218
G. Zhang et al.
3 Results Analysis
In order to analyze the variation law of CML dual-gradient drilling wellbore temperature
in the circulating process, the example well data in reference [16] for calculation. The
water depth of the well is 1500 m, the slurry level is located at 200 m below the sea
surface, the drilling fluid displacement is 30L/s, the geothermal gradient is 2.5 °C/100 m,
the mud inlet temperature is 25 °C, the sea surface temperature is 20 °C. The parameters
of well depth results and other basic parameters are shown in Table 1 and 2.
Table 1. Well depth structure parameters
String
type
Diameter/mm Length/m Depth/m
Drill
string
127.00
5000
0–3000
Marine
riser
533.40
1500
0–1500
Casing 273.05
3550
1500–4550
Naked
eye
215.90
50
4550–5000
Return
line
152.40
1000
0–1000
Table 2. Basic parameters
Thermophysical parameters
Sea
Drilling fluid
Cement
String
Rock
Conductivity
W /m · ◦ C
0.60
1.73
1.00
43.75
2.25
density
g/cm 3
1.03
1.50
1.90
7.80
2.64
Specific heat
J /g · ◦ C
4.18
3.94
2.00
6.40
0.84
3.1 Wellbore - Formation Temperature Distribution Under Circulating
Condition
The wellbore temperature after 1, 2, 4 and 8 h was calculated by using the data from the
example Wells, and the wellbore temperature distribution curve was drawn, as shown in
Fig. 3. As can be seen from the figure, there is an intersection point in the temperature
distribution curve. The lower well section below the intersection point is the formation
heat transfer to the wellbore, and the upper well section above the intersection point is
the wellbore heat transfer to the formation. This leads to a gradual increase in the upper
wellbore temperature and a gradual decrease in the lower wellbore temperature as the
G. Zhang et al.
3 Results Analysis
In order to analyze the variation law of CML dual-gradient drilling wellbore temperature
in the circulating process, the example well data in reference [16] for calculation. The
water depth of the well is 1500 m, the slurry level is located at 200 m below the sea
surface, the drilling fluid displacement is 30L/s, the geothermal gradient is 2.5 °C/100 m,
the mud inlet temperature is 25 °C, the sea surface temperature is 20 °C. The parameters
of well depth results and other basic parameters are shown in Table 1 and 2.
Table 1. Well depth structure parameters
String
type
Diameter/mm Length/m Depth/m
Drill
string
127.00
5000
0–3000
Marine
riser
533.40
1500
0–1500
Casing 273.05
3550
1500–4550
Naked
eye
215.90
50
4550–5000
Return
line
152.40
1000
0–1000
Table 2. Basic parameters
Thermophysical parameters
Sea
Drilling fluid
Cement
String
Rock
Conductivity
W /m · ◦ C
0.60
1.73
1.00
43.75
2.25
density
g/cm 3
1.03
1.50
1.90
7.80
2.64
Specific heat
J /g · ◦ C
4.18
3.94
2.00
6.40
0.84
3.1 Wellbore - Formation Temperature Distribution Under Circulating
Condition
The wellbore temperature after 1, 2, 4 and 8 h was calculated by using the data from the
example Wells, and the wellbore temperature distribution curve was drawn, as shown in
Fig. 3. As can be seen from the figure, there is an intersection point in the temperature
distribution curve. The lower well section below the intersection point is the formation
heat transfer to the wellbore, and the upper well section above the intersection point is
the wellbore heat transfer to the formation. This leads to a gradual increase in the upper
wellbore temperature and a gradual decrease in the lower wellbore temperature as the