CMM Exploration & Production Processes 3 — Questions and Answers
Question 1: What is the purpose of perforating a cased wellbore during completion operations?
- To set production packers
- To create channels through casing and cement into the formation (Correct answer)
- To clean drilling fluid from the near-wellbore area
- To measure formation temperature
Correct answer: To create channels through casing and cement into the formation
Perforating punches holes through the casing, cement, and into the formation to establish a flow path for hydrocarbons.
Question 2: Which secondary recovery method involves injecting water into a reservoir to maintain pressure and displace oil toward producing wells?
- Gas cycling
- Waterflooding (Correct answer)
- Steam injection
- CO2 miscible flooding
Correct answer: Waterflooding
Waterflooding is the most widely used secondary recovery technique, using injected water to sweep oil toward producers.
Question 3: What does the 'gas-oil ratio' (GOR) trend over time in a solution-gas-drive reservoir typically indicate?
- GOR decreases steadily as reservoir pressure drops
- GOR rises sharply as reservoir pressure falls below bubble point (Correct answer)
- GOR remains constant throughout field life
- GOR decreases as gas comes out of solution
Correct answer: GOR rises sharply as reservoir pressure falls below bubble point
Below the bubble point, free gas expands rapidly relative to oil, causing GOR to increase significantly.
Question 4: Which wireline log is primarily used to identify lithology and clay content by measuring natural radioactivity?
- Density log
- Gamma ray log (Correct answer)
- Neutron log
- Resistivity log
Correct answer: Gamma ray log
The gamma ray log measures natural radioactivity from potassium, uranium, and thorium, with shales showing high values and clean sands showing low values.
Question 5: In hydraulic fracturing, what is the role of the proppant material injected with fracturing fluid?
- To dissolve formation damage near the wellbore
- To keep induced fractures open after pressure is released (Correct answer)
- To reduce fluid viscosity during pumping
- To detect fracture height using radioactive tagging only
Correct answer: To keep induced fractures open after pressure is released
Proppant (typically sand or ceramic beads) props open hydraulic fractures after pump pressure is removed, maintaining a conductive flow path.
Question 6: Which type of trap is formed by a fold where reservoir rock is arched into a dome-shaped structure?
- Fault trap
- Anticline trap (Correct answer)
- Stratigraphic trap
- Salt dome trap
Correct answer: Anticline trap
An anticline is an upward-arching fold where buoyant hydrocarbons migrate and accumulate beneath an impermeable cap rock.
Question 7: What is 'ultimate recovery factor' (RF) in petroleum engineering?
- Percentage of original oil in place produced over a field's life (Correct answer)
- Ratio of discovered reserves to exploration cost
- Annual production divided by current reserves
- Recoverable reserves divided by annual demand
Correct answer: Percentage of original oil in place produced over a field's life
Recovery factor is the fraction of original oil (or gas) in place that is ultimately recovered, typically expressed as a percentage.
CMM Exploration & Production Processes 3
What is the purpose of perforating a cased wellbore during completion operations?