Exploration & Appraisal – Introduction and Background

Oil and gas exploration is the search for hydrocarbon deposits beneath the Earth's surface and consists of several elements from surveying the geological structures to drilling exploration wells to appraising discoveries.

Once the environmental and seismic surveys are completed, and if the results look good, drilling an exploratory well is considered. Even at this stage, it remains an uncertain business with no guarantees. There is still a high risk that nothing at all will be found, or that the oil will be in such small quantities that it would not be worthwhile extracting it.

If an exploratory well shows that hydrocarbons are present, more seismic data is gathered and then a number of appraisal wells are drilled and more data is collected. From this data it is possible to estimate how much oil and gas the field contains, how difficult it will be to extract and what percentage of the oil and gas can be extracted. Unfortunately, it's not possible to get every last drop of oil out of a reservoir - in the North Sea; for example, operators expect to recover about 40 - 50% of the total reservoir.

Oil exploration involves lots of people with different skills, for example geologists, geophysicists, surveyors, mud loggers, computer scientists, marine biologists, drilling engineers, the drilling crew. Alongside these are all the people employed back onshore for example economists, planners, lawyers, IT specialists, environmental advisers and safety advisors to name a few.

Exploration and Appraisal – Key Statistics and Commentary

Despite a slow start to the year, exploration and appraisal (E&A) activity remained buoyant during 2006, supported by high oil prices. The total number of wells drilled declined slightly to 69, but intentions to drill outweighed resource capacity. The tightness of the rig market and a reasonably successful exploration year in 2005 saw efforts being concentrated on appraisal wells in 2006, with 40 being drilled versus 29 exploration ones. Many planned exploration wells were delayed until 2007, but the first quarter of this year has not seen a rebound, with nine exploration and seven appraisal wells being drilled.

UKCS Drilling: E&A Wells by Region 1999-2008

Exploration and Appraisal – Supplementary Statistics and Commentary

For more information, see the Supplementary Statistics Section.