Oil and Gas - Production Flashcards
What is a frontier region?
A region that has not been explored much. Geologists must rely on geophysical data to create a model of the subsurface.
What is a wildcat well?
The first well drilled based on a prospect.
What is a dry well?
A well that does not contain enough oil and gas to cover the cost of completing the well.
What is a successful well?
A well that contains enough oil and gas to cover the cost of completing the well.
What is a prospect?
An exploration target that could potentially contain sufficient oil and gas. This is an educated guess made by geologists based on their geophysical model of the subsurface.
What is a development well?
Additional wells to tap into the full potential of the reservoir.
What is a play?
When additional oil and gas reservoirs are discovered in the region, and share a common set of geological characteristics, then the region is called a ‘play’.
What are the 3 types of recovery that occurs in the lifecycle of an oil well?
Primary recovery
- Oil recovered initially by taking advantage of the high pressure in the oil reservoir
- No more than 5% to 15% of the oil in the reservoir can be recovered this way
Secondary recovery
- Methods that partially repressurise the reservoir by injecting water into the reservoir to drive the oil upwards into the well (oil floats on water).
Tertiary recovery (Enhanced oil recovery)
- Methods that scrub the remaining oil from the grains of the reservoir rock, by using steam or CO2
- Water and gas injection (WAG)
A further 30- 45% of the oil can be recovered through secondary and tertiary recovery.
What is WAG?
CO2 acts like a soap, chemically dislodging the oil from the sediment grains of the rock into water.
Water is then injected to recover the oil.
What limits the amount of oil that can be produced from a reservoir?
The cohesiveness between oil and the sediment grains of the reservoir rock.
This kind of grain cohesion also limits the amount of natural gas that can be recovered from the reservoir rock.
What is EOR?
Enhanced oil recovery. Inject CO2 and water alternatively to ‘scrub’ the oil off the sediment grains of the rock into water.
Why are high pressures in the reservoir rock desirable?
They provide the initial lift used to produce the oil and gas (primary recovery). However, the oil recovered this way will taper off as the pressure dissipates.
Describe the production curve for an oil well
A decreasing, downward curve.
What is a production profile for an oil field?
The combined production of oil from multiple oil wells.
Starts with an initial build-up, then a plateau, followed by a gradual decline, and eventually abandonment of the well when there is simply not enough oil to continue operating the well.
The production history of a region, oilfield, or even a well will not always follow a simple rise and then fall in production. Why?
Production can be rejuvenated with the discovery of new reservoirs, or new technologies (WAG) that allow more oil to be recovered from the reservoir.
