Podcast
Questions and Answers
Porosity is defined as the ratio of void space, or ______ volume, to the total bulk volume of the rock.
Porosity is defined as the ratio of void space, or ______ volume, to the total bulk volume of the rock.
pore
Hydrocarbon porosity is part of the porosity that contains ______.
Hydrocarbon porosity is part of the porosity that contains ______.
hydrocarbon
Absolute porosity is the ratio of the total ______ space in the rock to that of the bulk volume.
Absolute porosity is the ratio of the total ______ space in the rock to that of the bulk volume.
pore
Effective porosity is the percentage of ______ pore space with respect to the bulk volume.
Effective porosity is the percentage of ______ pore space with respect to the bulk volume.
Saturation is the fraction, or percent, of the ______ volume occupied by a particular fluid.
Saturation is the fraction, or percent, of the ______ volume occupied by a particular fluid.
______ porosity ranges from 10% to 40% for sandstone type reservoirs.
______ porosity ranges from 10% to 40% for sandstone type reservoirs.
Two distinct types of porosity are ______ porosity and effective porosity.
Two distinct types of porosity are ______ porosity and effective porosity.
The ______ of a fluid to spread on or adhere to a solid surface in the presence of other immiscible fluids is called wettability.
The ______ of a fluid to spread on or adhere to a solid surface in the presence of other immiscible fluids is called wettability.
Changing the type of ______ or fluid can change IFT and hence the wettability of the system.
Changing the type of ______ or fluid can change IFT and hence the wettability of the system.
Adding a chemical such as ______ can alter wettability.
Adding a chemical such as ______ can alter wettability.
The wettability of a rock-fluid system depends on ______.
The wettability of a rock-fluid system depends on ______.
The total volume of the fluid is the sum of the volume of ______, oil, and water.
The total volume of the fluid is the sum of the volume of ______, oil, and water.
The equation Sg + So + Sw = 1.0 represents the total ______ of the fluid.
The equation Sg + So + Sw = 1.0 represents the total ______ of the fluid.
Wettability is measured by ______ angle, which is always measured through the denser phase and is related to interfacial energies.
Wettability is measured by ______ angle, which is always measured through the denser phase and is related to interfacial energies.
The pressure difference across the curved interface formed by two immiscible fluids in a small ______ tube is known as capillary pressure.
The pressure difference across the curved interface formed by two immiscible fluids in a small ______ tube is known as capillary pressure.
Capillary pressure is equal to the pressure of ______ wetting phase minus the pressure of non-wetting phase.
Capillary pressure is equal to the pressure of ______ wetting phase minus the pressure of non-wetting phase.
There are three types of capillary pressure: water-oil capillary pressure, gas-oil capillary pressure, and gas-______ capillary pressure.
There are three types of capillary pressure: water-oil capillary pressure, gas-oil capillary pressure, and gas-______ capillary pressure.
Permeability is a property of the porous medium that measures the capacity and ability of the formation to transmit ______.
Permeability is a property of the porous medium that measures the capacity and ability of the formation to transmit ______.
The ______ between oil and solid is represented by the symbol σos.
The ______ between oil and solid is represented by the symbol σos.
The ______ is the angle at the oil-water-solid interface measured through the water phase.
The ______ is the angle at the oil-water-solid interface measured through the water phase.
The interfacial energy between oil and water is represented by the symbol ______.
The interfacial energy between oil and water is represented by the symbol ______.
Absolute permeability is the ability of a rock to transmit a single fluid when it is 100% saturated with that ______.
Absolute permeability is the ability of a rock to transmit a single fluid when it is 100% saturated with that ______.
Effective permeability refers to the presence of two ______ in a rock, and is the ability of the rock to transmit a fluid in the presence of another fluid when the two fluids are immiscible.
Effective permeability refers to the presence of two ______ in a rock, and is the ability of the rock to transmit a fluid in the presence of another fluid when the two fluids are immiscible.
Relative permeability is the ratio between effective permeability of a ______ at partial saturation, and the permeability at 100% saturation.
Relative permeability is the ratio between effective permeability of a ______ at partial saturation, and the permeability at 100% saturation.
Rock-matrix compressibility is the fractional change in volume of the solid ______ material with a unit change in pressure.
