CPA Well Control & Blowout Prevention 2 — Questions and Answers
Question 1: Which type of BOP ram can close and seal the wellbore around any size of drill pipe or even on an open hole?
- Pipe ram
- Blind ram
- Annular preventer (Spherical BOP) (Correct answer)
- Shear ram
Correct answer: Annular preventer (Spherical BOP)
The annular preventer (also called a spherical BOP) uses a donut-shaped rubber packing element that can seal around any size of drill pipe, kelly, or open hole by compressing inward.
Question 2: What is the 'kill line' on a BOP stack used for?
- To circulate heavy mud into the wellbore from the surface to kill the well (Correct answer)
- To monitor annular pressure during well kill operations
- To vent gas safely away from the rig during a blowout
- To inject chemical inhibitors into the casing annulus
Correct answer: To circulate heavy mud into the wellbore from the surface to kill the well
The kill line connects the mud pumps to the BOP stack below the pipe rams, allowing heavy kill-weight mud to be pumped into the wellbore to overcome formation pressure and kill the well.
Question 3: What does Shut-In Drill Pipe Pressure (SIDPP) indicate?
- The maximum allowable casing pressure before formation breakdown
- The formation pore pressure minus the hydrostatic pressure of the mud in the drill string (Correct answer)
- The pressure required to circulate mud at normal drilling rates
- The tensile load on the drill pipe at the surface
Correct answer: The formation pore pressure minus the hydrostatic pressure of the mud in the drill string
SIDPP represents the difference between formation pore pressure and the hydrostatic pressure of the mud inside the drill string, and is used to calculate the kill mud weight needed.
Question 4: What is the primary function of the choke manifold in well control operations?
- To divert drilling returns away from the shale shakers during normal drilling
- To control annular back pressure while circulating a kick out of the well (Correct answer)
- To regulate mud pump pressure during normal drilling operations
- To mix weighting material into the drilling fluid system
Correct answer: To control annular back pressure while circulating a kick out of the well
The choke manifold allows the driller to maintain back pressure on the annulus while circulating a kick out, preventing additional formation fluid influx while keeping the bottom hole pressure constant.
Question 5: What does 'gas-cut mud' returning at surface indicate?
- The drill bit is worn and needs replacement
- Formation gas has contaminated the drilling fluid, reducing its density (Correct answer)
- The mud pump liners need to be replaced
- Surface equipment is introducing air into the mud system
Correct answer: Formation gas has contaminated the drilling fluid, reducing its density
Gas-cut mud occurs when formation gas enters the drilling fluid and becomes entrained in it, significantly reducing the mud density and potentially leading to reduced bottom hole pressure and a kick.
Question 6: What is the purpose of a float valve (check valve) installed in the drill string?
- To prevent mud from being lost to the formation during drilling
- To prevent formation fluids from flowing up through the inside of the drill string (Correct answer)
- To regulate flow distribution between drill collars and drill pipe
- To maintain constant weight on bit regardless of heave on offshore rigs
Correct answer: To prevent formation fluids from flowing up through the inside of the drill string
A float valve is a one-way check valve in the drill string that allows mud to be pumped downward but prevents backflow of formation fluids up through the drill string interior.
Question 7: What is 'Shut-In Casing Pressure' (SICP) used to determine during a well kick?
- The minimum mud weight needed to safely drill ahead
- The pressure and composition of the formation fluid that has entered the wellbore (Correct answer)
- The maximum allowable wellhead pressure before the formation fractures
- The volume of kill mud required to displace the kick fluid
Correct answer: The pressure and composition of the formation fluid that has entered the wellbore
SICP, measured at the casing side after shut-in, helps determine the nature and density of the kick fluid (gas is lighter and gives higher SICP relative to SIDPP, while saltwater gives nearly equal pressures).
CPA Well Control & Blowout Prevention 2
Which type of BOP ram can close and seal the wellbore around any size of drill pipe or even on an open hole?