A brief view about the Extraction of Petroleum products from subsurface by using different methods. Muhammad Wajid Manzoor Institute of Geology Punjab University Lahore, Pakistan

1. PRODUCTION METHODS

2. • There are three natural drive mechanisms can cause oil or gas flow
up to well bore.
1. Water drive
2. Gas drive
3. Gas solution (Dissolved gas)

3. WATER DRIVE
• In water drive production, oil or gas trapped in a reservoir can be view as
being sealed in a water filled U.tube.
• When tap is opened the oil or gas from the reservoir will flow upward due
to the hydrostatic head of water.

4. • As the field is produced, water invades the lower part of trap to displace
the oil.
• Only in case of uniform reservoir the oil, water contact rise evenly ,
Because the adjacent beds have same permeability , water enrichment at
different rates giving rise to fingering.
• A further complication may be caused by coning of water adjacent to the
boreholes.
• The extent of coning depends on the rate of production and ratio
between vertical and horizontal permeability .

6. • With an effective water drive the flow rate remains constant during the life of fluid
flow but oil production declines inversely with an increase in water production.
• The water drive mechanism is generally most effective , with a recovery factor of
60%.

7. GAS CAP DRIVE
• In gas cap drive mechanism field contains both oil and gas zones.
• as production begins the drop in pressure cause gas dissolved in oil to
come out of the solution.
• This gas move up to the gas cap and expands to occupy the pores vacated
by oil. A transitional zone of degassing thus forms at gas, oil contact.
• Drawdown zones may b developed adjacent to bore holes in a manners
analogues to but reverse to the coning of oil, water contact.
• The production history of gas cap drive fields is different from the water
drive mechanism.

9. • Pressure and oil production drop steadily , while the ratio of gas to oil
increase naturally.
• Less effective than water drive mechanism ,with a recovery factor of 20-50%.

10. DISSOLVED GAS DRIVE
• This type of drive occurs in the fields that initially don’t have any gas cap,
also known as solution gas drive mechanism.
• As production begins , pressure drops , gas bubbles form in the oil ,
expands forcing the oil out of pore system and towards the borehole.
• Initially gas bubbles separated as time passes, they come together and
form a continuous free gas phase, which may accumulates as gas cap.
• This point is termed as critical gas saturation, and care should be taken to
prevent from this point.

11. • It may be avoided by slow rate of production or by reinjecting the
produced gas to maintain the original reservoir pressure.
• This drive mechanism is less effective than the other two types , with a
recovery factor of 7-15% .

12. ENHANCED OIL RECOVERY
• One of the main objective of enhanced recovery oil is to maintain or
reestablished the original reservoir pressure.
• This objective can be accomplished by several ways :
 By injecting gas ( Inert gases e.g. Carbon dioxide , Nitrogen).
 By injecting liquids ( Sea water , connate water ).