Changes

It is very important that a mudlog be recorded on a standard format using standardized plotting and reporting procedures. This is necessary to allow valid and convenient comparison of log data from well to well and to prevent confusion or misunderstanding over the meaning of a log trace or annotation.

It is very important that a mudlog be recorded on a standard format using standardized plotting and reporting procedures. This is necessary to allow valid and convenient comparison of log data from well to well and to prevent confusion or misunderstanding over the meaning of a log trace or annotation.

==Layout of A mudlog==

==Layout of a mudlog==

 

[[file:mudlogging-the-mudlog_fig1.png|left|thumb|{{figure number|1}}Example of a mudlogging data sheet.]]

mudlogging-the-mudlog_fig1.png|{{figure number|1}}Example of a mudlogging data sheet.

 

mudlogging-the-mudlog_fig2.png|{{figure number|2}}Example of a standard mudlogging form. Note that although efforts are continually being made to standardize mudlog formats, present and previous mudlogs may differ in outline from this example.

[[file:mudlogging-the-mudlog_fig2.png|thumb|{{figure number|2}}Example of a standard mudlogging form. Note that although efforts are continually being made to standardize mudlog formats, present and previous mudlogs may differ in outline from this example.]]

[[:file:mudlogging-the-mudlog_fig2.png|Figure 2]] is an example of the layout and information content of a standard mud log. The general usage of the tracks (columns) on a mudlog are outlined here.

[[:file:mudlogging-the-mudlog_fig2.png|Figure 2]] is an example of the layout and information content of a standard mud log. The general usage of the tracks (columns) on a mudlog are outlined here.

This track gives a relative indication of rock strength and [[porosity]]. Track 1 includes the following information:

This track gives a relative indication of rock strength and [[porosity]]. Track 1 includes the following information:

* ROP and normalized ROP (NROP) (see chapter on “Rate of Penetration”)

* ROP and normalized ROP (NROP) (see [[Rate of penetration]])

* Bit number, type, and diameter

* Bit number, type, and diameter

* Number and size of jets

* Number and size of jets

===Track 2: cuttings lithology===

===Track 2: cuttings lithology===

Track 2 identifies and records the lithology of the cuttings material that arrives at the surface as drilling takes place (see chapter on [[Mudlogging: Drill cuttings analysis]]). Information is commonly presented as lithological symbols, each representing 10% of the total sample volume. This is commonly referred to as a ''percentage log''.

Track 2 identifies and records the lithology of the cuttings material that arrives at the surface as drilling takes place (see chapter on [[Mudlogging: drill cuttings analysis]]). Information is commonly presented as lithological symbols, each representing 10% of the total sample volume. This is commonly referred to as a ''percentage log''.

Some mudlog formats have an interpreted lithology column adjacent to the percent lithology. This interpreted lithology log attempts to take into account factors that might affect cuttings recovery, such as sloughing and trips.

Some mudlog formats have an interpreted lithology column adjacent to the percent lithology. This interpreted lithology log attempts to take into account factors that might affect cuttings recovery, such as sloughing and [[trip]]s.

Additional reservoir information can also be recorded in track 2. In the example log shown in [[:file:mudlogging-the-mudlog_fig2.png|Figure 2]], a separate column is included for qualitative porosity estimation.

Additional reservoir information can also be recorded in track 2. In the example log shown in [[:file:mudlogging-the-mudlog_fig2.png|Figure 2]], a separate column is included for qualitative porosity estimation.

* ''Total combustible hydrocarbons'' from gas trap, mud, cuttings blender tests, and nonformational borehole gas events such as trip gas, carbide lag checks, and connection gas are recorded.

* ''Total combustible hydrocarbons'' from gas trap, mud, cuttings blender tests, and nonformational borehole gas events such as trip gas, carbide lag checks, and connection gas are recorded.

* ''Hydrocarbon chromatograph'' with gaseous alkanes (methane, ethane, propane, butanes, and pentanes) are plotted as individual tracks. Chromatograph calibration checks are also included, providing they do not obscure well data.

* ''Hydrocarbon chromatograph'' with gaseous alkanes (methane, ethane, propane, butanes, and pentanes) are plotted as individual tracks. Chromatograph calibration checks are also included, providing they do not obscure well data.

* ''Oil evaluation'' includes subjective and qualitative evaluation of oil staining and solvent-cut oil. (Many mudloggers include these data in the lithology track.) This evaluation can also include qualitative analysis of oil fluorimetry, refractometry, and geochemistry.

* ''Oil evaluation'' includes subjective and qualitative evaluation of oil staining and solvent-cut oil. (Many mudloggers include these data in the lithology track.) This evaluation can also include qualitative analysis of oil fluorimetry, refractometry, and [[geochemistry]].

===Track 6: geological and lithological evaluation===

===Track 6: geological and lithological evaluation===

[[Category:Wellsite methods]]

[[Category:Wellsite methods]]