Clay content determination by natural gamma ray spectrometry
AssigneeSchlumberger Technology Corporation
InventorGraham Marett
Life of this patent
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Abstract
In accordance with an illustrative embodiment of the present invention, a technique is provided for automatically processing measurements of the total natural gamma radioactivity and the thorium, uranium, potassium contents of formations surrounding a borehole to obtain a representation of the clay content of said formations in a zone of the borehole where the presence of one of said elements, called a disturbing element, is not related to clay. First, reference values of the total radioactivity and the thorium, uranium, potassium contents in the zone are determined. Then, at least two of these measurements are combined in accordance with a function determined from the reference values to produce a representation of the clay content of the formations corrected for the effect of the disturbing element.
Claims30
A method for automatically processing measurements of the total natural gamma radioactivity and the contents of three natural radioactive elements of a formation surrounding a borehole to obtain a representation of the clay content of said formation in a zone of the borehole where the presence of one of said elements, called a disturbing element, is not related to clay, comprising the steps of:
- determining reference values of said measurements in said zone;
- and
- combining at least two of said measurements in accordance with a function determined from said reference values to produce a representation of the clay content of the formation corrected for the effect of said disturbing element.
A method for automatically processing natural gamma ray well logging data to obtain a representation of the clay content of a formation surrounding a borehole in a zone where the presence of a radioactive element, called a disturbing element, is not related to clay, comprising the steps of:
- deriving from said well logging data measurements of the total natural gamma radioactivity and the contents of three natural radioactive elements for said formation;
- determining reference values of said measurements in said zone;
- and
- combining at least two of said measurements in accordance with a function determined from said reference values to produce a representation of the clay content of the formation corrected for the effect of the disturbing element.
An apparatus for automatically processing measurements of the total natural gamma radioactivity and the contents of three natural radioactive elements of a formation surrounding a borehole to obtain a representation of the clay content of said formation in a zone where the presence of one of said elements, called a disturbing element, is not related to clay, comprising:
- means for determining reference values of said measurements in said zone;
- and
- means for combining at least two of said measurements in accordance with a function determined from said reference values to produce a representation of the clay content of the formation corrected for the effect of the disturbing element.
An apparatus for automatically processing natural gamma ray well logging data to obtain a representation of the clay content of a formation surrounding a borehole in a zone where the presence of a radioactive element, called a disturbing element, is not related to clay, comprising:
- means for deriving from said well logging data measurements of the total natural gamma radioactivity and the contents of three natural radioactive elements for said formation;
- means for determining reference values of said measurements in said zone;
- and
- means for combining at least two of said measurements in accordance with a function determined from said reference values to produce a representation of the clay content of the formation corrected for the effect of the disturbing element.
Dependencies are inferred from the claim text.