Unformatted text preview: by severe faulting. The hydrocarbons would be less separated with more gas in solution and oil of reduced viscosity because of higher temperatures. There is often a reduction in porosity and permeability due to increased compaction. 2. Area and Thickness The total area of a reservoir and its thickness are of considerable importance in determining if a reservoir is a commercial one or not. The greater the area and thickness of the reservoir, the greater the potential for large accumulations of oil and gas. However, there are reservoirs that produce substantial amounts of hydrocarbons that are not of considerable size. 3. Porosity It is the percentage of pore volume or void space to the total volume of rock. • Primary porosity: The porosity preserved from deposition through lithification. • Secondary porosity: created through alteration of rock, commonly by processes such as dolomitization, dissolution and fracturing. • Total porosity: is the total void space and as such includes isolated pores and the connected pores • Effective porosity: The interconnected pore volume or void space in a rock that contributes to fluid flow or permeability in a reservoir. Primary porosity Secondary porosity 4. Permeability It is the ability of the rock to transmit fluids, to be permeable; a formation must have interconnected porosity (Unit is Darcie) • Absolute permeability: ability to flow or transmit fluids through a rock, conducted when a single fluid, or phase, is present in the rock. • Effective permeability: The ability to preferentially flow or transmit a particular fluid when other immiscible fluids are present in the reservoir. If a single fluid is present in a rock, its relative permeability is 1.0 • Relative permeability: is the ratio of effective permeability of a particular fluid at a particular saturation to absolute permeability of that fluid at total saturation. 30 Geology & Geophysics in Oil Exploration Mahmoud Sroor Geology & Geophysics in Oil Exploration 4‐Seal (Ca...
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- Spring '10
- Geology, Volcano, Tephra, Volcanic Ash, Geology & Geophysics, Mahmoud Ahmed Sroor