Mud logging is the creation of a detailed record (well log) of a borehole by examining the cuttings of rock brought to the surface by the circulating drilling medium (most commonly drilling mud). Mud logging is usually performed by a third-party mud logging company.
In the context of oil and gas exploration, mud logging serves as a means to document the subsurface geology of a borehole, using samples of rock retrieved from the drilling fluid. This process is often conducted by a third-party company with expertise in geological analysis.