US 11,236,584 B2 · Method for continuous downhole cooling of high-temperature drilling fluid

Abstract

The invention discloses a circulating system and a method for continuous downhole cooling of high-temperature drilling fluid. The circulating system includes a cooling water tank, a cooling water injection pump, a plurality of U-shaped pipes, a liquid nitrogen cooling tank, a spiral pipe, a cooling water return pump and a return pipeline. The U-shaped pipe is fixed in an unsealed bond cement gap between outer and inner casings, and two ends are respectively connected with output end of the cooling water injection pump and the spiral pipe. The spiral pipe is disposed in the liquid nitrogen cooling tank; input and output ends of the cooling water return pump are respectively connected with the spiral pipe and the return pipeline; one end of the return pipeline is disposed in the cooling water tank; input end of the cooling water injection pump is connected with the cooling water tank by a pipe.

A method for continuous downhole cooling of high-temperature drilling fluid with a circulating system comprising a cooling water tank, a cooling water injection pump, a plurality of U-shaped pipes, a liquid nitrogen cooling tank, a spiral pipe, a cooling water return pump and a return pipeline, wherein the U-shaped pipes are fixed in an unsealed bond cement gap between an outer casing and an inner casing, and two ends of each of the U-shaped pipes are respectively connected with an output end of the cooling water injection pump and the spiral pipe;

