CMM Exploration & Production Processes 2 — Questions and Answers
Question 1: Which drilling fluid system is most commonly used in shale formations to prevent wellbore instability?
- Water-based mud with potassium chloride
- Oil-based mud or synthetic-based mud (Correct answer)
- Air or foam drilling
- Clear brine fluids
Correct answer: Oil-based mud or synthetic-based mud
Oil-based or synthetic-based muds inhibit clay swelling and maintain shale stability better than water-based systems.
Question 2: What is the primary purpose of a casing shoe test (LOT/FIT) conducted after drilling out new casing?
- To verify cement bond quality
- To determine formation fracture gradient at the casing shoe (Correct answer)
- To measure wellbore deviation
- To evaluate formation permeability
Correct answer: To determine formation fracture gradient at the casing shoe
The Leak-Off Test establishes the maximum mud weight window and verifies the formation can support planned drilling pressures.
Question 3: In reservoir engineering, what does the term 'skin factor' indicate when it is a positive number?
- Enhanced well productivity due to stimulation
- Damage near the wellbore reducing flow capacity (Correct answer)
- High reservoir permeability
- Optimal completion design
Correct answer: Damage near the wellbore reducing flow capacity
A positive skin factor indicates near-wellbore damage (e.g., from mud filtrate invasion or scale) that restricts flow.
Question 4: Which seismic attribute is most useful for directly detecting hydrocarbons by identifying amplitude anomalies?
- Instantaneous frequency
- Amplitude versus offset (AVO) (Correct answer)
- Coherence/similarity
- Acoustic impedance inversion
Correct answer: Amplitude versus offset (AVO)
AVO analysis exploits how seismic amplitude changes with source-receiver offset to identify gas-charged or fluid-saturated sands.
Question 5: What is the main advantage of horizontal drilling compared to vertical drilling in tight or shale reservoirs?
- Lower drilling cost per well
- Greater reservoir contact length enabling economic production (Correct answer)
- Simpler wellbore completion design
- Reduced environmental surface footprint only
Correct answer: Greater reservoir contact length enabling economic production
Horizontal laterals expose hundreds to thousands of feet of pay zone, dramatically increasing drainage area and production rates.
Question 6: Which well control method involves closing the blowout preventers and circulating out a kick while maintaining bottom-hole pressure constant?
- Driller's method (two-circulation)
- Wait-and-weight method (engineer's method) (Correct answer)
- Volumetric method
- Bullheading method
Correct answer: Wait-and-weight method (engineer's method)
The Wait-and-Weight (Engineer's) method weights mud to kill weight in one circulation, maintaining constant bottom-hole pressure.
Question 7: In production logging, what does a spinner flowmeter primarily measure?
- Formation pressure at multiple depths
- Fluid velocity or flow rate in the wellbore (Correct answer)
- Cement bond quality behind casing
- Water saturation in the formation
Correct answer: Fluid velocity or flow rate in the wellbore
A spinner flowmeter measures the rate and direction of fluid flow inside the wellbore by recording spinner rotation speed.
CMM Exploration & Production Processes 2
Which drilling fluid system is most commonly used in shale formations to prevent wellbore instability?