Changes

==Mud logging data==

==Mud logging data==

The mud loggers on the rig site will monitor the drilling parameters during the well operation, and these are summarized graphically as a mud log. The mud log will include a lithology log. This is a depth plot showing in graphical form the percentage of the various lithologies in each cutting sample recovered while drilling the wellbore. A written description will be made for the lithology of the drill cuttings. Accompanying the lithology log is a record of the rate of penetration of the drill bit. This is an indication of lithology; sandstone is normally drilled faster than shale for instance. Any drilling problems encountered or changes in the drilling parameters will be reported in the margins of the mud log. The presence of oil shows will be noted. The gas returns and gas chromatography analysis are monitored and graphed against depth. High gas returns are a sign that a hydrocarbon reservoir may have been drilled. Significant concentrations of the higher alkanes on the gas chromatograph can indicate that an oil zone has been penetrated. The mud log is used as a first pass, qualitative indication of reservoir presence and quality. A more detailed and accurate representation will be available once wireline logs have been run and interpreted.

The mud loggers on the rig site will monitor the drilling parameters during the well operation, and these are summarized graphically as a mud log. The mud log will include a lithology log. This is a depth plot showing in graphical form the percentage of the various lithologies in each cutting sample recovered while drilling the wellbore. A written description will be made for the lithology of the drill cuttings. Accompanying the lithology log is a record of the rate of penetration of the drill bit. This is an indication of lithology; sandstone is normally drilled faster than shale for instance. Any drilling problems encountered or changes in the drilling parameters will be reported in the margins of the mud log. The presence of oil shows will be noted. The gas returns and [[gas chromatography]] analysis are monitored and graphed against depth. High gas returns are a sign that a hydrocarbon reservoir may have been drilled. Significant concentrations of the higher alkanes on the gas chromatograph can indicate that an oil zone has been penetrated. The mud log is used as a first pass, qualitative indication of reservoir presence and quality. A more detailed and accurate representation will be available once wireline logs have been run and interpreted.

The mud loggers also collect bags of rock cutting samples at regular intervals while the well is being drilled. These may be used later for biostratigraphic and lithological analysis.<ref name=Whittaker_1992>Whittaker, A., 1992, [[Mudlogging: the mudlog|Mudlogging: The mudlog]], in D. Morton-Thompson and A. M. Woods, eds., [http://archives.datapages.com/data/alt-browse/aapg-special-volumes/me10.htm Development geology reference manual]: AAPG Methods in Exploration Series 10, p. 101–103.</ref>

The mud loggers also collect bags of rock cutting samples at regular intervals while the well is being drilled. These may be used later for biostratigraphic and lithological analysis.<ref name=Whittaker_1992>Whittaker, A., 1992, [[Mudlogging: the mudlog|Mudlogging: The mudlog]], in D. Morton-Thompson and A. M. Woods, eds., [http://archives.datapages.com/data/alt-browse/aapg-special-volumes/me10.htm Development geology reference manual]: AAPG Methods in Exploration Series 10, p. 101–103.</ref>