Changes

In many wells, drill cuttings collected may represent the only subsurface data available for geological interpretation. After a detailed lithology description, cuttings are analyzed for hydrocarbon indications (see [[Mudlogging: Drill cuttings analysis]]). Traces of gas and oil in the cuttings represent formation hydrocarbons that have not been flushed by the [[drilling fluid]]. Gas in cuttings is analyzed by grinding a measured amount (approximately 100 mg) of unwashed cuttings in a blender, with any liberated gases analyzed by the standard gas detection system. This analysis is often divided into two components: total gas, comprising all combustible gasses; and petroleum vapors, comprising C2 through C5. This type of analysis can indicate the amount and composition of gases in the formation, even if the larger rock pores are flushed.

In many wells, drill cuttings collected may represent the only subsurface data available for geological interpretation. After a detailed lithology description, cuttings are analyzed for hydrocarbon indications (see [[Mudlogging: Drill cuttings analysis]]). Traces of gas and oil in the cuttings represent formation hydrocarbons that have not been flushed by the [[drilling fluid]]. Gas in cuttings is analyzed by grinding a measured amount (approximately 100 mg) of unwashed cuttings in a blender, with any liberated gases analyzed by the standard gas detection system. This analysis is often divided into two components: total gas, comprising all combustible gasses; and petroleum vapors, comprising C2 through C5. This type of analysis can indicate the amount and composition of gases in the formation, even if the larger rock pores are flushed.

Evaluation of oil in cuttings is performed on unwashed and washed bulk cuttings and on individual grains. Evaluation includes visual inspection and analysis using a microscope and ultraviolet (UV) box. Oil shows are described by their physical properties of visual stain, fluorescence, cut, and odor. Care must be taken always to evaluate hydrocarbon shows in cuttings with respect to their petrophysical properties (see review by <ref name=pt03r45>Swanson, R. G., 1981, Sample examination manual: Tulsa, OK, AAPG Methods in Exploration Series, 35 p.</ref>.

Evaluation of oil in cuttings is performed on unwashed and washed bulk cuttings and on individual grains. Evaluation includes visual inspection and analysis using a microscope and ultraviolet (UV) box. Oil shows are described by their physical properties of visual stain, fluorescence, cut, and odor. Care must be taken always to evaluate hydrocarbon shows in cuttings with respect to their petrophysical properties (see review by <ref name=pt03r45>Swanson, R. G., 1981, Sample examination manual: Tulsa, OK, [http://store.aapg.org/detail.aspx?id=603 AAPG Methods in Exploration Series No. 1], 35 p.</ref>.

===Visual stain===

===Visual stain===