Page 302 - Well Control for Completions and Interventions

Well Kill, Kick Detection, and Well Shut-In 295

3: Calculate expected Δp
SITHP
1: Pump

4: Bleed

2: Wait for gas
Migration: fluid
To fall

Figure 7.18 Pump wait calculate bleed. The four basic steps for a lubricate-and-
bleed well kill.

pressure repeatedly and quickly builds up after bleed-off. Three different
lubricate-and-bleed methods are described here. In each, the fundamental
principle is the same; fluid is pumped in at the surface and allowed to
drop down the well, through the gas column. Gas pressure, equivalent to
the hydrostatic head of the fluid pumped, is bled-off. The cycle of pump
(lubricate) then bleed is repeated until the well is dead (Fig. 7.18).
As with the circulating kill, setting a mechanical plug close to the
bottom of the well can be beneficial during a lubricate-and-bleed.
Providing the plug maintains integrity, it will prevent losses to the forma-
tion. It will also prevent a second influx if the person operating the choke
is too aggressive and allows BHP (at the plug) to drop below reservoir
pressure. Although the presence of a plug undoubtedly aids the kill
process, maintaining BHP above reservoir pressure is still recommended.

7.7.1 The constant volume method (lubricate and bleed)

The constant volume method is so called because the volume pumped at
each lubricate and bleed cycle is the same, and therefore the hydrostatic
pressure reduction should be approximately the same for each cycle (in a
vertical well). Kill fluid is accurately measured (from a calibrated tank)
before pumping, and bleed-off calculations are based on the hydrostatic
pressure reduction of that measured volume. As the fluid is pumped into