mud logging

mud logging, mud coring [Mud logging is a geological and engineering procedure designed to provide well operators with information concerning the identification and evaluation of potential hydrocarbon-bearing formations without interrupting routine drilling. It is a procedure designed to measure various chemical and mechanical parameters of drilling fluid (mud) and well-cuttings (formation rock chips) as well as to provide a reliable time log of drilled formations. During drilling, the volume of rock excavated by the bit is transported to the surface through the annular section of the hole by the drilling fluid. As the cuttings rise, hydrostatic pressure exerted by the mud column decreases, thus allowing hydrocarbons (gas and/or oil) contained in the pore space of the cuttings to expand and become entrained in the drilling fluid; some portion of the hydrocarbons remains in the cutting fragments. At the surface, cuttings and gas are mechanically separated from the mud stream and...