OIL lecture 21

As Black Shale is buried

it is heated

Organic matter is first changed by the

increase in temperature into kerogen

which is a solid form of hydrocarbon

Around 90°C

it is changed into a liquid

state, which we call oil

Around 150°C

changed into a gas

Source Rock

A rock that has produced oil and gas

Primary migration

movement out of the source rock to a more porous rock

Secondary migration:

movement through the carrier rock to a trap.

Trap

a structural or stratigraphic feature that allows hydrocarbons

to accumulate in the subsurface.

Reservoir

a rock with sufficient porosity and permeability to allow for hydrocarbon accumulation

Reservoir rock

Open, connected pores

transmit fluid easily.

• Pores coated with

mineral cement will have

a reduced ability to

transmit fluid.

Hydrocarbon trap

In some geological instances impermeable rocks may serve to trap

the buoyant hydrocarbons in a reservoir, allowing them to

accumulate = traps

enhance recovery

a hole

is drilled adjacent to the well

and one of the following: gas,

steam or chemical is pumped down.

These help to solubilize the oil and

push it out of the rock and up into

the well.

only 40-50%

of oil and gas rise up a well to the surface even though naturally they are less dense than water