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14 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Secondary Recovery |
After the underground pressure decreases to a point where primary recovery no longer works, Secondary recovery relies on supplying external energy by injecting fluids to the reservoir to increase reservoir pressure. |
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Typical Recovery Factor of secondary recovery |
Approx. 30% of OOIP |
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Typical recovery factor after both primary and secondary recovery |
35%-45% of OOIP |
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What are 2 common secondary methods |
-Water flood aka Water Injection -Gas Flood aka Gas Lift |
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What 2 categories are Gas Flood divided into |
-Immiscible Gas Flood -Miscible Gas Flood |
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What is Waterflood |
Water is injected into the reservoir to: -Fill pore spaces left by oil that’s been removed -Maintain the reservoir pressure -Displace the oil from the pores |
As a recovery method |
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What is the most commonly used Secondary Recovery Method and Why? |
Water-flood because of the availability and low cost of water and it’s effectiveness in most cases |
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What does the effectiveness of Waterflood depend on? |
-Properties of the oil (low viscosity enables oil to flow readily) -Geological structure and rock properties, which affect the flow path of water |
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How long can Waterflood take and what are it’s limitations? |
May take several decades to complete Limitations include: -Compatibility of the injected water and the reservoir water -Injected water may dissolve rocks or form viscous clay slurry -Oxygen, bacteria and chemicals need to be removed from injected water -Process complexities in treating produced water with oil, scale-forming minerals or Naturally-occurring radioactive material (NORM) |
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What is Polymer Flood |
Sometimes follows Waterflood -Water is injected first -Polymer follows water -Polymer reduces the surface tension of the oil; so oil flows easier
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Is Polymer Flood a cost effective process? |
No it is an expensive method |
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What is Gas Flood (Gas lift) |
-Injecting a high pressure stream of gas from surface into well -Hydrostatic head (weight of fluid column) above the oil reservoir is reduced. -More oil can flow into the wellbore and be moved by the reservoir pressure to the surface |
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Immiscible Gas Injection Process |
-A lean (light) gas is injected to maintain the reservoir pressure (gas cap) that forces oil into the wellbore -The gas is typically the produced gas that is compressed at the surface and re-injected. It may come from an external source -If gas is dissolved into the oil, the “swelling” reduces the oil viscosity and density which enhances flow -the gas may strip out some hydrocarbon (propane, butane) from the reservoir oil which can then be recovered as liquids -the gas may not be very effective is displacing oil from the rock pores due to its high mobility |
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Miscible Gas Injection |
-CO2 is injected to reduce oil density and viscosity by dissolving in the oil -due to greenhouse gas concerns, there is benefit to capture CO2 from flue gas (gas exiting to the atmosphere from power plants etc) -captured CO2 May then be used for EOR in the oil field -carbon capture |
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