The disclosure relates to drilling fluid compositions, and their method of use, comprising a C16 unbranched internal olefin, including blends of the C16 unbranched internal olefin and a C16 linear alpha olefin. The exemplary drilling fluids are characterized by properties, e.g., pour points and kinematic viscosities, that enable them to be particularly useful in deep water drilling operations and have reduced environmental impact, e.g., increased biodegradation and reduced sediment toxicity.