M
Migration
The movement of hydrocarbons from source to reservoir. Primary migration refers to expulsion from the source itself, secondary migration describes its passage through the reservoir to the trap.
mmbbl
Million barrels
mmboe
Millions of barrels of oil equivalent
mmscfd
Millions of standard cubic feet per day
N
Nitrogen lift
Nitrogen injection into the fluid column to stimulate flow into the well bore.
O
Outcrop
An area of rocks occurring at surface
P
Perforation
Holes in casing and cement (if present) to allow formation fluid to enter the well bore. One common method of perforating is by shooting holes through the casing by means of a 'gun' lowered into the hole. Others use shaped charges to penetrate the casing and up to 36" into the surrounding formation.
Permeability
A measure of the ability of a rock to transmit fluids. It is measured in darcies or milledarcies.
Porosity
Expressed in bulk percentage, it is a measure of the ratio of void space to total rock volume. Fluids occupying porosity in a reservoir may include hydrocarbons.
PSC
Production Sharing Contract
R
Reserves
That portion of the identified resource (oil or gas), from which a usable mineral and energy commodity can be economically and legally extracted at time of determination.
Reservoir
Used to describe subsurface rocks with sufficient porosity and permeability to allow the storage and transmission of fluids (primarily hydrocarbons).
S
Seismic survey
Controlled transmission and recording of energy (vibration) into the ground to delineate subsurface structures and potentially identify hydrocarbon traps
Spud
This term refers to the point in time at which the drill bit begins to turn into the earth and drilling actually starts.
sq km
Square kilometres
Strike
A horizontal straight line on a planar surface perpendicular to the true dip direction. Usually expressed as a azimuth.
T
tcf
Trillion cubic feet
Total Depth
This is the point at which the drilling operation has reached the total intended depth. Once this depth is reached, the operator must analyze the results of the drilling and determine whether the well is to be completed.
Trap
A subsurface feature which can contain hydrocarbon accumulations. Structural traps are a result of deformation of the earth such as folding and faulting. Stratigraphic traps are a result of lateral and vertical variations in rock properties such as permeability and porosity, and may be caused by facies changes.
U
Unconformity
A break in the stratigraphic record. They can be the result of a hiatus in sediment deposition, or a period of uplift and erosion. These may be recognised in the subsurface using stratigraphic correlation between wells or seismic interpretation (angular or landscape unconformities).
$
US Dollar
V
Vug
A large pore or cavity, frequently found in carbonate rocks, which is often lined with minerals
W
Wells
Types of Wells:
Wildcat - a well drilled far from known production in a setting which has no conventional prospectivity.
Exploratory - A well drilled outside the boundaries of a known reservoir.
Development - A well drilled within the boundaries of a known producing reservoir to increase the production in the field.
Offset Well - This is a type of development well that is drilled near a well that is producing or had previously been productive.
