Advanced MACP/MAASP Well control concepts
Kanwal Panaich
Well Control Fundamentals
October 3, 2016
Maximum allowable Casing Pressure: MAASP/MACP vs. Gassed out annulus
Leak-Off test is performed below the last casing shoe in the Oil or Gas well to test the maximum pressure that can be applied to the few meters of bare rock without losses into the open hole.
• Leak-Off Pressure = HPTest mud density + Surface Applied Pressure Deviation point on graph
• Leak-Off Pressure = HP Drilling mud density + Maximum Allowable Casing Pressure Kill sheet
• Leak-Off Pressure – HPDMD/GAS = MACP/MAASP
Once the Leak-Off Test benchmarks the shoe strength for a given pressure which can’t be exceeded. The Leak-Off Pressure is relevant to the rock strength below the true vertical depth of the last casing shoe which is non-changing number, only change which happens in the well bore is Hydrostatic Pressure. What happens to the HP when the test mud is changed to Drilling Mud/Gassed out casing annulus/Kill mud density?
Why are the following parameters must be taken note of:-
• How long the Well was SHUT IN vs. Migration rate of Gas?
• Cased hole Annulus Volume vs. PVT Gain?
• Open Hole Volume vs. Strokes pumped?
MACP vs. HP GASSED OUT ANNULUS / TEST MUD / DRILLING /KILL MUD
Drilling/WC Events Leak-Off Pressure HP MACP/MAASP
Leak-Off Test Bench Marked Test Mud Density Surface applied Pres.
Drilling Ahead Stays the Same Press. WBM/ HP=? MACP= Inc./Dec.?
Drilling Ahead
Circulating the Gas out/Annulus full of Gas Stays Same
Stays Same Invert Mud/HP= Up/Down?
HP with gas=Up/Down? MACP= Inc./Dec.?
MACP= Inc. /Dec.? Is it OK to exceed MACP with exceeding 80% of casing burst pressure?
How to know where the gas is and what’s the volume of the gas:
• Migration rate of the gas and how long we are shut-in should help us in approximating the Bubble location i.e. below the shoe or above the shoe.
• Please also take note of your Pit Gain, Open-Hole strokes and cased hole Volume. If the bubble has been circulated above the casing shoe and PVT gain is more than the Cased Hole Annulus Volume, then we can reasonable assume that the casing annulus is full of gas. We should calculate the Hydrostatic Pressure with gas gradient, since HP of gas is less vs. HP with drilling mud therefore MACP should expand by the reduction in HP from mud to gas.
• Is it OK to exceed the calculated MACP? What is 80% of casing Burst Pressure?
• Please feel free to discuss the concept further till it sinks in. If understood right may save a Life, RIG, Well & the environment
