Crude oil extraction ( lec 3a )

dr sb. lecture in uet lahore

1. Locating Oil fields B efore starting the extraction of crude oils, the crude oil fields has been identified. There are number of methods available for this Magnetometer Gravimeter Satellite imagery Seismic surveys Sniffers

2. Magnetometer An instrument used to measure the strength, direction of magnetic fields Measure the change in earth’s magnetic field caused by oil flow

3. 2. Gravimeter An instrument used for measuring earth’s gravitational field Typically designed to measure very tiny fractional changes in earth’s gravitational field Tiny changes in gravitational field can give idea about oil flowing in earth

4. 3. Satellite Imagery Imagery is vital to exploration, geophysical surveying and in determining suitable drill sites based on surface conditions. A high-resolution image acquired prior to exploration and drilling activity serves as a baseline for other activities including site modeling, facilities monitoring, environmental assessments, and vegetation reclamation

5. 4 . Seismic surveys creating shock waves that pass through hidden rock layers and interpreting the waves that are reflected back to the surface In seismic surveys, a shock wave is created by the following : Compressed-air gun  - shoots pulses of air into the water (for exploration over water) Thumper truck  - slams heavy plates into the ground (for exploration over land) Explosives  - detonated after being drilled into the ground (for exploration over land) or thrown overboard (for exploration over water)

6. 4 . Seismic surveys

7. 5 . Sniffers They can detect the smell of hydrocarbons using sensitive electronic noses called sniffers. High-tech devices that act like a "nose" are also used to detect traces of  hydrocarbon  gases that escape from below-surface oil deposits.

8. The oil well is created by drilling a hole into the earth A steel pipe (casing) is placed in the hole, to provide structural integrity to the newly drilled wellbore. Holes are then made in the base of the well to enable oil to pass into the bore Finally a collection of valves is fitted to the top, the valves regulating pressures and controlling flows.

9. Primary Recovery During the primary recovery stage, reservoir drive comes from the natural mechanisms. Natural water displaces oil downward into the well. Recovery factor during the primary recovery stage is typically 5-15%

10. Primary Recovery

11. Secondary Recovery They rely on the supply of external energy into the reservoir in the form of injecting fluids to increase reservoir pressure, hence replacing or increasing the natural reservoir dry Other secondary recovery techniques increase the reservoir's pressure by water injection, natural gas reinjection and  gas lift, which injects  air,  carbon dioxide or some other gas into the bottom of an active well, reducing the overall density of fluid in the wellbore with an artificial drive.

12. Secondary Recovery the recovery factor after primary and secondary oil recovery operations is between 35 and 45 %.

13. Tertiary Recovery This type of method is used where oil is thicker and heavier than normal crude oil. Steam is injected into the oil reservoir to increase its mobility and thus reducing viscosity This method is also called Thermally Enhanced Oil Recovery method (TEOR).

14. Some of the oil is burned to heat the surrounding oil In some cases, surfactants are added to alter the surface tension between oil and water Another method to reduce viscosity is carbon dioxide flooding Recovery rate is 5-15%

15. The amount of oil that is recoverable is determined by 3 major factors: Permeability of the Rocks The Strength of Natural Drives Viscosity of the Oil