borevæsker

Borevæsker, or drilling fluids, are liquids used in the drilling of boreholes to facilitate operations, stabilize the wellbore, transport drill cuttings to the surface, control formation pressures, and cool and lubricate the drill bit. They also help seal the wellbore against influxes of formation fluids and minimize formation damage.

There are several main types of borevæsker. Water-based muds (WBMs) use water as the base fluid and are common in onshore drilling. Oil-based muds (OBMs) use mineral or synthetic oils and are favored for reactive shales and high-temperature environments. Synthetic-based muds (SBMs) use synthetic esters or olefins as the base fluid and aim to combine performance with environmental advantages. In some operations, foams or gas-enhanced fluids are used, especially for lightweight or underbalanced drilling.

A borevæske consists of a base fluid plus additives. Weighting agents such as barite increase density to counterbalance formation pressures. Viscosifying agents and thinners control rheology, which governs the mud’s flow and carrying capacity for cuttings. Filtration-control agents reduce fluid loss into the formation. Shale inhibitors, lubricants, anti-corrosion additives, and biocides protect equipment and the wellbore. The composition is tailored to the geology, well depth, and environmental requirements.

Key properties include density (pressure control), viscosity and gel strength (carrying capacity), filtration rate and mud cake quality, pH, and solids content. Mud systems are managed by mud engineers through circulation, sampling, and testing to maintain target properties. Solids-control equipment, pit design, and waste handling are important for environmental compliance.

Borevæsker choices balance operational performance, well integrity, cost, and environmental impact, with WBMs typically cheaper and simpler to manage, OBMs offering superior performance in challenging formations, and SBMs aiming to reduce ecological footprint.