Hydrocarbon Habitat

Question 1

Name the 5 elements of the Petroleum System

Answer 1

• Source (maturation and migration)
• Reservoir
• Seal
• Trap
• Timing

Question 2

Distinguish between primary, secondary and tertiary migration

Answer 2

Primary: Migration out of source rock and into traps/carrier beds

Secondary: Migration up faults

Tertiary: Reservoir to surface

Question 3

How is oil/gas released from source rocks?

Answer 3

Released from organic matter in mudstones/carbonates when rock is buried (heated and pressurised)

Question 4

What is the most important thing for a source rock to have?

Answer 4

High T.O.C. ( > 1% )

Question 5

How does kerogen type and heating/pressure effect the type of hydrocarbon that is produced?

Answer 5

Rich in land plant material (wood): gas prone

Rich in marine algae: oil prone

Increased temps and pressures > more gas

Question 6

How is kerogen maturity measured?

Answer 6

GCMS or Ro reflectivity

Question 7

How are hydrocarbons expelled from a source rock?

Answer 7

Driven out by overpressure due to volume expansion and buoyancy

Question 8

What controls petroleum migration into carrier beds?

Answer 8

Buoyancy vs capillary forces

Question 9

How does burial effect kerogen composition between: Surface and 0.8 km 0.8 - 1.5 km 1.5 - 3 km > 3 km ?

Answer 9

Surface to 0.8 km: biogenic gas from bacterial degradation of organic matter

0. 8 - 1.5 km: O2 conc decreases and C conc increases, no thermogenic products
1. 5 km - 3 km: generation and release of hydrocarbon between 90-120 degrees Celsius

3 km > gas generation declines until any carbon present ‘dies’

Question 10

Name five ways to geochemically analyse rock samples

Answer 10

• T.O.C.
• Vitrinite: determine burial
• Source rock kinetics: aid modelling/timing of generation
• Age of source rock
• Oil to source correlation

Question 11

Name two sources of fluid that can be sampled

Answer 11

• Wells
• Surface seeps

Question 12

What does analysis of biomarkers allow us to do? (three things)

Answer 12

Identify:

• Depositional environment
• Age of source rock
• Maturity

Question 13

Where are hydrocarbons stored in reservoir rocks?

Answer 13

Either:

Between grains (intragranular)

Within grains (intergranular)

Question 14

What does an effective reservoir need to be? (2 things)

Answer 14

Laterally continuous

Good poroperm characteristics

Question 15

What is characterising reservoir architecture and heterogeneity a function of?

Answer 15

• Depositional environment
• Diagenesis
• Structural configuration and compartmentalisation

Question 16

What does reservoir architecture and heterogeneity influence?

Answer 16

Areal and volumetric sweep efficiency

Question 17

What can enhance recovery factor ?

Answer 17

The more homogenous it is

Question 18

Describe the reservoir characterisation workflow

Answer 18

Question 19

Describe the three reservoir architecture types in terms of recovery factor, well spacing and sweep efficiency

Answer 19

Layered: High recovery factor, good well spacing, high sweep efficiency

Jigsaw: Moderate recovery factor, moderate well spacing, medium sweep efficiency

Labyrinthine: Low recovery factor, well spacing small, low sweep efficiency

Question 20

What tools can we use to characterise a reservoir? What information can they provide?

Answer 20

Seismic:

Structural configuration and faulting,

DHI,

Quantitative reservoir attributes away from borehole (porosity, saturation),

Mapping of reservoir distribution away from borehole

Well data:

Logs (especially image logs)

Geological models:

Depositional, diagenetic and structural