SECTION 10
KILL OFFSHORE KICK QUICKLY
Practical procedures for killing a kick on an offshore platform or a jack-up rig are much the same as on land. The basic difference is that the holes are larger and the pressures tend to occur at a shallower depth. This causes the casing pressures to be lower.
This problem shows how to develop the information needed to kill a kick in a minimum amount of time when very little information is available.
Key points. Notice how low the casing pressure remains in the problem. This is the effect of the large hole. Of course, with a very big kick, casing pressure would be higher. However, in offshore drilling, you generally will lose the well (lost circulation) if you have a very big kick.
In deep water, the column of mud from the sea floor to the flow line works against you so that as you get in deeper water, the kick must be kept smaller or you will lose the hole.
The kick occurs in this problem at 8250 ft (2500 m). In areas of more recent sediments offshore, you can expect gas pressures at shallower depths.
PROBLEM 10
Problem 10-0:
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Problem facts:
You were flown out to the mobile rig, Jackup, to kill this kick as quickly as possible. Everyone is in a panic. This is all you know:
Depth = 8250 ft (2515 m)
Hole size = 15" with 5" drill pipe
Mud density = 9.6 ppg (1,15 sg, 72 lb/ft3)
Drilling program requires trip margin to be 0.5 ppg (0.06 SG, 4lb/ft3).
Surface-to-bit pump strokes = 560
Kick size: "Not very much" says the tool pusher -"Bigger than hell" says the derrickman.
Fill out as much of the pressure control work sheet as you can before you start.
Problem 10-1:
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You decide to use 40 spm as a pump rate while killing the well. The mud weight is being increased as quickly as possible. When you started circulating the mud density in the suction pit was 9.6 ppg (1.15 SG, 72lb/ft3).
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase the pump rate?
4 Decrease the pump rate?
5 Everything is OK-continue?
6 Stop the pump and close the well in?
Problem 10-2:
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Now, quickly finish the pressure control work sheet. Don't try to keep it all in your head. You can do that on this problem, but the penalty on the rig if you forget is too high.
Problem 10-3
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At 600 pump strokes the mud density was 10 ppg (1.2 SG, 75 lb/ft3). At 800 pump strokes the mud density was 10.5 ppg (1.26 SG, 78 lb/ft3) in the suction pit.
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase the pump rate?
4 Decrease the pump rate?
5 Everything is OK-continue?
6 Stop the pump and close the well in?
Problem 10-4
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The bulk hopper line is plugged and the crew is mixing the weight material from sacks. At 1200 pump strokes, the mud density was 11 ppg (1.3 SG, 82 lb/ft3).
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase the pump rate?
4 Decrease the pump rate?
5 Everything is OK-continue?
6 Stop the pump and close the well in?
Problem 10-5
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Have you lost track of things by trying to weight up the mud while circulating? The annulus pressure gauge is just drifting lower - it must be broken.
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase the pump rate?
4 Decrease the pump rate?
5 Everything is OK-continue?
6 Stop the pump and close the well in?
Problem 10-6
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Mud density is 11.4 ppg (1.37 SG, 85 lb/ft3) at the suction. You can't guess-you have to be sure. The wave height is 15 ft (5 m) and increasing, and the weather report says you are in for a storm. Do you have enough barite on board?
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase the pump rate?
4 Decrease the pump rate?
5 Everything is OK-continue?
6 Stop the pump and close the well in?
Problem 10-7
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You can't read the drillpipe pressure or pump rate because the gauge needles are moving too much. The kelly hose is trying to jump out of the derrick. You still have light mud coming out of the choke separator line and you have not seen any gas or salt water yet.
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase the pump rate?
4 Decrease the pump rate?
5 Everything is OK-continue?
6 Stop the pump and close the well in?
Problem 10-8
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The tool pusher is worried about the #2 pump. He wants to keep the pressure as low as possible. It may have a bad swab. Both #1 and #2 pumps are the same size.
