Nostra Terra is an oil and gas exploration and production company listed on the AIM, a market operated by the London Stock Exchange (LSE: NTOG)

Focused on achieving profitable, rapid and sustainable growth, which generate returns for our shareholders, we have a diverse and growing portfolio of producing and exploration assets with capital in place to continue development.

In this section, you will find links to information for all existing and potential shareholders.




O&G Glossary

API gravity

The American Petroleum Institute gravity is a measure of how heavy or light a petroleum liquid is compared to water. It is measured in degrees and the higher the API, the lighter the crude.


To cease work on a well which is non-productive/uneconomic


A process whereby acid is pumped at high pressure into a reservoir in an attempt to dissolve some of the rock and improve wellbore flow characteristics. Often used in conjunction with fracturing


The area over which a company has hydrocarbon exploration interests

American Petroleum Institute (API)

The oil and gas industry’s trade organization. API’s research and engineering work provides a basis for establishing operating and safety standard issues and specifications for the manufacturing of oil field equipment and furnishes statistical and other information to related agencies. Visit API at


The space between the drill string and the well wall, or between casing strings, or between the casing and the production tubing.


potential traps formed when strata forms into the shape of a dome-like fold.

Appraisal well

Well drilled after the field has been discovered to appraise its content.

Associated gas

Natural gas associated with accumulation of oil. May be dissolved in the oil or may form a cap of free gas above the oil.


Barrels of oil equivalent per day

Back off

To unscrew one piece of drill pipe from another. Also used to describe the process of using wireline conveyed small explosives to help unscrew a specific joint of pipe deep underground when a pipe is stuck and all other attempts to free it have failed.


Used during drilling to improve the condition of the hole. The drill pipe is run up and down over problem zones repeatedly whilst rotating the bit and circulating mud.

Barrel (BBL)

One stock tank barrel. The most commonly used unit of measurement for petroleum and its products (7.33 barrels = 1 ton or 6.29 barrels = 1 cubic meter). Represents 42 gallons of liquid volume.

Barrel of oil equivalent (BOE)

A measure used to aggregate oil and gas resources or production, with one BOE being approximately equal to 6,000 cubic feet of natural gas.


A large, natural depression on the Earth’s surface in which sediments, generally brought by water, accumulate.


The geological term defining a stratum of any thickness and of uniform homogenous texture.


A sophisticated cutting tool used in drilling. There are two main types of bit used in drilling oil/gas wells: rock bits and diamond bits.


An acreage sub-division. Although varies from country to country, generally tends to be approximately 10 x 20 kms.

Blow out

Occurs during drilling when reservoir pressure exceeds the ability of the well-head valves (BOP) to control it, resulting in uncontrolled ejection of wellbore fluid from the top of the well.

Blow-out Preventor (BOP)

High pressure wellhead valve which is designed to seal the well quickly in the event of an uncontrolled flow of hydrocarbons.


The hole as drilled by the drill bit.

Bottom Hole Assembly (BHA)

Lower part of drill string from the bit to the drill pipe. Can consist of drill collars, stabilisers mud motors and a bit amongst others. Provides weight for the bit to cut rock.

Bottoms up

Circulation of drilling fluid in a well, so that mud from the bottom of the drill pipe is pumped back to surface.

Cap rock

Impermeable rock overlaying a reservoir.

Cased hole

Hole in which casing has been set.


The steel lining that supports the sides of the well and prevents the flow of fluid both from and into the well bore.

Casing shoe

A reinforced section of casing placed on the bottom of the casing string that protects against damage.


The pit dug in the ground beneath the drill floor for land drilling, often lined with cement for larger wells.


The filling of the space between the casing and the borehole wall with cement. This ensures the casing remain stationary and also prevents any leakage.

Christmas Tree

An assembly of valves, spools and fittings for an oil well, named for its resemblance to a decorated tree. Its function is to prevent the release of oil/gas from an oil well and to direct and control the flow of formation fluids from the well.


The removal of wellbore-fill material such as sand, scale or organic materials, and other debris from the wellbore. Many reservoirs produce some sand or fines that may not be carried to the surface in the produced fluid. Accumulations of fill material may eventually increase in concentration within the lower wellbore, possibly restricting production. Cleanouts using coiled tubing, snubbing or hydraulic workover techniques are performed routinely.


An oil refinery processing unit that converts the residual oil into lighter hydrocarbon gases, naphtha, light and heavy gas oils and petroleum coke.

Cold filter plugging point (CFPP)

The temperature at which a standard fuel filter will clog.


The process of making a well ready to produce natural gas or oil. Completion involves installing permanent equipment, such as a wellhead, and often includes hydraulic fracturing.


Hydrocarbons which are gaseous under reservoir conditions, but which become liquid when temperature or pressure is reduced.

Contingent Resources

Those quantities of hydrocarbons which are estimated to be potentially recoverable from known accumulation, but which are not yet commercially recoverable.

Conventional resources

Discrete accumulations of hydrocarbons contained in rocks with relatively high matrix permeability, which normally have relatively high recovery factors.


Process which alters the size and/or structure of hydrocarbons in other to further upgrade the crude output in order to give a higher yield of more valuable products such as gasoline. See Cracking, unification and alteration.


Break down heavier hydrocarbon molecules into lighter products using heat (thermal) or by the addition of catalysts (catalytic).

Creaming curve

A plot of the number of discoveries against the number of wells in a basin in order to estimate the quantity of ultimate basin reserves.