The detection of a kick when the drill collars are in the BOP stack is a time of concern for the safety of the crew and the drilling unit as the normal methods of secondary control using the BOP’s may fail.
A kick of this nature can occur when the drill siring is being pulled out of the hole and is extremely hazardous for the following reasons:
- the kick is probably due to swabbing or a failure to keep the hole full.
- The force exerted by the wellbore pressure may exceed the weight of the drill collars.
- The late detection of the kick could indicate that the influx is close to the surface.
- In many cases there is no float valve in the string and it is difficult to install a full opening safety valve.
When the kick has been detected, the Driller must quickly decide whether to
- close in the well and strip to bottom
- or as a last resort, to drop the drill collars.
- Unless everything is readily available and the crew is well trained then it may be necessary to drop the drill collars and shut the well in with the blind/shear rams.
Shut-in Procedure with Surface BOP’s
If the well kicks while the drill collars are in the BOP the following procedure should be followed:
1. POSITION the drill collars at the rig floor and SET the slips.
Note: When the string is out of hole the drill collars should be racked in such a way that the drill pipe can be run in the hole first. Access to the stand with the drill pipe to drill collar x-over should be maintained at all times.
2. INSTALL the appropriate cross-over.
3. PICK UP a joint or a stand of drill pipe, MAKE-UP and RUN joint or stand into the hole.
4. MAKE UP full opening safety valve and CLOSE. CLOSE the annular preventer.
5. OPEN the hydraulic remote controlled valve and READ and RECORD pressures and pit gain.
6. INSTALL an inside BOP above the safety valve.
The string can now be stripped to bottom if necessary. If it is necessary to control the well at the present depth then provision should be made to secure the drill pipe to the rotary table with chains.
Dropping the Drill Collars
A quick decision may have to be made by the Driller to drop the drill collars The success of this last resort method depends on the severity of the kick and quick implementation of the correct procedure.
One procedure for dropping the drill collars is as follows:
- Position the elevators near the floor
- Close the annular preventer such that the elevators can be opened
- Open the annular preventer to drop the drill collars (BE PREPARED FOR A LARGE RECOIL WHEN THE DRILL COLLARS ARE DROPPED).
- Close the blind or blind/shear rams. Read and record shut-in pressure and pit gain.