Systems and methods for controlling flow rate in a focused downhole acquisition tool

Patent metadata

Field	Value
Publication number	US-10294784-B2
Application number	US-201514956338-A
Country	US
Kind code	B2
Filing date	Dec 1, 2015
Priority date	Dec 1, 2015
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

A method includes operating a downhole acquisition tool including a guard probe and a sample probe in a wellbore that contains a fluid that includes a native reservoir fluid and a contaminant. The method also includes receiving a first portion of fluid into the guard probe and a second portion of fluid into the sample probe, estimating a contamination level of the first or second portions based on a fluid property of the respective first and second portions, determining an initial guard flow rate of the first portion, determining an initial sample flow rate of the second portion, using a processor to adjust a guard flow rate of the second portion over pump time after the contamination level of the first portion is at or below a contamination level threshold, and adjust a sample flow rate of the first portion based on the adjusted guard flow rate and total flowrate.

First claim

The invention claimed is:

1. A method comprising:
operating a downhole acquisition tool comprising a guard probe and a sample probe in a wellbore in a geological formation, wherein the wellbore or the geological formation, or both contains a fluid that comprises a native reservoir fluid of the geological formation and a contaminant;
receiving a first portion of the fluid into the guard probe and a second portion of the fluid into the sample probe;
estimating a contamination level of the first portion of the fluid, the second portion of the fluid, or a combination thereof based on a fluid property of the respective first and second portions of the fluid as measured by the downhole acquisition tool;
determining an initial guard flow rate of the first portion of fluid through the guard probe;
determining an initial sample flow rate of the second portion of fluid through the sample probe;
using a processor to:
adjust a guard flow rate of the second portion of the fluid through the guard probe over pump time after the contamination level of the first portion of the fluid is at or below a contamination level threshold, based on the initial guard flow rate and a cumulative contamination level of the first and second portion of the fluid; and
adjust a sample flow rate of the first portion of the fluid through the sample probe based on the adjusted guard flow rate and the total flowrate.

2. The method of claim 1 , wherein the cumulative contamination level is a weighted average contamination of the fluid over the pump time, wherein the guard flow rate is further determined based on the weight rated contamination of the fluid.

3. The method of claim 1 , wherein determining the guard flow rate further comprises applying a guard efficiency factor to correct for changes in guarding efficiency of the guard probe.

4. The method of claim 1 , wherein determining the guard flow rate accords with the following relationship:

Q
g

⁡

(

t
+

Δ
⁢

⁢
t

)

=

(

η
tot

⁡

(
t
)

-

η
sd

η
g

⁡

(

T
d

)

⁢

(

t
+

Δ
⁢

⁢
t

T
d

)

-
n

-

η
sd

)

⁢

Q
tot

⁡

(
t
)

where
Q g represents the guard flow rate of the guard probe;
Q tot represents a total flow rate of the downhole acquisition tool;
η tot represents a total flow rate weighted average contamination level of the fluid;
η sd represents a contamination level threshold of the first portion of the fluid;
T d represents the earliest time the contamination level of the first portion reaches the contamination level threshold;
n represents a parameter of the probe sampling or an adjustment parameter; and
t represents pump-out time of the first and second portions of the fluid.

5. The method of claim 4 , wherein time is replaced by pumpout volume.

6. The method of claim 1 , wherein determining the guard flow rate accords with the following relationship:

Q
g

⁡

(

t
+

Δ
⁢

⁢
t

)

=

(

η

n
tot

⁡

(
t
)

-

η

n
sd

η

n
g

⁡

(

T
d

)

Assignees

• Schlumberger Technology Corp

Inventors

• Gisolf Adriaan
• Hsu Kai
• Chang Yong
• Zuo Youxiang
• Lee Ryan Sangjun
• Partouche Ashers

Classifications

• G01N1/14

  Suction devices, e.g. pumps; Ejector devices · CPC title

• E21B47/12

  Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling · CPC title

• E21B2049/085

  Fixed Constructions · mapped topic

• E21B49/081 Primary

  with down-hole means for trapping a fluid sample (E21B49/10 takes precedence) · CPC title

• E21B49/10 Primary

  using side-wall fluid samplers or testers · CPC title