1. AAPG ASUSC . ‫بالبريمة‬ ‫انزل‬ PROSPECT GENERATION . PETROLEUM GEOLOGY SESSION
Conventional vs. unconventional oil
And thermal heavy oil recovery methods
Conventional oil is the product of
the organic matter in deep layers
subjected to temperature and
pressure and migrated from its
source rock towards shallower
beds before it was trapped by an
impermeable bed (seal). It can be
easily (and cheaply) extracted from
the ground using the traditional
methods of drilling (Vertical wells
and the oil will rises without any
additional stimulation).
On the other hand, unconventional
oil is any oil produced by any
method other than traditional
drilling. It is heavy and highly
viscous. It fails to migrate from its
source rock to porous and
permeable reservoirs. Additional
stimulation (hydraulic fracturing) is
needed to be produced. Many
types of source rocks can produce
unconventional oil and gas such as
shale gas, coal beds or low quality
reservoirs (tight gas).
Methods of extraction
. Heating of reservoir by soaking
the reservoir with injected steam.
This is called cyclic steam injection.
Or heating the oil electrically,
possibly powered by a nuclear
reactor .
. Freezing the ground at a distance
from the well.
SAGD Steam assisted gravity drainage
. Two horizontal wells are drilled
. Injected steam forms a ‘’steam chamber’’
. Steam and gases rise filling the void left by oil
. The condensed water and crude oil or bitumen is
recovered to the surface by pumps
CSS Cyclic Steam Stimulation
Stage 1. high pressure steam injected
Stage 2. Major portion of reservoir is thoroughly
saturated
Stage 3. production phase (when production phase
declines another cycle of steam injection begins)