# US 2024/0201414 A1 · Water saturation and cation exchange capacity from logging-while-drilling electromagnetic measurements

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- Number: US 2024/0201414 A1
- Document ID: US20240201414A1
- Status: Published application
- Kind: A1
- Application number: 18/553,628
- Filed: 2021-04-28
- Published: 2024-06-20
- Earliest claimed: 2021-04-28
- Assignees: Schlumberger Technology Corporation; Saudi Arabian Oil Company
- Applicants: Schlumberger Technology Corporation; Saudi Arabian Oil Company
- Inventors: Ping Zhang; Gong Li Wang; Wael Abdallah; Dean Homan; Shouxiang Ma
- Web page: https://patentgrep.com/patent/US20240201414A1

## CPC

- G01N 27/04: by investigating resistance
- G01V 3/38: Processing data, e.g. for analysis, for interpretation, for correction
- E21B 7/04: Directional drilling
- E21B 44/00: Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions
- E21B 49/00: Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
- E21B 49/0875: {determining specific fluid parameters}
- G01V 3/26: operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device (with electromagnetic waves G01V3/30)
- G01V 3/30: operating with electromagnetic waves
- E21B 2200/20: Computer models or simulations, e.g. for reservoirs under production, drill bits
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02)
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS

## Abstract

A method for characterizing a subterranean formation is provided that involves obtaining resistivity log data measured by a logging-while-drilling electromagnetic tool operated while drilling a wellbore that traverses the subterranean formation, and calculating at least one of a first data value representing water saturation of the subterranean formation and a second data value representing cation exchange capacity (CEC) of the subterranean formation from the resistivity log data. In embodiments, the method can further involve storing at least one of the first data value and the second data value in computer memory, and/or outputting at least one of the first data value and the second data value as part of a log for well placement, formation evaluation. geological modeling, or reservoir management. The first data value and/or the second data value can also be used for geo-steering the drilling of the wellbore.

## Claims

### Claim 1

A method of characterizing a subterranean formation, comprising:
obtaining resistivity log data measured by a logging-while-drilling electromagnetic tool operated while drilling a wellbore that traverses the subterranean formation; and
calculating at least one of a first data value representing water saturation of the subterranean formation and a second data value representing cation exchange capacity (CEC) of the subterranean formation from the resistivity log data.

### Claim 2 (depends on 1)

A method according to claim 1, further comprising:
storing at least one of the first data value and the second data value in computer memory.

### Claim 3 (depends on 1)

A method according to claim 1, further comprising:
outputting at least one of the first data value and the second data value as part of a log for well placement, formation evaluation, geological modeling, or reservoir management.

### Claim 4 (depends on 1)

A method according to claim 1, further comprising:
using at least one of the first data value and the second data value for geo-steering the drilling of the wellbore.

### Claim 5 (depends on 1)

A method according to claim 1, wherein:
the first data value representing water saturation of the subterranean formation is calculated using a relationship involving an in-phase conductivity component, a quadrature-phase conductivity component, and a first plurality of formation parameters; and
the in-phase conductivity component and the quadrature-phase conductivity component are determined by inversion of the resistivity log data measured by the logging-while-drilling electromagnetic tool.

### Claim 6 (depends on 5)

A method according to claim 5, wherein:
the first plurality of formation parameters comprises water conductivity.

### Claim 7 (depends on 6)

A method according to claim 6, wherein:
said water conductivity is calculated using water salinity and formation temperature.

### Claim 8 (depends on 7)

A method according to claim 7, wherein:
said water salinity and formation temperature are determined using at least one formation water sample.

### Claim 9 (depends on 5)

A method according to claim 5, wherein:
the first plurality of formation parameters further comprise an electric formation factor and a parameter based on grain density, counter-ion mobility, and fraction of counter-ion.

### Claim 10 (depends on 9)

A method according to claim 9, wherein:
the first plurality of formation parameters further comprise an additional parameter based on grain density, counter-ion mobility, and electric formation factor.

### Claim 11 (depends on 1)

A method according to claim 1, wherein:
the second data value representing CEC of the subterranean formation is calculated using a relationship involving a quadrature-phase conductivity component, the first data value representing water saturation of the subterranean formation, and a second plurality of formation parameters; and
the quadrature-phase conductivity component is determined by inversion of the resistivity log data measured by the logging-while-drilling electromagnetic tool.

### Claim 12 (depends on 11)

A method according to claim 11, wherein:
the second plurality of formation parameters comprise a parameter based on grain density, counter-ion mobility and fraction of counter-ion.

### Claim 13 (depends on 1)

A method according to claim 1, wherein:
the calculating of the at least one of the first data value and the second data value is based on knowledge about the subterranean formation obtained from laboratory measurements and/or measurement logs.

### Claim 14 (depends on 1)

A method according to claim 1, wherein:
the subterranean formation comprises clay.

### Claim 15 (depends on 14)

A method according to claim 14, wherein:
the subterranean formation comprises a shaly-sand formation.

### Claim 16 (depends on 1)

A method according to claim 1, wherein:
the resistivity log data comprises attenuation and phase-shift measurements performed by the logging-while-drilling electromagnetic tool.

### Claim 17 (depends on 16)

A method according to claim 16, wherein:
the attenuation and phase-shift measurements are performed at frequencies in the KHz to MHz range.

### Claim 18 (depends on 1)

A method according to claim 1, wherein:
the logging-while-drilling electromagnetic tool is part of a bottom hole assembly that includes a rotary drill bit.

### Claim 19 (depends on 1)

A method according to claim 1, wherein:
the logging-while-drilling electromagnetic tool comprises a propagation type resistivity tool.

### Claim 20 (depends on 1)

A method according to claim 1, wherein:
the resistivity log data is obtained at different depths in the wellbore in order to investigate different parts of the subterranean formation that is traversed by the wellbore while drilling the wellbore.

### Claim 21 (depends on 20)

A method according to claim 20, further comprising:
processing the resistivity log data at respective depths in order to calculate at least one of the first data value and the second data value at the different depths.