What should you do:
1 Wait until #1 pump is repaired?
2 Use #2 pump at 20 spm?
3 Increase the mud density?
4 Call the shore base?
5 Call the standby boat?
Problem 10-9:
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The tool pusher agreed to 20 spm on #2 pump. You made the shutdown and changeover in about 5 min. You hold annulus pressure constant while bring pump speed up to 20 spm, but look how low the drillpipe pressure is!
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase the pump rate?
4 Decrease the pump rate?
5 Everything is OK-continue?
6 Stop the pump and close the well in?
Problem 10-10:
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#1 pump had a bad swab and it took about 1 hour to change it. The driller says #1 pump is ready to go. There is some gas at the choke and annulus pressure is surging.
What should you do:
1 Increase choke size?
2 Decrease choke size?
3 Increase the pump rate?
4 Decrease the pump rate?
5 Everything is OK-continue?
6 Stop the pump and close the well in?
Problem 10-11:
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You have pumped the gas out of the well. The mud density at the choke/separator is 11.4 ppg (1.37 SG, 85 lb/ft3). You shut off the pump. The well does not flow. Can you make a short trip now or must you increase the mud density and circulate some more.
What should you do
1 Increase the mud density?
2 Increase the mud density and circulate?
3 Continue to circulate?
4 Everything is OK. Make the short trip.
5 Call for more barite.
ANSWERS
Problem 10-0: See pressure control work sheet Figure 10-1.
Problem 10-1: Everything is OK - continue. Now you are ready to switch over to drillpipe pressure.
Problem 10-2: See pressure control work sheet Figure 10-2.
Problem 10-3: Everything is OK - continue. If you had completed you pressure control work sheet using mud density and pump strokes on the graphical analysis, you could see that drillpipe pressure should be 1850 psi (130 kg/cm²).
Problem 10-4: Increase the choke size. You cannot make the mistake of assuming that casing pressure stays constant. You must follow your graphical analysis. Drillpipe pressure should be about 1650 psi (116 kg/cm²).
Problem 10-5: Increase the choke size. Follow your graphical analysis. There is no way to use annulus pressure in this technique because you don't know where the gas is in the annulus.
Problem 10-6: Everything is OK. Look at the drillpipe pressure on the pressure control work sheet. Annulus pressure is going down because of the heavier mud in the annulus.
With seas increasing, it is very important to get the heavy mud in the hole as soon as possible. However, if you increase the pump rate, you may have trouble adding the proper amount of barite to the mud. You should have known how much barite it would take to increase the mud density.
Problem 10-7: Stop the pump and close the well in. Then we will switch to the #2 pump. There is something wrong with the #1 pump.
Problem 10-8: The best answer is 2 - Use the #2 pump at 20 spm. Use of 20 spm will reduce the pressure on #2 pump. If it goes out you can always shut in again. The gas is almost to the surface and we should get it out of the hole as quickly as possible.
You could use answer 1 - wait until #1 is repaired. If you do, be sure to bleed off the annulus pressure so to keep the drillpipe pressure zero. This has hazards and you may lose the hole.
Remember seas are increasing and you want to get the heavy mud in the hole as soon as possible.
Problem 10-9: Everything is OK. Your technique of holding annulus pressure constant while starting the pump is OK. The #2 pump is the same as the #1 pump and going only half as fast. You can expect the circulating pressure to be much lower.
Remember two things:
first, you can stop the pump and shut the well in at any time.
Secondly, holding annulus pressure constant is a "make-do" method, so keep it constant for as short a period as possible.
Problem 10-10: Everything is OK - continue. You do not want to change pumps when the gas is near the surface, and the annulus pressure is surging. Get the gas out of the hole before changing pumps. You could use the original FCP 1580 psi (112 kg/cm²) at 40 spm for #1 pump but it is better not to shut in at this point.
Problem 10-11: Everything is OK. You can make the short trip. Remember, you have already added 0.5 ppg (0.06 SG, 4lb/ft3) overbalance to the original calculations.
To avoid confusion always keep a pressure control work sheet, a record of pump strokes and pressures.
However, since a storm is coming, 3 - continue to circulate - may be a better answer.
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