05.07.2009

When exploratory wells find commercially viable natural gas or petroleum deposits, it is economical to build a permanent platform from which well completion, extraction, and production can occur. These large, permanent platforms are extremely expensive, however, and generally require large expected hydrocarbon deposits to be economical to construct. Some of the largest offshore platforms are located in the North Sea, where because of almost constant inclement weather, structures able to withstand high winds and large waves are necessary. A typical permanent platform in the North Sea must be able to withstand wind speeds of over 90 knots, and waves over 60 feet high. Correspondingly, these platforms are among the largest structures built by man. There are a number of different types of permanent offshore platforms, each useful for a particular depth range. Because of their size, most permanent offshore rigs are constructed near land, in pieces. As the components of the rig are completed, they are taken out to the drilling location. Sometimes construction or assembly can even take place as the rig is being transported to its intended destination.

Primary target usually refers to the most important reservoir which an O&G company hopes will contain hydrocarbons when drilling. Secondary target refers to other possible reservoirs that may be above or below the primary target, which are usually thought to be not as attractive for various reasons as the primary target, possibly because they are thinner, of variable quality, are of low poroperm qualities, etc. In real life secondary targets can turn out to be better than primary, or both targets can be good or both bad

The search for an area for probable exploration. The search normally includes geological and geophysical studies of relatively large areas undertaken in an attempt to locate specific areas warranting detailed exploration. Prospecting usually occurs prior to the acquisition of mineral rights.

An area of exploration in which hydrocarbons have been predicted to exist in economic quantity. A prospect is commonly an anomaly that is recommended by explorationists for drilling a well.

A project associated with a potential accumulation that is sufficiently well defined to represent a viable drilling target.

Project activities in this case are focused on assessing the chance of discovery and assuming discovery, the range of potential recoverable quantities under a commercial development program

The allocation of production among reservoirs and wells or pipeline allocation of capacity among shippers, etc.

See pro-rata allocation and see priority allocation separately, for LNG gasification facilities

When gas is allocated on a pro-rata basis in an LNG gasification facility, such as pro-rata to booked quantities, under the open access system