In order to train the drill crew in the procedures that apply in connection with well control, or reinstatement of lost well control barriers, drills shall be conducted. The drills shall be conducted regularly, and initially very frequent to ensure that the drilling unit equipment and procedures are known to the crew, and that the crew remains alert to the implementation of the well control procedures that apply.
All crew members shall have pre-assigned tasks for each well control situation, appropriate to their function in the crew.
Well control drills shall be initiated by the Drilling Supervisor at unscheduled times when operations and hole conditions permit, and be reported by the Drilling Superintendent.
1. Diverter Drill
The diverter drill will be practised in order to train the crew with regards to shallow gas encountered during top hole drilling.
The response time here is critical, and in combination with the correct execution of operations the criteria for the assessment of the drill performance.
By manipulating the pit level sensors and/ or the flow sensor, a simulation of shallow gas influx shall be done while the drill string is still inside the 26" conductor, and prior to drilling out the shoe track. The crew should follow the following sequence of operations:
During drilling with drill pipe on bottom:
1. Recognise "kick" and alert crew.
2. Stop drilling and immediately start pumping drilling fluid at maximum rate.
3. Close the diverter, which automatically will initiate the following sequence:
- The diverter valve is opened.
- The flow line (mud return) valve is closed.
- The diverter element (annular preventer) is closed.
4. Prepare the switch-over to kill mud, and start mixing additional kill mud.
During tripping:
1. Recognise "kick" and alert crew.
2. Close the diverter.
3. Hang off the drill pipe in the slips, and stab the top drive on to the drill pipe again.
4. Start pumping kill mud at maximum rate.
2. Kick Drill While On Bottom
Below the top hole section of the well the following drill shall be applied.
Manipulate the pit level sensor, and/or the flow sensor to simulate a kick.
The crew shall perform the following tasks routinely to secure the well:
1.Recognise the 'kick' and alert the crew.
2.Pull the kelly or top drive above the rotary table until the lower kelly cock is above the drilling floor; at the same time slow down the pump.
3.Stop the pump.
4.Check for a flow.
5.Open the pressure-operated valve in the side outlet from the BOP stack to the choke manifold (the inner valve is always open under normal conditions).
6.Close in the well.
7.Take readings of the closed-in annulus and drillpipe pressures.
8.Measure the 'gain' in the active mud tank(s).
3. Kick Drill While Tripping
The drill is initiated by manipulating the trip tank level sensor.
The crew should perform the following tasks routinely to secure the well:
1.Recognise the 'kick' and alert the crew.
2.Lower the stand and install a lower kelly cock in open position.
3.Close the lower kelly cock, install a Gray-type inside BOP; open the lower kelly cock.
4.Open the pressure-operated valve in the side outlet from the BOP stack to the choke manifold.
5.Close in the well.
6.Make up the kelly, top drive, or the circulating head in the string.
7.Take readings of the closed-in annulus and drillpipe pressures.
8.Measure the 'gain' in the active mud tank(s).
4 Circulating-Out-A-Kick Drill
Prior to drilling out of the first intermediate casing on each well, the crew shall be trained in circulating out a kick.
5 Stripping Drill
After a BOP pressure test, prior to drilling out the shoetrack of a cemented casing, while tripping in, a stripping drill should be conducted.
Stripping is conducted for the purpose of running the drill pipe to bottom of the hole, prior to begin a well kill attempt. It is carried out against pressure, and the BOP must remain closed during the operation.
While running in the BHA, prior to the strip drill, mud should be circulated through the standpipe & choke manifolds, into and out of the poor boy degasser and down to the trip tank. This ensures firstly that the lines are clear and secondly that the degasser is sufficiently full for the correct volumes to be bled into the trip tank from the start of the drill. The correct operation of the vacuum breaker in the line from the poor boy degasser to the trip tank should also be checked.
Prior to the strip drill, perform a pre-job meeting with the drilling crew. This should explain the drill and what it intends to practice. Specific tasks for the drill should be allocated to each crew member by the person who will coordinate the drill (Drilling Contractor's Drilling Section Leader or Night Representative).
Then proceed as follows .
1. Install kelly cock and close same.
2. Close the annular preventer.
3. Install Gray-valve and open kelly cock.
4. Open choke line HCR valve. (Auto-choke should be closed already i.e. set up for Hard Shut-In). Close manual valve upstream of Auto-choke.
5. Open HCR on kill line and apply 30 bar to the annulus. Close the kill line HCR valve.
6. Reduce the closing pressure of the annular preventer to the minimum stable pressure achievable (approximately 28 bar = 400 psi.) Check for leakage through the annular. If leakage is evident, increase annular closing pressure to minimum to avoid leakage.
Line up returns from the choke manifold through the poor-boy degasser to the trip tank.
8. The trip tank should be filled to approximately 1/3 full at the start of the drill.
9. Make up the next stand. Check the tooljoint for sharp edges, lubricate with pipe dope.
10. Open manual valve upstream of the Auto-choke. Strip in one stand, maintaining Pann = 30 bar. The key to success is good communication between the driller and the person at the choke.
11. When the stand is stripped-in, close the choke, check Pann = 30 bar. Check that the volume increase in the trip tank, equates to the closed-end displacement of 1 stand of drillpipe. (e.g. 1 stand of S135 d.p. = 374 Litres). Drain the closed-end displacement volume form the TRIP tank into the STRIP tank. The crew member performing this task should use the marker plate, calibrated in stands, fitted inside the strip tank. Driller to check the volume drained from the trip tank via the SiDrill monitoring system and mudloggers.
12. Repeat steps 9 to through 11 for some four times.
13. At the end of the drill, open the HCR valve on the kill line (to prevent pressure being trapped behind the check valve), bleed off all casing pressure. Close choke - and kill line HCR valves.
14. Pull the stripped-in stands. Remove Gray valve (depress plunger first to check for trapped pressure) and kelly cock. Return choke manifold line-up to that for Hard Shut-In.
Notes:
- "Stripping checklists" should be available on the drilling unit and used during the drill.
- During the strip drill fill up every stand to prevent collapsing.
6 Reporting
The following shall be recorded by the Drilling Supervisor, or his representative, monitoring the drill:
- the reaction time from the moment the kick is simulated until the designated crew member is ready to implement the well control procedure,
- the total time it takes to complete the entire drill.
Based on this the Drilling Supervisor shall judge the performance of the crew, and the equipment, to evaluate the need for further training and improvement.
7 Reaction times
The following shall be recorded in the tour report and the morning report:
- the reaction time from the moment the kick is simulated until the designated crew member is ready to start the closing procedure;
- the total time it takes to complete the entire drill.
The Company drilling representative will then be in a position to judge the performance of the crew and the equipment, and to take the necessary steps for improvement.
Experience has indicated that well trained crews can perform well control drills in 3 to 4 minutes. Drills shall be carried out to achieve and maintain this performance standard.