TM6004

TEKNIK PEMBORAN LANJUT

Exercise 4 – Well Killing Technique

Well control

Oleh

PRADINI RAHALINTAR

NIM: 22214003

(Program Studi Magister Teknik Perminyakan)

INSTITUT TEKNOLOGI BANDUNG

2015

Exercise 4 Well Killing Technique

1. Briefly explain the essential differences between the "one circulation method" and the

"driller’s method" for killing a well.

Basically “one circulation method” or wait and weight (WW) method and Driller`s method

(DM) have the same principle, the way the kick is circulated out of the well are performed in

the same way, the choke is used to control and maintain a constant bottom hole pressure and

the goal is to re-establish the primary well barrier. But the main difference between the two,

that is when kill mud is introduced to the circulation process. For DM a whole annulus

circulation is performed before kill mud goes into the circulation flow. In this method the influx

is first of all removed with the original mud. Then the well is displaced to heavier mud during

a second circulation. In this driller`s method there are always a constant fluid column either in

drill string or in annulus. Whereas “one circulation method” or WW method weighted kill mud

is added simultaneously as the kill circulation process starts. The kill mud is introduced at once

in the circulation process with the intention to re-establish the well barrier. This will, compared

to DM, reduce the process time. The one circulation method is generally considered better than

the Drillers method since it is safer, simpler and quicker.

2. Briefly explain how and why the wellbore pressure is monitored and controlled

throughout the well killing operation (assuming that the "one circulation method" is

being used to kill the well).

Why wellbore pressure is monitored and controlled throughout the well killing operation is

because we have to make sure that the well is in equilibrium and there is no increase in the

surface pressures the wellbore pressure must be equal to the formation pore pressure so there

will be no additional kick fluid entering the wellbore. If it becomes lower than formation

pressure then there will be additional kick fluid and if it is higher up until formation fracture

pressure then the well will be fractured.

The main principle of “the one circulation” method is that bottom hole pressure, Pbh is

maintained at a level greater than the formation pressure throughout the operation, so that no

further influx occurs. This is achieved by adjusting the choke, to keep the standpipe pressure

on a planned profile, whilst circulating the required mud-weight into the well. A worksheet

may be used to carry out the calculations in an orderly fashion, and provide the required

standpipe pressure profile. While the choke is being adjusted the operator must be able to see

the standpipe pressure gauge, and the annulus pressure gauge.

The drill-pipe and annulus pressures will be different since, when the influx occurs and the

well is shut-in, the drill-pipe will contain drilling fluid, but the annulus will now contain both

drilling fluid and the fluid (oil, gas or water) which has flowed into the well. Hence the

hydrostatic pressure of the fluids in the drillstring and the annulus will be different. The

increase of hydrostatic pressure should be balanced by decreasing the surface pressure. By the

time the heavy mud reaches the bit the initial shut-in pressure,Pdp should be reduced to zero

psi. The standpipe pressure should then be equal to the pressure drop due to circulating the

heavier mud.