Reservoir Petrophysics with Hydrocarbon Phase Analysis | Midterm Exam

Porosity

Porosity

a measure of the storage capacity

Absolute porosity

ratio of the total pore space

Effective porosity

percentage of interconnected pore space

Saturation

- fraction or percent of the pore volume

Capillary forces

- forces retaining the water

Critical oil saturation

- the saturation of the oil must exceed a certain value

Residual oil saturation

- remaining oil left

Movable oil saturation

- fraction of pore volume occupied by movable oil

Critical gas saturation

- gas phase remains immobile until its saturation exceeds a certain saturation

Critical water saturation

• maximum water saturation

Wettability

- tendency of one fluid

Surface tension

- forces acting on the interface

Interfacial tension

- when the interface is between two liquids

Capillary pressure

- when two immiscible fluids are in contact

Capillary Hysteresis

- pore spaces of reservoir rocks were originally filled with water

Drainage process -

process of generating the capillary pressure

Imbibition process

- reversing the drainage process by displacing the nonwetting phase

Capillary hysteresis

- process of saturating and desaturating a core

Transition zone

– vertical thickness

Zero capillary pressure

- free water level

Leverett J-Function

- dimensionless function of saturation

Permeability

- property of the porous medium

Darcy’s Law

- equation that defines permeability in terms of measurable quantities

Darcy

– he developed a fluid flow equation

1000 md

1 Darcy =

Dry gas

- usually used in permeability determination because of its convenience, availability, and to minimize fluid-rock reaction

Klinkenberg

- discovered that permeability measurements made with air

Mean pressure

- defined as upstream flowing

Jones (1972)

- studied the gas slip phenomena

Weighted-Average Permeability

- averaging method is used to determine the average permeability of layered-parallel beds

Warren and Price (1961)

- illustrated experimentally that the most probable behavior of a heterogeneous formation

Calhoun (1976)

- suggested that in an ideal pore configuration

Effective permeability

- as the saturation of a particular phase decreases, the permeability to that phase also decreases

Effective overburden pressure

- pressure difference between overburden and internal pore pressure

Rock-matrix compressibility

- defined as the fractional change in volume of the solid rock

Rock-bulk compressibility

- defined as the fractional change in volume of the bulk volume

Pore compressibility coefficient

- defined as the fractional change in pore volume of the rock

Formation compressibility

- total compressibility

Geertsma

- stated that in a reservoir only the vertical component

Formation compressibility

- same order of magnitude

Newman (1973)

- used 79 samples

Reservoir heterogeneity

- variation in reservoir Properties

Degree of homogeneity

- a number that characterizes the departure

Dykstra and Parsons (1950)

- introduced the concept of the permeability variation coefficient

Relative permeability

- the ratio of effective permeability

Stone (1970)

- developed a probability model to estimate three-phase relative permeability

Minimum oil saturation

- a nonzero residual oil saturation

specific gravity

RESERVOIR FLUID PROPERTIES

- the ratio of the gas density

specific volume

RESERVOIR FLUID PROPERTIES

- volume occupied by a unit mass

density

RESERVOIR FLUID PROPERTIES

- ideal gas mixture

gas

RESERVOIR FLUID PROPERTIES

• homogeneous fluid

Gas viscosity

RESERVOIR FLUID PROPERTIES

• measure of the internal fluid friction

Petroleum reservoirs

the result of sedimentary processes

Nonassociated Gas

- reservoirs that contain almost entirely natural gas

Dry gas

- if the fluid at the surface still remains gas

Wet gas

- if the surface pressures cause some liquid hydrocarbons to evolve

Associated Gas

- almost all oil reservoirs except those classified as extra heavy or tars will produce some natural gas at the surface

Unconventional Gas

• geological setting and rock type

Tight gas

- formed in sandstones

Coalbed methane (CBM)

- methane gas that is found adsorbed in many buried coalbed deposits

Shale gas

- found in organic shale rocks

Natural gas phase behavior

- function of pressure, temperature, and volume

Bubble Point Curve

- the curve that separates the pure liquid phase from the two-phase

Dew Point Curve - the curve that separates the pure gas phase from the two-phase

Critical Point

- the point on the phase envelope where the bubble point curve meets the dew point curve

Cricondentherm

- the highest temperature at which liquid and vapor can coexist

Cricondenbar

- the highest pressure at which a liquid and vapor can coexist

Retrograde condensate systems and reservoirs

- unique phenomenon that appears only among hydrocarbon mixtures.

Gas specific gravity

- the ratio of the molecular weight

Viscosity

- a measure of a fluid’s internal resistance to flow.