Bidvertiser

Loading...

HOW TO KILL A WELL

If an indication of a kick has been observed and a flow check has been confirmed, the well must be shut in as  soon as it is in a safe condition. It is now possible to kill the well.
The objective of the kill procedure are in two fold. One is to circulate out any fluid which has invaded the well during the
kick. The other is to circulate into the well a satisfactory weight of kill mud. This should be done without allowing any further influx and with minimum damage to the well.

SHUTTING THE WELL IN
Imagine that drilling is in progress. The rotary table would be turning. The mud pumps running. There would be weight on the bit and the driller would be making a hole. At certain point in these operation an increase in mud returns is observed. This is an indication of a possible kick.




PROCEDURES INVOLVED IN SHUTTING A WELL

  • Stop the rotary
  • Raise the kelly until a tool joint is above the rotary
  • Stop the pumps
  • Check for a flow.
  • If positive, open choke line valve at the BOP stack
  • Close the choke

Following the above procedure makes the well safe, with pressures locked in the well. These pressures should be recorded and a note made of the pit volume gain. The rig supervisors should be alerted at this time.

KILLING THE WELL
When the well has been shut in, everyhting will be static. The well pressure will be balanced.  In the drill pipe, is a column of mud know as as density (weight). In the annulus is a mixture of mud and formation fluids which have invaded the hole , the kick. The annulus is shut off at the surface by the BOP and of course the drill string is blocked off by the pumps which are stopped.
In order that the correct weight of kill mud can be calculated, the formation pressure which caused the kick must be determined.

When the well was closed the formation pressure was greater than the pressure being exerted by the drilling fluid. That was why the kick occurred. In the order for the pressure to be balance, there would be an increase in pressure at the surface on both the drill pipe and the annulus. These two pressures are usually referred to as the shut in casing pressure (SICP).

The pressure would not be the same, As you will see , the SICP is greater than SIDPP.
The hydrostatic pressure exerted by the column of mud. Plus the hydrostatic pressure exerted by the column of the influx. Plus the pressure at the surface , the SICP.

However, the drill pipe side is full of mud of known density. This information together with the depth of the well and the SIDPP can be used to calculate the formation pressure.
FORMATION PRESSURE= HYDRO STATIC PRESSURE+SIDPP PRESSURE OF MUD IN THE

DRILL PIPE
Once the formation pressure is known, the mud weight required to balance it can be calculated. The formation pressure is divided by the depth of the well would give a pressure gradient for a fluid which would just balance the formation  pressure .

The gradient can be converted to a mud weight by dividing by 0.052 (or multiply by 1/0.052).

KILL MUD WEIGHT= (FORMATION PRESSURE(PSI)/TRUE VERTICAL DEPTH(FT)) x 1/0.052

ENGINEERING 6448118492500484236

Post a Comment

emo-but-icon

Home item

Bidvertiser

MOST RECENT POSTS