Reservoir Fluids and Reservoir Pressure

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Reservoir Fluids and Reservoir Pressure

• Chapter 1 (Part 2)

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Reservoir Fluids

• What is a Fluid?
• Any substance that will flow
• Reservoir Rock Usually Contains three Fluids
• Oil
• Gas (Does not have to be a liquid)
• Salt Water

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Reservoir Fluids (Salt Water)

• Most reservoirs are sedimentary formations that
  were deposited in or near the sea.
• As petroleum formed it displaced the salt water
  around it, but some does remain.
• This is remaining water is called Connate Water
• Connate Water is distributed throughout the
  reservoir.
• Typical Locations are at the Bottom and on the
  Edge of the oil zone.

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Reservoir Fluids (Connate Water)
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Reservoir Fluids (Oil)

• Key Points
• Oil is Lighter than water
• Does not readily mix with water
• Oil will not completely displace water in a
  reservoir
• Film of water sticks to or is absorbed by the
  rock surrounding the oil
• Film is called Wetting Water

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Reservoir Fluids (Oil)
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Reservoir Fluids (Natural Gas)

• Typically contained in reservoirs with oil
• One of the most valuable drives for forcing oil
  out of reservoirs
• Occurs in two principal ways
• Solution Gas
• Free Gas

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Reservoir Fluids (Solution Gas)

• Found in High Pressure Low Temperature Conditions
• Stays in solution in the oil while in the
  reservoir
• When the oil comes to the surface and the
  pressure is relieved, the gas comes out of the
  solution.
• Gas occupies space in the reservoir and is
  calculated when geologists determine the
  reservoir size.

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Reservoir Fluids (Free Gas)

• Gas that is not dissolved in oil
• Tends to accumulate at the highest part of the
  reservoir (Gas Cap)
• Oil in the reservoir will be saturated with gas
  in solution as long as there is a gas cap.
• Dissolved gas lowers the viscosity of the oil
  making it easier to move the oil into the well
  bore.

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Reservoir Fluids (Natural Gas)
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Reservoir Pressure

• Two Types of Pressure
• Normal
• When a reservoir has an outlet to the surface and
  the pressure is caused by the fluids in it.
• Abnormal
• When a reservoir has no outlet and is surrounded
  by impermeable formations. The overlying rock
  formations add to the pressure.

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Reservoir Pressure

• http//www.youtube.com/watch?vRpNM3WZfCo0

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Reservoir Pressure(Injection vs. Production)
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Questions

1. List the three types of fluid found in a
   reservoir formation?
2. What is connate water?
3. Define Wetting Water.
4. Explain the difference between an Oil Wet
   formation and a Water Wet formation.
5. List the two principal ways gas occurs in an oil
   reservoir.
6. Why is the presence of gas important in an oil
   formation?
7. Where does gas tend to accumulate in an oil
   reservoir and what is it called?
8. What happens to the viscosity of oil when gas is
   dissolved into the formation it is found in?
9. List the two types of Reservoir Pressure.
10. List the two different well types found in oil
    production fields.