Page 503 - Air and Gas Drilling Manual

10-28 Air and Gas Drilling Manual
2
V
Tee
K
∋ P
2
K
Tee
v
Tee
Tee
g
2
where K Tee is the minor loss flow resistance coefficient for the Tee,
K v is the minor loss flow resistance coefficient for a valve.
Using the dimensions of the Tee, Figure 8-5 can be used to obtain the approximate
minor loss resistance coefficient of the Tee. This is
K Tee 27
The approximate minor loss resistance coefficient for the valve is [12]
.
K v 02
Substituting the values of Tee, K Tee, K v, V Tee, and g into the above equation gives
63 02 2
.
.
∋ P 1 597 27 2 0 2
.
Tee
232 2
.
2
,
.
∋ P Tee 2 698 7 lb/ft
The pressure upstream of the Tee at the top of the annulus, P Tee, is
P P ∋ P
Tee sr Tee
P Tee 4 604 4 2 698 7
,
.
,
.
2
,
.
P Tee 7 303 1 lb/ft abs
p Tee P Tee 144
.
p Tee 50 7 psia
Geometry in the Annulus
Major and minor friction losses must be included in order to obtain accurate
bottomhole and injection pressures. Therefore, it is necessary to include the
geometric dimensions of the drill pipe tool joints. When drilling at 10,000 ft, the
drill string is composed of 9,500 ft of API 4 1/2 inch, 16.60 lb/ft nominal, EU-
S135, NC50 (IF) from the surface to the top of the drill collars. The 4 1/2 inch
outside diameter body of the drill pipe has an inside diameter of 3.826 inches (see
Table B-3). Approximately every 30 ft there are tool joints which are about 1 1/2 ft
in length. The outside diameter of these tool joints is 6 5/8 inches with an inside
diameter of 3 1/2 inches. For the calculations that follow, the drill pipe tool joint