Page 259 - Well Control for Completions and Interventions

Well Kill, Kick Detection, and Well Shut-In 253

3. Calculate the surface pressure at the critical points in the kill, and plot
a kill graph for tubing and annulus pressure. A 200 psi overbalance is
required during and after the kill.

7.3.8.1 Calculate the gradient of kill weight fluid required
to overbalance well pressure by 200 psi
Since the well is plugged, it must be killed to the SSD at 10,300 ft., and not
the reservoir. This ensures the overbalance is maintained if the plug leaks.
Average gradient (psi/ft) of tubing fluid is given (Table 7.2 and Fig. 7.1)
or can be calculated from:
ðreservoir pressure SITPÞ 4 reservoir depth
ð5570 2 1900Þ 4 10; 500 5 0:3495 psi=ft-0:35 psi=ft

Tubing pressure at the SSD: SITP 1 (tubing fluid gradient 3 depth
at SSD)

1900 1 ð0:3495 3 10; 300Þ 5 5500 psi:
Fluid density (PPG) needed to hold 200 psi overbalance at the SSD is:

ðpressure at circulating port 1 overbalanceÞ
4 ðdepth of circulating port 3 0:052Þ

ð5500 1 200Þ 4 ð10; 300 3 0:052Þ 5 10:64: By convention; kill weight is
always rounded up:

10:64-10:7 10:7 ppg 3 0:052 5 0:5564 psi=ft:

Table 7.2 Reverse circulation kill data

Top reservoir depth 10,500 ft.
Reservoir pressure (P r ) 5570 psi
Plug depth 10,350 ft.
Packer depth 10,330 ft.
Sliding sleeve or sliding side door (SSD) depth 10,300 ft.
1
5/2 in 23 lb/ft tubing ID 4.670 in.
9/8 in 53.5 lb/ft casing ID 8.535 in.
5
SITP 1900 psi
SICP 0 psi (before sleeve open)
Packer fluid gradient 0.52 psi/ft. (10 ppg)
Oil gradient 0.35 psi/ft. (6.73 ppg)
Planned overbalance 200 psi