Mud logging
This provides well owners and producers with information about the lithology and fluid content of the borehole while drilling.
Mud logging technicians in an oil field drilling operation determine positions of hydrocarbons with respect to depth, identify downhole lithology, monitor natural gas entering the drilling mud stream, and draw well logs for use by oil company geologist.
The mud logging company is contracted specifically as to when to start well-logging activity and what services to provide.
Mud logging may begin on the first day of drilling, known as the "spud in" date, but is more likely at some later time (and depth) determined by the oil industry geologist's research.
This information (known as "offset data") can provide valuable clues as to the characteristics of the particular geostrata that the rig crew is about to drill through.
Most of the data logged by an MWD technician comes from expensive and complex, sometimes electronic, tools that are downhole installed at or near the drill bit.
Other real-time drilling parameters that may be compiled include, but are not limited to; rate of penetration (ROP) of the bit (sometimes called the drill rate), pump rate (quantity of fluid being pumped), pump pressure, weight on bit, drill string weight, rotary speed, rotary torque, RPM (Revolutions per minute), SPM (Strokes per minute) mud volumes, mud weight and mud viscosity.
Thus both visual evidence of spalling and mathematical plotting assist in formulating recommendations for optimum drilling mud densities for both safety (blowout prevention) and economics.
Sample of drill cuttings of shale while drilling an oil well in Louisiana . For reference, the sand grain and red shale are approximately 2 mm in diameter.