Clay detection and quantification using downhole low frequency electromagnetic measurements
AssigneesSaudi Arabian Oil Company, Schlumberger Technology Corporation
InventorsShouxiang Ma, Ping Zhang, Wael Abdallah, Chengbing Liu
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Abstract
Methods and systems are provided for clay detection, clay typing, and clay volume quantification using downhole electromagnetic measurements conducted by a downhole logging tool on a formation at a low frequency less than 5000 Hz. The downhole electromagnetic measurements are used to determine permittivity data that characterizes permittivity of the formation at the low frequency less than 5000 Hz. The downhole low frequency electromagnetic measurements are nondestructive, and the results indicate it is with high sensitivity to the existence of clays.
Claims26
A method for characterizing clay content of a subsurface formation of interest, the method comprising:
- i) configuring and operating a downhole logging tool to conduct a downhole electromagnetic measurement on the formation of interest at a low frequency less than 5000 Hertz, wherein the downhole electromagnetic measurement is used to determine and store permittivity data that characterizes permittivity of the formation of interest at the low frequency less than 5000 Hertz;
- ii) extracting a parameter from the permittivity data that characterizes permittivity of the formation of interest at the low frequency less than 5000 Hertz;
- and
- iii) plotting the permittivity data and comparing the permittivity data to one or more curves of measured permittivity curves obtained from one or more formations known to not have clay, and determining if the formation has clay, and if the formation is determined to have clay, comparing the plot of permittivity data to curves of measured permittivity values of one or more formations having clay types and identifying from the comparison of the plot and curves the clay type for the formation of interest.
A system for characterizing clay content of a subsurface formation of interest, the system comprising:
- a downhole logging tool that is configured to conduct an electromagnetic measurement on the formation of interest at a low frequency less than 5000 Hertz, wherein the electromagnetic measurement measures and stores conductivity data that characterizes complex conductivity of the formation of interest at the low frequency less than 5000 Hertz;
- and
- at least one processor that, when executing program instructions stored in memory, is configured to:
- i) obtain the conductivity data that characterizes complex conductivity of the formation of interest at the low frequency less than 5000 Hertz;
- ii) process the conductivity data of i) to determine permittivity data that characterizes permittivity of the formation of interest at the low frequency less than 5000 Hertz;
- iii) extract a parameter from the permittivity data of ii);
- and
- iv) plotting the permittivity data and comparing the permittivity data to one or more curves of measured permittivity curves obtained from one or more formations known to not have clay, and determining if the formation has clay, and if the formation is determined to have clay, comparing the plot of permittivity data to curves of measured permittivity values of one or more formations having clay types and identifying from the comparison of the plot and curves the clay type for the formation of interest.
Dependencies are inferred from the claim text.