Mineral oil-based drilling muds are toxic, not readilybiodegradable and thus have cumulative impact on terrestrial,coastal and marine habitats. The base fluid for mineral oil-basedmud development has limited source of supply.Vegetable oils are renewable, highly biodegradable, can beproduced as per industry demand and thus could be a suitablecandidate for development of a highly biodegradable oil-basedmud with a sustainable source of supply. They have higherflash and fire points, better thermal stability, no detrimentalimpact on the surrounding environment and are much lesshazardous compared to mineral oils. Due to biodegradablenature of vegetable oils, drill cuttings will have noenvironmental impact if the cuttings are disposed directly to thesurrounding environments. Due to non-reactive nature ofvegetable oils with clays and shales, their technicalperformance in maintaining borehole stability is comparable tomineral oil. On the other hand, due to readily biodegradablenature and negligible toxicity effect, vegetable oil-based mudperformance should be comparable to water-based mud fromenvironmental point of view. Hence, vegetable oil-based mudcould be a potential solution to meet the current as well asfuture technical and environmental challenges.An invert emulsion mud was developed using a blend ofvegetable oil to study the rheological and filtration propertiesand evaluate its suitability for oil well drilling. Initial mudformulation indicates that development of a viable OBM is notpossible using the conventional approach due to the highinherent viscosity of vegetable oils and significant thermaldegradation at high temperature. However, processing andtreatment of vegetable oils lead to the formulation of avegetable oil-based mud with desirable rheological propertiesand excellent thermal stability. Preliminary test results indicatethat the processed vegetable oil-based mud produces suitablelow end rheological properties including gelling characteristics.Thermal conditioning of the mud at 150 °C for 16 hours indicates no significant changes in the rheological properties ofthe mud. The high thermal characteristics of vegetable oilsindicate their safe operation for all practical range oftemperatures.
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