We’ve learned so many topics regarding wait and weight well control method and I would like to share what advantages and disadvantages of wait and weight method are.
Advantages of Wait and Weight Method
• When compared to driller’s method, the wait and weight will generate lower pressure at casing shoe while circulating.
• It will generate the lowest pressure on surface equipment.
• It requires less circulation than driller’s method therefore time of equipment exposed to pressure is less.
Transocean demonstrates an excellent animated video of the Deepwater Horizon incident. This video will show you what was happened to the Deepwater Horizon rig’s BOP and there are a lot of things that you can learn from this VDO as sequence of the incident, deep water BOP stack configuration, why the BOP elements were failed, force of high flow velocity, etc.
Please click at the image below to see the full VDO.
Please give me your thought about this VDO.
Many topics of driller’s method have been taught on the drillingformulas.com and I would like to summarize about advantages and disadvantages of driller’s method.
• Circulation can be established right away so the bottom hole pressure will not increase much due to gas migration.
• Influx can be removed out of the well even though the rig does not have sufficient amount of weighting agent.
• Gas migration is minimized.
• Operation is quite simple when compared to weight and weight method.
• Calculation is simple and drill pipe pressure schedule is not required.
This section will show to how to use the formula from the previous topic, surge and swab pressure calculation 2nd method , to determine surge and swab pressure. I still use the same parameters as I used for the first method of surge and swab pressure calculation so you can compare the result between method#1 and method#2.
The well information is listed below:
θ300 = 85
θ600 = 130
Hole diameter = 9 inch
Drill Collar = 6.25 inch
ID of drill collar = 2.5 inch
Drillpipe diameter = 5 inch
ID of drill pipe = 3.5 inch
Average pipe running or pulling speed = 250 ft/min
Drill Pipe Length = 12000 ft
Drill Collar Length = 800 ft
Current Mud Weight = 12.5 ppg
Well TVD = 9000 ft
This is another method for calculating surge and swab pressure. With this method, there are 3 assumptions as follows:
• Closed ended pipe (plug flow)
• Laminar flow around drill pipe
• Turbulent flow around drill collar
How to determine surge and swab pressure with this method
1. Determine pressure around drill pipe
2. Determine pressure around drill collar
Note: The calculation methodology is different from the first method because both pressure losses are determined by separate set of equations.
3. Determine total pressure loss by summation of step 1 and step 2
4. Determine surge and swab pressure
1. Determine fluid velocity around drill pipe
Where;
Vdp is the fluid velocity around drill pipe in ft/min.
Vp is pipe movement velocity in ft/min.
Dp is drill pipe diameter in inch.
Dh is hole diameter in inch.
