# US 11,441,422 B2 · Methods and systems for reservoir characterization and optimization of downhole fluid sampling

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,441,422 B2
- Document ID: US11441422B2
- Status: Granted
- Kind: B2
- Application number: 16/152,114
- Filed: 2018-10-04
- Published: 2019-04-11
- Granted: 2022-09-13
- Earliest claimed: 2017-10-06
- Assignees: Schlumberger Technology Corporation
- Applicants: Schlumberger Technology Corporation
- Inventors: Morten Kristensen; Nikita Chugunov
- Web page: https://patentgrep.com/patent/US11441422B2

## CPC

- E21B 49/10: using side-wall fluid samplers or testers
- E21B 49/084: {with means for conveying samples through pipe to surface}
- E21B 49/088: {combined with sampling}
- E21B 49/0875: {determining specific fluid parameters}
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS

## Abstract

A method (and corresponding downhole tool) is provided for downhole fluid analysis of formation fluids. The downhole tool is operated to draw live fluid from the formation through the downhole tool and acquire observed sensor measurements of the live fluid (which includes filtrate contamination) that flows through the downhole tool. The observed sensor measurements are used in an inversion process that solves for a set of input parameter values of a computational model that predicts level of filtrate contamination in the live fluid that flows through the downhole tool. The set of input parameter values includes at least one endpoint value for the observed sensor measurements. The set of input parameter values solved by the inversion process can be stored and output for different applications.

## Claims

### Claim 1

A method for downhole fluid analysis of formation fluids, comprising:
using a downhole tool positioned in a wellbore that traverses a subterranean formation, operating the downhole tool to draw a live fluid from the formation through the downhole tool and acquire observed sensor measurements of the live fluid that flows through the downhole tool, wherein the live fluid includes filtrate contamination;
using the observed sensor measurements in an inversion process that solves for a set of input parameter values of a proxy model that predicts a level of filtrate contamination in the live fluid that flows through the downhole tool, wherein the set of input parameter values comprises at least one endpoint value for the observed sensor measurements, wherein the inversion process comprises using at least one objective function chosen from:
min
X
⁢
∫
V
⁢
W
⁡
(
V
)
⁢

-
O
⁢
D
⁡
(
x
)

⁢
dV
,
wherein is an observed optical density, OD(x) is a predicted optical density output by the proxy model, W(V) is a weight-vector, and x is a vector of input parameters including the set of input parameter values and optical density endpoints for the live fluid and a pure filtrate; or
min
X
⁢
∫
V
⁢
{
W
O
⁢
D
⁡
(
V
)
⁢

-
O
⁢
D
⁡
(
x
)

+
W
G
⁢
O
⁢
R
⁡
(
V
)
⁢

f
^
-
f
⁡
(
x
)

+
W
b
⁡
(
V
)
⁢

b
^
-
b
⁡
(
x
)

+
W
ρ
⁡
(
V
)
⁢

ρ
^
-
ρ
⁡
(
x
)

}
⁢
dV
,
wherein is an observed optical density, OD(x) is a predicted optical density output by the proxy model, {circumflex over (ƒ)} is an observed GOR-related ƒ-function, ƒ(x) is a predicted GOR-related ƒ-function output by the proxy model, {circumflex over (b)} is an observed shrinkage factor, b(x) is a predicted shrinkage factor output by the proxy model, {circumflex over (ρ)} is an observed mass density, ρ(x) is a predicted mass density output by the proxy model, WOD(V), WCOR(V), and Wρ(V) are weight vectors, and x is a vector of input parameters including the optical density endpoints for the live fluid and a pure filtrate and one or more other input parameters; and wherein the inversion is repeated until a stopping criteria is met for the at least one objective function; and
storing and outputting the set of input parameter values solved by the inversion process.

### Claim 2 (depends on 1)

A method according to claim 1, further comprising:
using the set of input parameter values solved by the inversion process to calibrate the proxy model;
using the calibrated proxy model to predict the level of filtrate contamination in the live fluid; and
comparing the predicted level of filtrate contamination to a threshold level and performing at least one operational action of the downhole tool in response to the comparing.

### Claim 3 (depends on 2)

A method according to claim 2, wherein:
the threshold level indicates that the live fluid is sufficiently clean; and
the at least one operational action is selected from the group consisting of: fluid analysis measurements of the live fluid, collection of at least one sample of the live fluid, or a combination thereof.

### Claim 4 (depends on 1)

A method according to claim 1, wherein:
the observed sensor measurements further comprise an additional fluid sensor measurement; and
the at least one endpoint value of the set of input parameter values further comprises at least one additional endpoint value of the additional fluid sensor measurement for a clean formation fluid.

### Claim 5 (depends on 4)

A method according to claim 4, wherein:
the at least one endpoint value of the set of input parameter values further comprises at least one additional endpoint value of the additional fluid sensor measurement for the filtrate that contaminates the live fluid.

### Claim 6 (depends on 1)

A method according to claim 1, wherein:
the set of input parameter values further includes at least one parameter value that characterizes rock properties of the formation.

