General Questions With Answers - 5 -

1. What is "Chip Hold Down "pressure? How does this affect penetration rate?

2. Happily drilling an 8.1/2" hole at 12200 ft with a 0.6 psi/ft mud. The well starts to flow. Outline the step by step procedure for shutting in the well.

3. In the same well above Pdp = 500psi and Pann = 620psi. While mixing the kill mud (30 minutes) Pdp rises to 600 psi and Pann rises to 720 psi.

a. Explain what has happened.
b. What do you undersand by the term primary and secondary build up.
c. Outline the step by step procedure for starting to kill the well and establishing the correct Standpipe pressure.

4. After drillling to 13000 ft a gas sand is penetrated and it is decided to pull out for coring. The brake cooling system fails on the trip out and it is decided to stop at the 9.5/8" casing shoe and carry out repairs.

a. What are the precautions that you would take to safe guard the well during the period that the cooling system is being repaired.
b. It takes 5 hours to finish the repairs. Outline the procedure that you would take until the bit reaches surface.

5. Why do we drill top hole ( 17.1/2") with a reduced ROP :

a. better determination of formation tops.
c. to keep the mud weight low.
d. lower torque.
e. because we always do it.
f. to prevent swabbing.
g. to prevent gas cut mud.

6.  Poor-Boy Mud/Gas Separator

a. Which one of the poor-boy mud gas separator dimensions limits the capacity of the seperator before gas blow through occurs?

b. Which of the dimensions of the same mud/gas separator determines the presure build up in the separator?

c. What is the maximum that the pressure gauge could read before the mud seal is lost in the separator? Assume that the mud weight in use is 12.5 ppg.

d. What aspect of your killing procedure would you consider for controlling pressures that may be encountered in the poor boy mud/ gas separator?

dimensions are ;

D1 = 8"      D2 = 6"           D3 = 48"        L1 = 140"         L2 = 20"       L3 = 8''       L4 = 10''


1. When the bottom hole pressure BHP of the fluid column is greater than the formation pore pressure, the bit tooth will have to overcome this pressure to push the chip out. 
The smaller the difference between the BHP and the pore pressure, the easier/faster the bit will drill.

2. Space out (almost tool joint 1 m above the rotary table), Stop pumps, close one preventer ( Annular or pipe rams), open HCR, note down drill pipe pressure (Pdp) and casig pressure (Pann)

3. a) The gas is migrating up to surface.(Without expanding)

b) Primary build-up is the initial pressure build-up showing an indication of the Permeability of the reservoir. Secondary build up is when both Pdp and Pann are going up at the same rate, showing the migration speed of the gas in the well.

c) Start pumps by keeping Annular pressure Pann constante until the correct kill pump speed is obtained, then keep drill pipe pressure Pdp constante by opening or closing the choke till evacuating the gas out of the hole.

4. Line the well up on the trip tank and keep the trip tank pump running. Keep watch on trip tank level. I would run back to bottom and circulate bottoms-up to ensure no problems.

5. a) Length L3 
    b) D1 and L1
    c) 12.5*0.052*8(L3)= 5.2 psi 
    d) The kill pump speed.

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