Changes

  | isbn    = 0891816607

  | isbn    = 0891816607

}}

}}

''Cuttings'' are the small pieces of rock that are chipped away by the bit while a well is being drilled. The rock fragments are transported by the mudstream from the bit to the surface where they can be “caught” and analyzed (see chapter on [[Land rigs]]).

''Cuttings'' are the small pieces of rock that are chipped away by the bit while a well is being drilled. The rock fragments are transported by the mudstream from the bit to the surface where they can be “caught” and analyzed (see [[Land rigs]]).

Drill cuttings are important because they are often the only physical lithological data that are recovered from a well. These data are used as supportive information for subsequent [[show evaluation]], correlation of lithology to wireline logs, and other special geological, geophysical, or engineering analyses (see chapter on [[Show evaluation]]). Some of the activities that utilize data obtained from drill cuttings are summarized as follows:

Drill cuttings are important because they are often the only physical lithological data that are recovered from a well. These data are used as supportive information for subsequent [[show evaluation]], correlation of lithology to wireline logs, and other special geological, geophysical, or engineering analyses (see [[Show evaluation]]). Some of the activities that utilize data obtained from drill cuttings are summarized as follows:

* [[Show evaluation]]

* [[Show evaluation]]

===Sample interval===

===Sample interval===

Both the sample interval and the number and types of sample sets are usually determined at the start of the well (see chapter on [[Well planning]]). Typically, drill cuttings are caught or collected as composite samples that reflect the various lithologies drilled over a 10-ft interval. The interval length can vary depending on the drilling rate and the detail needed for reservoir and lithological descriptions. When the drill rate is low, it is important to collect a sample that is representative of the whole interval drilled and not just the final few feet. It is also important to collect representative samples when drill rates are excessively high and it is physically difficult for the mudlogger to collect and analyze all of the samples accurately. In this situation, the sample interval can be increased or an additional mudlogger can be assigned to the tour. Also, it is not unreasonable to request that the drill rate be slowed so that better samples can be obtained and used to evaluate prospective reservoir zones and casing or kick-off points.

Both the sample interval and the number and types of sample sets are usually determined at the start of the well (see [[Well planning]]). Typically, drill cuttings are caught or collected as composite samples that reflect the various lithologies drilled over a 10-ft interval. The interval length can vary depending on the drilling rate and the detail needed for reservoir and lithological descriptions. When the drill rate is low, it is important to collect a sample that is representative of the whole interval drilled and not just the final few feet. It is also important to collect representative samples when drill rates are excessively high and it is physically difficult for the mudlogger to collect and analyze all of the samples accurately. In this situation, the sample interval can be increased or an additional mudlogger can be assigned to the tour. Also, it is not unreasonable to request that the drill rate be slowed so that better samples can be obtained and used to evaluate prospective reservoir zones and casing or kick-off points.

When a drilling break or change in background gas occurs, supplemental samples should also be caught to aid in show evaluation.

When a drilling break or change in background gas occurs, supplemental samples should also be caught to aid in show evaluation.

===Sampling location===

===Sampling location===

Drill cuttings are typically collected from the rig shale shakers, a sluice box in the possum belly, or the desander/desilter outlets (see “Land Rigs” chapter).

Drill cuttings are typically collected from the rig shale shakers, a sluice box in the possum belly, or the desander/desilter outlets (see [[Land rigs]]).

===Shale shaker===

===Shale shaker===

==Sample lag==

==Sample lag==

Because there is a time difference between when the rock is first broken away from the formation and when the sample is caught at the surface, all cuttings samples should be “lagged” or adjusted to the proper depth (see chapter on [[Wellsite math]]). This process is critical in showing evaluation and lithological correlation.

Because there is a time difference between when the rock is first broken away from the formation and when the sample is caught at the surface, all cuttings samples should be “lagged” or adjusted to the proper depth (see [[Wellsite math]]). This process is critical in showing evaluation and lithological correlation.

==Sample preparation==

==Sample preparation==

===Wet-cut sample===

===Wet-cut sample===

A small portion of the unwashed wet-cut sample is set aside and used for blender gas analysis (see chapter on “Mudlogging: Gas Extraction and Monitoring”). Although this sample should not be rigorously washed, discretion can be used in lightly rinsing the sample to remove surface drilling mud film. The remainder of the sample is packaged for later analysis and archiving.

A small portion of the unwashed wet-cut sample is set aside and used for blender gas analysis (see [[Mudlogging: gas extraction and monitoring]]). Although this sample should not be rigorously washed, discretion can be used in lightly rinsing the sample to remove surface drilling mud film. The remainder of the sample is packaged for later analysis and archiving.

===Dry-cut sample===

===Dry-cut sample===