IMPROVING THE RHEOLOGICAL AND FILTRATION PROPERTIES OF OIL-BASED DRILLING FLUID WITH MATE/BA/MA COPOLYMER

The high pressure and high temperature conditions encountered during drilling of deep wells pose a significant challenge to control filtration and maintain optimum drilling fluid rheology. However, most commercial oil base drilling fluid systems have limitations such as reduced rheology and filtration control if the fluid is exposed to temperatures higher than 150 degrees C for prolonged periods of time. In this study, copolymer based on monomer of methacrylic acid, tetradecyl ester (MATE), butyl acrylate (BA) and methylmethyacrylate (MA) was synthesized with suspension polymerization. The copolymer was characterized with Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM). The white oil adsorption capacity from room temperature to 120 degrees C was evaluated. The effect of the copolymer on the rheology and filtration properties of oil-based drilling fluid (OBDF) was investigated. The results indicated that the copolymer has near spherical and porous structure, capable of absorbing large amount of oil. It could reduce both the API fluid loss and HTI-IP fluid loss after hot rolling at 200 degrees C for 16 hours, and increase the viscosity of the fluid after hot rolling at 180 degrees C for 16 hours. The copolymer showed superior performance than conventional modified lignite and modified asphalt product, and had a promising future of practical application.