Geology Flashcards
What is key determinant of the volume of a reserve? What is maximum porosity of a rock
- Porosity
2. 30-35%
What are the areas called where oil accumulates under an impermeable rock (upside down Australian bowl)?
Traps
Key determinant of porosity?
Rock density (identifiable by seismic)
Why do you frack shale rock? What’s the disadvantage vs conventional recovery?
- To increase permability
2. Temporary and thus shorter flow time
How can you increase productivity of low porous calcium rocks?
Acidization via hydrochloric acid
How is oil like water and syrup? Which likeness is preferred and how is the variation referred to?
Oil can vary in viscosity like water through to syrup.
Water like viscosity is preferable as it flows more easily.
The relative viscosity is referred to as the API
How do you improve viscosity?
- Huff and Puff. Inject steam for two weeks, produce until it cools, steam again and repeat
What is the typical well recovery rate of recoverable reserves? What is the maximum?
30-35%
70-75% (ie Draugen fen Norway)
Why would you drill an appraisal well, beyond the depth of the reservoir?
The aquifer under the oil reservoir “powers” the well by pressuring the oil reservoir. You could drill beyond the depth to understand the size of this power source,
What is GOC?
What is WOC?
Gas - Oil Contact, point in the reservoir where oil meets gas
Oil - Water Contact
What is ODT when is it used?
Oil down to
Refers to the depth to which a well has been drilled and referred to in estimating reserves. Not allowed to estimate / record reserves that are hoped to be below the ODT
What makes it difficult to produce from different depths within a single well? What is a key driver of this difficulty?
Pressure differentials at different depths can lead to flows between the producing depths, rather than flowing out to production.
Faults in the rock most commonly facilitate pressure differences between areas rather than having a homogenous well.
What can you do to produce from multiple depths and pressures within a single well?
smart completions enable this type of production. The well will have doors / valves that let you control production from different levels and pressures. As particular areas are depleted and turn to water or other problems faced, you can close in that section and keep producing.