### Claim 7 (depends on 6)

A method according to claim 6, wherein:
the at least one parameter value that characterizes rock properties of the formation comprises at least one parameter value that is based on the vertical permeability kν of the formation and the horizontal permeability kh of the formation.

### Claim 8 (depends on 1)

A method according to claim 1, wherein:
the set of input parameter values further includes at least one parameter value that characterizes formation fluid properties.

### Claim 9 (depends on 8)

A method according to claim 8, wherein:
the at least one parameter value that characterizes formation fluid properties comprises at least one parameter value that is based on uncontaminated formation fluid viscosity μo and filtrate viscosity μƒ.

### Claim 10 (depends on 1)

A method according to claim 1, wherein:
the set of input parameter values further includes at least one parameter value that characterizes wellbore properties.

### Claim 11 (depends on 10)

A method according to claim 10, wherein:
the at least one parameter value that characterizes wellbore properties is based on at least one of: radius of filtrate invasion as measured from the borehole wall, formation thickness, and relative tool distance from the top of formation.

### Claim 12 (depends on 1)

A method according to claim 1, wherein:
the set of input parameter values solved by the inversion process is used to display formation rock properties or formation fluid properties for reservoir understanding.

### Claim 13 (depends on 1)

A method according to claim 1, wherein:
the set of input parameter values solved by the inversion process is used as formation rock properties or formation fluid properties for reservoir optimization.

### Claim 14 (depends on 1)

A method according to claim 1, wherein:
the observed sensor measurements of the live fluid are carried out with the live fluid flowing from the formation into the downhole tool at a constant rate; and
the proxy model predicts the level of filtrate contamination in the live fluid that flows through the downhole tool at the constant rate as a function of cleanup volume.

### Claim 15 (depends on 1)

A method according to claim 1, further comprising:
using the at least one endpoint value for the observed sensor measurements as solved by the inversion process to predict the level of filtrate contamination in the live fluid flowing through the downhole tool.

### Claim 16 (depends on 1)

A method according to claim 1, wherein:
the proxy model is configured to mimic or represent the output response of a numeric simulation of cleanup operations.

### Claim 17 (depends on 1)

A method according to claim 1, further comprising:
using the set of input parameter values solved by the inversion process to calibrate the proxy model;
using the calibrated proxy model to determine at least one optimized rate of fluid flow through the downhole tool which minimizes a predicted remaining cleanup time required to reach a predetermined threshold contamination level; and
performing real-time control of the downhole tool such that the flow rate of the live fluid drawn through the downhole tool matches the at least one optimized rate.

### Claim 18 (depends on 17)

A method according to claim 17, wherein:
the downhole tool includes a sample line and guard line; and
the calibrated proxy model is used to determine a first optimized rate Qs of fluid flow through the sample line and a second optimized rate Qg of fluid flow through the guard line, wherein the first and second optimized rates Qs, Qg minimize a predicted remaining cleanup time required to reach the predetermined threshold contamination level.

### Claim 19 (depends on 18)

A method according to claim 18, wherein:
the calibrated proxy model is evaluated over a number of combinations of rates of fluid flow through the sample line and the guard line to determine a predicted remaining cleanup time required to reach a predetermined threshold contamination level for each combination of rates, and the particular combination of rates with a minimum predicted remaining cleanup time is selected as the first and second optimized rates Qs, Qg.

### Claim 20

A downhole tool configured for fluid analysis of formation fluids, the downhole tool comprising:
at least one fluid sensor that acquires observed sensor measurements of a live fluid that flows through the downhole tool, wherein the live fluid includes filtrate contamination; and
at least one processor that is configured to use the observed sensor measurements in an inversion process that solves for a set of input parameter values of a proxy model that predicts a level of filtrate contamination in the live fluid, wherein the set of input parameter values comprises at least one endpoint value for the observed sensor measurements, wherein the at least one processor is further configured to store and output the set of input parameter values solved by the inversion process, and wherein the inversion process comprises using at least one objective function chosen from:
min
X
⁢
∫
V
⁢
W
⁡
(
V
)
⁢

-
O
⁢
D
⁡
(
x
)

⁢
dV
,
wherein is an observed optical density, OD(x) is a predicted optical density output by the proxy model, W(V) is a weight-vector, and x is a vector of input parameters including the set of input parameters and the optical density endpoints for the live fluid and a pure filtrate; or
min
X
⁢
∫
V
⁢
{
W
O
⁢
D
⁡
(
V
)
⁢

-
O
⁢
D
⁡
(
x
)

+
W
G
⁢
O
⁢
R
⁡
(
V
)
⁢

f
^
-
f
⁡
(
x
)

+
W
b
⁡
(
V
)
⁢

b
^
-
b
⁡
(
x
)

+
W
ρ
⁡
(
V
)
⁢

ρ
^
-
ρ
⁡
(
x
)

}
⁢
dV
,
wherein is an observed optical density, OD(x) is a predicted optical density output by the proxy model, {circumflex over (ƒ)} is an observed GOR-related ƒ-function, ƒ(x) is a predicted GOR-related ƒ-function output by the proxy model, {circumflex over (b)} is an observed shrinkage factor, b(x) is a predicted shrinkage factor output by the proxy model, {circumflex over (ρ)} is an observed mass density, ρ(x) is a predicted mass density output by the proxy model, WOD(V), WGOR(V), and Wρ(V) are weight vectors, and x is a vector of input parameters including optical density endpoints for the live fluid and a pure filtrate and one or more other input parameters; and wherein the inversion is repeated until a stopping criteria is met for the at least one objective function.

