Formation clay typing from electromagnetic measurements
AssigneesSchlumberger Technology Corporation, Saudi Arabian Oil Company
InventorsPing ZHANG, Wael ABDALLAH, Shouxiang Ma, Chengbing Liu
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Abstract
An array electromagnetic tool is run in a borehole, and resulting signals are processed to provide at least one of real and imaginary conductivity components, σR* and σI*. The at least one of real and imaginary conductivity components is compared to a corresponding representative conductivity component of a plurality of different clay groups and a determination of clay type in the formation is made therefrom.
Claims13
A method for investigating an earth formation traversed by a borehole for clay types, comprising:
- locating an array electromagnetic tool at at least one location in the borehole;
- activating the array electromagnetic tool to generate a signal that interacts with the earth formation and to collect resulting signals;
- processing said resulting signals with a processor and estimating with the processor at least one of real and imaginary conductivity components, σR* and σI* from said resulting signals;
- comparing said at least one of real and imaginary conductivity components to at least one corresponding representative conductivity component of a plurality of different clay groups;
- and
- from said comparing, making a determination of clay type in the formation adjacent the at least one location in the borehole.
A method for investigating an earth formation traversed by a borehole for clay types, comprising:
- locating an array electromagnetic tool at at least one location in the borehole;
- activating the array electromagnetic tool to generate a signal that interacts with the earth formation and to collect resulting signals;
- processing said resulting signals with a processor and estimating with the processor at least one of real and imaginary conductivity components, σR* and σI* from said resulting signals;
- generating at least one set of values representing at least one of real and imaginary conductivity components of a plurality of different clay groups, where said real conductivity component is defined according to
- σ
- R
- =
- S
- w
- n
- 0
- F
-
- [
- σ
- w
- +
- 2
-
-
- m
- 0
-
- β
- +
- ρ
- g
-
- CEC
- 3
-
- (
- F
-
-
- 1
- )
- ]
- with δw representing formation water conductivity, ρg representing matrix grain density, CEC representing the cation exchange capacity of the particular clay group, β+ being the mobility of a counterion in the formation fluid, F being the electric formation factor defined according to F=ϕ−m0, where ϕ is the porosity and m0 is a cementation exponent for a shaly formation, Sw being the water saturation, and n0 being a saturation exponent, and where said imaginary conductivity component is defined according to σI=⅔β+sfρgSwn0-1CEC, with f being the fraction of counterions in the Stern layer, and β+s being the mobility of the counterion within a Stern layer;
- comparing said at least one of real and imaginary conductivity components to at least one corresponding said sets of values;
- and
- from said comparing, making a determination of clay type in the formation adjacent the at least one location in the borehole.
Dependencies are inferred from the claim text.