeability filter cake on the wall of the borehole for consolidation of formation and prevent fluid passage into the formation. Filtration control of water-based fluid systems is necessary to prevent drilling problems such as excessive torque and drag, differential pressure sticking, borehole instability and formation damage.<br/><br/>Clays such as bentonite are naturally occurring and are commonly used as a filtration control additives in drilling fluids. Other cost-effective fluid loss control additives include natural occurring polymers such as starch, cellulose, and lignite. The use of thermally stable polyacrylates and polyacrylamides as synthetic fluid loss control additives in drilling fluids is later introduced. The three generations of materials – natural clays, natural polymers, and synthetic polymers – all capable of providing micron scale plugging on filter cakes. However, this means that nanopores on filter cakes will still be able to accommodate fluid loss into the formation. This led to the development of organic and inorganic nanoparticles (i.e. silica nanoparticles, iron oxide nanoparticles and graphene) that can plug nanometer sized pores to prevent water loss and play a significant role in developing compacted and impermeable filter cakes. However, nanoparticles are chemically sensitive to downhole changes and undergo agglomeration, and they have poor dispersion leading to particle instability.<br/><br/>In this presentation, a novel star polymer that is designed to overcome the limitations of current nanoparticle technology will be presented. The self-assembling property of the designed star polymer helps to fill micro- and nano-cavities in filter cakes which provide significant reduction in fluid loss when compared to commercial additives.

Self-assembling nanoparticle sealants for filtration control in water-based fluids

ACS Fall 2021

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