Oil & Gas Glossary 1.0

The percentage that the volume of the pore space bears to the total bulk volume. The pore space determines the amount of space available for storage of fluids.

The ability of a rock to transmit fluid through the pore spaces. - A key influence on the rate of flow, movement and drainage of the fluids. There is no necessary relation between porosity and permeability. A rock may be highly porous and yet impermeable if there is no communication between pores. A highly porous sand is usually highly permeable. A measure of the ease with which a fluid flows through the connecting pore spaces of rock or cement. The unit of measurement is the millidarcy. Fluid conductivity of a porous medium. Ability of a fluid to flow within the interconnected pore network of a porous medium.

2. replacement of one fluid by another in the pore space of a reservoir. For example, oil may be displaced by water.

An opening or space within a rock or mass of rocks, usually small and often filled with some fluid (water, oil, gas, or all three). Compare vug.

The amount of the pore volume of a reservoir rock that is filled by water, oil, or gas and measured in routine core analysis.

2. a small cavern, larger than a pore but too small to contain a person. Typically found in limestone subject to groundwater leaching.

The percentage of the total bulk volume of a rock sample that is composed of pore spaces or voids. See porosity.

Water inherent to the producing formation; or fossil sea water trapped in the pore spaces of sediments during their deposition.

The flux of fluids and solids that occurs in the initial stages of any filtration before pore openings are bridged and a filter cake is formed. Also called spurt loss.

The percentage of the bulk volume of a rock sample that is composed of interconnected pore spaces that allow the passage of fluids through the sample. See porosity.

Water retained in the pore spaces, or interstices, of a formation from the time the formation was created.

A measure of the ability of a single fluid to flow through a rock when another fluid is also present in the pore spaces. Compare absolute permeability, relative permeability.

A device that controls the rate of flow of fluid in a line or opens or shuts off the flow of fluid completely. When open, the sealing surface of the valve is moved away from a seat; when closed, the sealing surface contacts the seat to shut off flow. The direction of movement of the valve is usually perpendicular to the seat. Popper valves are used extensively as pneumatic (air) controls on drilling rigs and as intake and exhausts valves in most internal-combustion engines.