Production of HC
without add extra
energy to reservoir
NATURAL DRIVES
COMPACTION DRIVE
rock & liquid expansion
materials present: crude oil, connate water, rock
as reser. press decr. -> rock& fluid expand due to
their compressibilities-> grains expand-> bulk
volume incr. -> reduce poro/pore V + fluid expand
-> oil & water force out of pore space to wellbore
liquids & rock: slightly compressible -> can
overcome the press drop due to production->
rapid press decline during production
constant GOR = gas solubility at bubble point press
least effective
drive: only
recover small
% OIIP
DEPLETION DRIVE
As production, Press decr. < bubble Press ->
gas form (GAS LIBERATION from oil)+ expand ->
push oil to wellbore -> incr. oil production->
until reach critical press-> gas get inside
wellbore instead of oil-> reduce oil production
also called SOLUTION GAS
/DISSOLVED GAS/
INTERNAL GAS
press decr. rapidly & continuously. little/no water
production. rapid inc. GOR . rapid incr. oil production
until reach critical press at which rapid decr.
5-30% recovery OIIP, best
for secondary recovery
GAS CAP DRIVE
As press decr. during production -> gas cap expand (gas
expand to occupied V loss by oil produced + gas liberate
from oil) to maintain press -> push the oil to well bore
Develop wells positions: drills many wells at
different depth -> determine GOR production from
these wells -> shut down wells which produced
excessive gas or use to re-inject gas back to reservoir
present of a gas cap
with little/no water
drive
Press fall slow, continuously. no/little water produce. GOR rise continuously
20-40%,larger
recovery than
depletion drive
incr. size of gas cap, high vertical
permeability, low oil viscosity ->
greater Gas cap drive -> inc.
recovery % OIIP
WATER DRIVE
as production, Press decr. & V of oil decr. ->
water replace oil V (water move into pore
space)-> maintain press -> push oil to wellbore
as compactivity of water < oil, water source in
reser. need to connect to a large water body
At water invaded zone, polymers can
be inject to inc. viscosity so the water
can get through oil to wellbore
Gradual press decline (water maintain
press drop). little change in GOR.
much higher
recovery % OIIP
than other
drives. 35-75%
GRAVITY-DRAINAGE DRIVE
need a slow flowrate of production for
gas to have time to move up to the gas cap
As production, press decr. -> gas lubricate
from oil -> go up to gas cap due to gravity
(gas density < oil density) -> opposite
force push oil down & into wellbore
bigger gas cap -> greater gravity-drainage drive
occur as result of difference
densities of reser. fluids
rapid press decr. Low GOR. form
secondary gas cap in undersaturated
reser. little/no water produce.
can excess 80% recovery OIIP
COMBINATION DRIVE
combination of different natural
drives in one reservoir