Rock-matrix compressibility is the fractional change in volume of the solid ______ material with a unit change in pressure.
Rock-bulk compressibility is the fractional change in volume of the ______ volume of the rock with a unit change in pressure.
Rock-bulk compressibility is the fractional change in volume of the ______ volume of the rock with a unit change in pressure.
Pore compressibility is the fractional change in volume of the ______ space with a unit change in pressure.
Pore compressibility is the fractional change in volume of the ______ space with a unit change in pressure.
Rock-matrix compressibility is denoted by the symbol ______.
Rock-matrix compressibility is denoted by the symbol ______.
Rock-bulk compressibility is denoted by the symbol ______.
Rock-bulk compressibility is denoted by the symbol ______.
Study Notes
Review of Rock Properties
- Porosity, ∅, is the ratio of void space or pore volume to the total bulk volume of the rock.
- Hydrocarbon porosity is the part of the porosity that contains hydrocarbon, calculated by multiplying the total porosity by the fraction of the pore volume that contains hydrocarbon.
- Two types of porosity:
- Absolute porosity: the ratio of the total pore space in the rock to the bulk volume.
- Effective porosity: the percentage of interconnected pore space with respect to the bulk volume.
Saturation
- Saturation is the fraction or percentage of the pore volume occupied by a particular fluid (oil, gas, or water).
- Formula for saturation: 𝑓𝑙𝑢𝑖𝑑 𝑠𝑎𝑡𝑢𝑟𝑎𝑡𝑖𝑜𝑛 = 𝑡𝑜𝑡𝑎𝑙 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑙𝑢𝑖𝑑 / 𝑝𝑜𝑟𝑒 𝑣𝑜𝑙𝑢𝑚𝑒
- Saturation values:
- So: oil saturation
- Sg: gas saturation
- Sw: water saturation
- 𝑆𝑔 + 𝑆𝑜 + 𝑆𝑤 = 1.0
Wettability
- Wettability is the tendency of one fluid to spread on or adhere to a solid surface in the presence of other immiscible fluids.
- Measured by contact angle, which is related to interfacial energies by 𝜎𝑜𝑠 − 𝜎𝑤𝑠 = 𝜎𝑜𝑤 cos 𝜃
- Contact angle is measured through the denser phase.
- Changing the type of rock or fluid can change the wettability of the system.
Capillary Pressure
- Capillary pressure is the pressure difference across the curved interface formed by two immiscible fluids in a small capillary tube.
- Formula: 𝑃𝑐 = 𝑃𝑛𝑤 − 𝑃𝑤
- Three types of capillary pressure:
- Water-oil capillary pressure, 𝑃𝑐𝑤𝑜
- Gas-oil capillary pressure, 𝑃𝑐𝑔𝑜
- Gas-water capillary pressure, 𝑃𝑐𝑔𝑤
Permeability, k
- Permeability is a property of the porous medium that measures the capacity and ability of the formation to transmit fluids.
- Absolute permeability: the ability of a rock to transmit a single fluid when it is 100% saturated with that fluid.
- Effective permeability: refers to the presence of two fluids in a rock, and is the ability of the rock to transmit a fluid in the presence of another fluid when the two fluids are immiscible.
- Relative permeability: the ratio between effective permeability of fluid at partial saturation, and the permeability at 100% saturation (absolute permeability).
Rock Compressibility
- There are three different types of compressibility that must be distinguished in rocks:
- Rock-matrix compressibility, 𝑐𝑟
- Rock-bulk compressibility, 𝑐𝐵
- Pore compressibility, 𝑐𝑝
- Rock-matrix compressibility: the fractional change in volume of the solid rock material (grains) with a unit change in pressure.
- Formula: 𝑐𝑟 = −(1/𝑉𝑟) (𝜕𝑉𝑟/𝜕𝑝) 𝑇
- Rock-bulk compressibility: the fractional change in volume of the bulk volume of the rock with a unit change in pressure.
- Formula: 𝑐𝐵 = −(1/𝑉𝐵) (𝜕𝑉𝐵/𝜕𝑝) 𝑇
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Description
Learn about the basics of rock properties in reservoir engineering, including porosity, bulk volume, and hydrocarbon porosity. Review the fundamental concepts and formulas.
