Page 291 - Well Control for Completions and Interventions

284 Well Control for Completions and Interventions

pressure (with a safety factor), or the mechanical limit. If LCM is
needed, this is normally pumped ahead of the kill fluid.
5. Continually monitor pump pressure. Pump pressure is stepped down
as the tubing fills with kill weight fluid. Any reduction should be in
accordance with the planned pump schedule.
6. If pumping into a well with an isolated annulus, pressure must be
monitored. An initial increase caused by tubing ballooning should be
expected, but it should stabilize.
7. Once the required amount of fluid has been pumped (surface to reser-
voir volume), stop pumping and observe for pressure build-up or
losses. If LCM is pumped ahead of the kill fluid, anticipate a pressure
increase at the surface when the LCM reaches the formation
(Fig. 7.14 and Table 7.11).

7.4.4 Bullhead kill sheet example: vertical well
Kill sheet:
1. Calculate kill weight fluid required. Include 200 psi overbalance at top
of formation:

5500 1 200 = 10; 499 5 0:5429
Form pressure 1 overbalance
Top reservoir ðfeet TVDÞ Kill fluid gradient ðpsi=ft:Þ
0:5429 = 0:052 5 10:44
Kill fluid gradient ðpsi=ft:Þ Factor ðpsi=ft: to ppgÞ Kill fluid weight ðppgÞ
Round up:
10:44 Rounds up to 10:5

2. Calculate the maximum tubing pressure (formation fracture limit)—at
start of kill (tubing filled with oil and gas):
7534psi 2ð72230:1Þ1ðð6:530:052Þ3ð10;4992722ÞÞ
Tubing hydrostatic Pressure
Formation fracture pressure ðpsiÞ
5 4157psi
Formationlimit ðstartof killÞ

Formation fracture pressure is obtained by multiplying the fracture mud
weight equivalent (13.8 ppg) by 0.052 to obtain a fracture gradient
(0.7175 psi/ft.). The fracture gradient is then multiplied by the depth
(TVD) to obtain the formation fracture pressure.