### Claim 21 (depends on 20)

A downhole tool according to claim 20, wherein the at least one processor is further configured to:
use the set of input parameter values solved by the inversion process to calibrate the proxy model;
use the calibrated proxy model to predict the level of filtrate contamination in the live fluid; and
compare the predicted level of filtrate contamination to a threshold level and initiate at least one operational action of the downhole tool in response to the comparing.

### Claim 22 (depends on 21)

A downhole tool according to claim 21, wherein:
the threshold level indicates that the live fluid is sufficiently clean; and
the at least one operational action is selected from the group consisting of: fluid analysis measurements of the live fluid, collection of at least one sample of the live fluid, or a combination thereof.

### Claim 23 (depends on 20)

A downhole tool according to claim 20, wherein the at least one processor is further configured to:
use the set of input parameter values solved by the inversion process to calibrate the proxy model;
use the calibrated proxy model to determine at least one optimized rate of fluid flow through the downhole tool which minimizes a predicted remaining cleanup time required to reach a predetermined threshold contamination level; and
perform real-time control of the downhole tool such that the flow rate of the live fluid drawn through the downhole tool matches the at least one optimized rate.

### Claim 24 (depends on 23)

A downhole tool according to claim 23, further comprising:
a sample line and a guard line;
wherein the at least one processor is further configured to use the calibrated proxy model to determine a first optimized rate Qs of fluid flow through the sample line and a second optimized rate Qq of fluid flow through the guard line, wherein the first and second optimized rates Qs, Qg minimize a predicted remaining cleanup time required to reach the predetermined threshold contamination level.

### Claim 25 (depends on 20)

A downhole tool according to claim 20, wherein:
the downhole tool comprises a wireline tool.

### Claim 26 (depends on 20)

A downhole tool according to claim 20, wherein:
the downhole tool comprises a while-drilling tool.

### Claim 27

A downhole tool configured for fluid analysis of formation fluids, the downhole tool comprising:
at least one fluid sensor that acquires observed sensor measurements of a live fluid that flows through the downhole tool, wherein the live fluid includes filtrate contamination; and
at least one processor that is configured to use the observed sensor measurements in an inversion process that solves for a set of input parameter values of a proxy model that predicts a level of filtrate contamination in the live fluid;
wherein the at least one processor is further configured to use the set of input parameter values solved by the inversion process to calibrate the proxy model, use the calibrated proxy model to determine at least one optimized rate of fluid flow through the downhole tool which minimizes a predicted remaining cleanup time required to reach a predetermined threshold contamination level, and perform real-time control of the downhole tool such that the flow rate of the live fluid drawn through the downhole tool matches the at least one optimized rate, wherein the inversion process comprises using at least one objective function chosen from:
min
X
⁢
∫
V
⁢
W
⁡
(
V
)
⁢

-
O
⁢
D
⁡
(
x
)

⁢
dV
,
wherein is an observed optical density, OD(x) is a predicted optical density output by the proxy model, W(V) is a weight-vector, and x is a vector of input parameters including the set of input parameter values and optical density endpoints for the live fluid and a pure filtrate; or
min
X
⁢
∫
V
⁢
{
W
O
⁢
D
⁡
(
V
)
⁢

-
O
⁢
D
⁡
(
x
)

+
W
G
⁢
O
⁢
R
⁡
(
V
)
⁢

f
^
-
f
⁡
(
x
)

+
W
b
⁡
(
V
)
⁢

b
^
-
b
⁡
(
x
)

+
W
ρ
⁡
(
V
)
⁢

ρ
^
-
ρ
⁡
(
x
)

}
⁢
dV
,
wherein is an observed optical density, OD(x) is a predicted optical density output by the proxy model, {circumflex over (ƒ)} is an observed GOR-related ƒ-function, ƒ(x) is a predicted GOR-related ƒ-function output by the proxy model, {circumflex over (b)} is an observed shrinkage factor, b(x) is a predicted shrinkage factor output by the proxy model, {circumflex over (ρ)} is an observed mass density, ρ(x) is a predicted mass density output by the proxy model, WOD(V), WGOR(V), and Wρ(V) are weight vectors, and x is a vector of input parameters including optical density endpoints for the live fluid and a pure filtrate and one or more other input parameters; and wherein the inversion is repeated until a stopping criteria is met for the at least one objective function.