Editing Formation evaluation (section)

===Mud logging===

Mud logging (or Wellsite Geology) is a [[well logging]] process in which [[drilling mud]] and drill bit cuttings from the formation are evaluated during drilling and their properties recorded on a strip chart as a visual analytical tool and stratigraphic cross sectional representation of the well. The [[drilling mud]] which is analyzed for [[hydrocarbon]] gases, by use of a [[gas chromatograph]], contains drill bit cuttings which are visually evaluated by a mudlogger and then described in the mud log. The total gas, chromatograph record, lithological sample, pore pressure, shale density, D-exponent, etc. (all lagged parameters because they are circulated up to the surface from the bit) are plotted along with surface parameters such as rate of penetration (ROP), Weight On Bit (WOB), rotation per minute etc. on the mudlog which serve as a tool for the [[mudlogger]], drilling engineers, [[mud engineer]]s, and other service personnel charged with drilling and producing the well.