the spiral pipe is disposed in the liquid nitrogen cooling tank;
an input end and an output end of the cooling water return pump are respectively connected with the spiral pipe and the return pipeline;
one end of the return pipeline is disposed in the cooling water tank;
an input end of the cooling water injection pump is connected with the cooling water tank by a pipe, the method comprising the following steps:
step A:
obtaining operating parameters, environmental parameters, well structure parameters and thermal parameters of a target well;
step B:
placing the plurality of U-shaped pipes downward into the unsealed bond cement gap between the outer casing and the inner casing;
step C:
opening the cooling water injection pump and the cooling water return pump at the same time to make a cooling water flow from a wellhead to a downhole location, and then returning along a heat-carrying cooling water pipe of each one of the U-shaped pipes and continuously absorbing heat from the high-temperature drilling fluid in an annulus under effect of forced-convection heat transfer and heat conduction, thereby realizing the continuous downhole circulating and cooling of high-temperature drilling fluid in the annulus;
step D:
calculating a circulating temperature in a drill string, a circulating temperature in the annulus, and a circulating temperature in the heat-carrying cooling water pipe by the following formulas:
formula for temperature control in the drill string:
ρ
m
⁢
A
pipe
⁢
c
m
⁢
∂
T
p
⁢
f
∂
t
=
-
ρ
m
⁢
A
p
⁢
i
⁢
p
⁢
e
⁢
v
p
⁢
i
⁢
p
⁢
e
⁢
c
m
⁢
∂
T
pf
∂
z
+
2
⁢
π
⁢
⁢
R
p
⁢
i
⁢
U
a
⁢
p
⁡
(
T
ann
-
T
pf
)
;
discrete expression of formula for temperature control in the drill string:
B1(Tpf)i−1n+1+(A1−B1+C1)(Tpf)in+1=A1(Tpf)in+C1(Tann)in+1.
formula for temperature control in the annulus:
ρ
m
⁢
A
ann
⁢
c
m
⁢
∂
T
a
⁢
n
⁢
n
∂
t
=
ρ
m
⁢
A
a
⁢
n
⁢
n
⁢
v
a
⁢
n
⁢
n
⁢
c
m
⁢
∂
T
ann
∂
z
-
2
⁢
π
⁢
⁢
R
c
⁢
i
⁢
U
c
⁢
a
⁡
(
T
ann
-
T
c
)
-
2
⁢
π
⁢
⁢
R
pi
⁢
U
a
⁢
p
⁡
(
T
a
⁢
n
⁢
n
-
T
pf
)
;
discrete expression of formula for temperature control in the annulus:
B2(Tann)i−1n+1+(A2−B2−C2−D2)(Tann)in+1=A2(Tann)in−C2(Tc)in+1−D2(Tpf)in+1.
formula for temperature control of the heat-carrying cooling water pipe:
ρ
w
⁢
A
c
⁢
c
w
⁢
∂
T
c
∂
t
=
ρ
w
⁢
A
c
⁢
v
c
⁢
c
w
⁢
∂
T
c
∂
z
+
2
⁢
π
⁢
⁢
R
c
⁢
i
⁢
U
cf
⁡
(
T
f
-
T
c
)
+
2
⁢
π
⁢
⁢
R
c
⁢
i
⁢
U
c
⁢
a
⁡
(
T
ann
-
T
c
)
;
discrete expression of formula for temperature control of the heat-carrying cooling water pipe:
B
3
⁡
(
T
c
)
i
-
1
n
+
1
+
(
A
3
-
B
3
+
C
3
+
D
3
)
⁢
(
T
c
)
i
n
+
1
=
A
3
⁡
(
T
c
)
i
n
+
C
3
⁡
(
T
f
)
i
n
+
1
+
D
3
⁡
(
T
a
⁢
n
⁢
n
)
i
n
+
1
;
⁢
1
U
a
⁢
p
=
1
h
p
⁢
i
+
R
p
⁢
i
R
po
⁢
h
po
+
R
p
⁢
i
K
pipe
⁢
ln
⁡
(
R
p
⁢
o
/
R
p
⁢
⁢
i
)
;
⁢
1
U
cf
=
1
U
c
⁢
a
=
1
h
c
⁢
i
+
R
c
⁢
i
R
c
⁢
o
⁢
h
c
⁢
o
+
R
c
⁢
i
K
c
⁢
ln
⁡
(
R
c
⁢
o
/
R
c
⁢
i
)
;
where, ρm and ρw are respectively densities of the drilling fluid and the cooling water, in kg/m3;
cm and cw are respectively specific heat capacities of drilling fluid and cooling water, in J/(kg·°C.);
A pipe, Aann and Ac are respectively cross-sectional areas of the drill string, the annulus and the heat-carrying cooling water pipe, in m2;
νpipe, νann and νc are respectively flow rates in the drill string, the annulus and the heat-carrying cooling water pipe, in m/s;
Tpf, Tann and Tc are respectively fluid circulating temperatures in the drill string, the annulus and the heat-carrying cooling water pipe, in °C.;
Rpi, Rpo, Rci and Rco are respectively the inner radius of drill string, the outer radius of drill string, the inner radius of heat-carrying cooling water pipe and the outer radius of heat-carrying cooling water pipe, in m;
hpi, hpo, hci and hco are respectively convective heat transfer coefficients between the drilling fluid in the drill string and an inner wall of the drill string, the fluid in the annulus and an outer wall of the drill string, the fluid in the heat-carrying cooling water pipe and the inner wall of the heat-carrying cooling water pipe, and the fluid in the heat-carrying cooling water pipe and the well wall, in W/(m·°C.);
Kpipe and Kc are respectively thermal conductivity of the drill string and the cooling water heating pipe, in W/(m·°C.);
A1, B1 and C1 are respectively constants in the formula for temperature control in the drill string;
A2, B2, C2 and D2 are respectively constants in the formula for temperature control in the annulus;
A3, B3, C3 and D3 are respectively constants in the formula for temperature control of the heat-carrying cooling water pipe;
t represents a circulating time of the drilling fluid, in s;
z represents a length of the drill string or a length of the annulus or a length of the heat-carrying cooling water pipe, in m;
Uap represents a total heat transfer coefficient between the drilling fluid in the annulus and the drilling fluid in the drill string, in W/(m·°C.);
Uca represents a total heat transfer coefficient between the drilling fluid in the heat-carrying cooling water pipe and the drilling fluid in the annulus, in W/(m·°C.);
and Ucf represents a total heat transfer coefficient between the outer casing and a formation, in W/(m·°C.);
step E:
adjusting a speed of the cooling water injection pump and the cooling water return pump according to the circulating temperature respectively in the drill string, the annulus and the heat-carrying cooling water pipe obtained above;
step F:
the cooling water carrying heat flowing into the spiral pipe, and being cooled in the liquid nitrogen cooling tank;
and
step G:
the cooled cooling water being pumped into the return pipe by the cooling water return pump, and being re-injected into the cooling water tank for continued circulating and cooling at a next stage.

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Method for continuous downhole cooling of high-temperature drilling fluid

Life of this patent

Method for continuous downhole cooling of high-temperature drilling fluid

Life of this patent

Abstract

Claims1