1. Simple Model of HC Migration
Generate oil and gas at lower left
HCs ‘percolate’ into porous interval (white)
Trap A fills with oil and gas – gas displaces oil
Trap B fills with spilled oil and gas
Seal at B will only hold a certain thickness of gas
At trap B – gas leaks while oil spills
Trap C
Slide 32
This animation shows output from a HC migration software package
Buoyancy is the driving mechanism and rock properties have to be defined
In this example, Trap A has a very good seal – it has early oil fill which is displaced by late gas
Trap B has a good seal for oil but allows gas to leak once the gas thickness exceeds a critical value
Trap B maintains an oil leg – the gas can not displace all the oil since it leaks through the top seal
Excess oil in Trap B (with some dissolved gas) spills into Trap C
This is a 2-D model to help show conceptually the types of HC migration that could occur
Rock properties can be varied (e.g., stronger to weaker seals, different source rock properties)
We can build 3-D migration models as well, but often we do not have adequate data to constrain the results
We model different scenarios, but can not say which is correct pre-drill
Trap B
Migration Path
Of Spilled Oil
Spillage of
Excess Gas
“Gas separator”
Trap A
Traps with unlimited charge
Source
Generating HCs
Courtesy of ExxonMobil
L12 – Data Analysis