Changes

Various gas ratios can be used depending on the data available. The most common gas ratios used are those with the most separation (C5/C1) and those with the heaviest composition (C4/C1 or C5/C1). Because gas ratio analysis is empirical in nature, it can sometimes prove inconclusive. However, the following “rules of thumb” can be useful<ref name=pt03r17>Exploration Logging, Inc., 1985, Mud Logging: Principles and Interpretations. Boston, MA, IHRDC, 92 p.</ref>:

Various gas ratios can be used depending on the data available. The most common gas ratios used are those with the most separation (C5/C1) and those with the heaviest composition (C4/C1 or C5/C1). Because gas ratio analysis is empirical in nature, it can sometimes prove inconclusive. However, the following “rules of thumb” can be useful<ref name=pt03r17>Exploration Logging, Inc., 1985, Mud Logging: Principles and Interpretations. Boston, MA, IHRDC, 92 p.</ref>:

* Zones with a high C1 value may represent dry gas, [[coal]], biogenic gas, or a water wet zone.

* Zones with a high C1 value may represent [[dry gas]], [[coal]], biogenic gas, or a water wet zone.

* Wet gas zones commonly have a C1 /C3 ratio that is higher than the C1 /C4 ratio.

* Wet gas zones commonly have a C1 /C3 ratio that is higher than the C1 /C4 ratio.

* Nonproductive zones tend to have a ratio trend where subsequent values are lower than preceding values.

* Nonproductive zones tend to have a ratio trend where subsequent values are lower than preceding values.