# US 10,370,957 B2 · Measuring downhole temperature by combining DAS/DTS data

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- Number: US 10,370,957 B2
- Document ID: US10370957B2
- Status: Granted
- Kind: B2
- Application number: 15/453,216
- Filed: 2017-03-08
- Published: 2017-09-14
- Granted: 2019-08-06
- Earliest claimed: 2016-03-09
- Assignees: ConocoPhillips Company
- Applicants: Conocophillips Company
- Inventors: Ge Jin; Herbert W. Swan; Baishali Roy; Kyle R. Krueger
- Web page: https://patentgrep.com/patent/US10370957B2

## CPC

- E21B 47/07: Temperature
- E21B 43/26: by forming crevices or fractures
- E21B 47/0224: using seismic or acoustic means
- E21B 47/0228: using electromagnetic energy or detectors therefor
- E21B 47/107: using acoustic means
- E21B 47/113: using electrical indications; using light radiations
- E21B 47/135: using light waves, e.g. infrared or ultraviolet waves
- G01B 11/161: {by interferometric means}
- G01H 9/004: {using fibre optic sensors (light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125)}
- G01K 11/32: using changes in transmittance, scattering or luminescence in optical fibres
- G01V 1/226: {Optoseismic systems}
- G01V 1/40: specially adapted for well-logging
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01H: MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00)
- G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02)

## Abstract

This disclosure describes a method of combining DAS and DTS data to accurately estimate borehole temperature. The described method takes advantage of the thermal sensitivity of DAS signal in the low-frequency band, and combines with the absolute temperature measurement from DTS, to produce a distributed temperature estimation that is up to 10000 more accurate than the current commercial solution. The DAS and DTS data should be record simultaneously at the same well. The DAS data are first low-pass filtered and then converted into temperature variation measurement. Then an accurate temperature estimation is obtained by fitting both DTS and DAS data.

## Claims

### Claim 1

A method of measuring temperature variations along a wellbore, the method comprising:
a) providing one or more fiber optic cables along a length of a wellbore;
b) recording distributed acoustic sensing (DAS) signals along the wellbore well using at least one fiber optic cable;
c) simultaneously recording distributed temperature sensing (DTS) signals from the well using at least one fiber optic cable;
d) low-pass filter and down-sample the DAS signals to obtain low-frequency DAS data;
e) converting the low-frequency DAS data to temperature variation using the following equation (1):
wherein D(x,t) is the low-frequency DAS, μ is the constant that converts optical phase rate to temperature variation, β(t) is the drift noise existing in the DAS data;
f) estimating borehole temperature by minimizing the error function c using the following equation (2):
ɛ
=

T
-
T
0

+
λ
⁢

dT
dt
-
μ
⁢
⁢
D
-
β

(
2
)
wherein T0 is the DTS data, D is inverted DAS data, and λ is a parameter that determines the relative importance of minimizing the DAS data misfit, as compared to DTS misfit, and λ may be frequency dependent.

### Claim 2 (depends on 1)

The method of claim 1, wherein said one or more fiber optic cables are embedded in a cement of the wellbore.

### Claim 3 (depends on 1)

The method of claim 1, wherein said one or more fiber optic cables is included in a coiled tubing string, a wireline, or a carbon rod in the wellbore.

### Claim 4 (depends on 1)

The method of claim 1, wherein DAS and DTS signals are obtained at 0-1 Hz.

### Claim 5 (depends on 1)

The method of claim 1, wherein DAS and DTS signals are sampled at more than 1 kHz, preferably more than 5 kHz, more preferably more than 10 kHz to avoid aliasing from a high-frequency band.

### Claim 6 (depends on 1)

The method of claim 1, wherein recorded DAS signals are low-pass filtered at 0.001-1 Hz and sub-sampled to a 1-second sample rate.

### Claim 7 (depends on 1)

The method of claim 1, wherein DAS and DTS signals are obtained at 0-1 Hz and sampled at more than 1 kHz, preferably more than 5 kHz, more preferably more than 10 kHz to avoid aliasing from a high-frequency band.

### Claim 8 (depends on 1)

The method of claim 1, wherein the wellbore is undergoing fracturing, shut-in, production, steam/water injection, or a combination thereof.