Month: July 2009

Probable reserves are those unproved reserves of hydrocarbons which analysis of geological and engineering data suggests are more likely than not to be recoverable. When probabilistic methods are used, there should be at least a 50% probability that the quantities actually recovered will equal or exceed the sum of estimated proved plus probable reserves. Probable reserves may include: (1) reserves to be proved by normal drilling where sub-surface control is inadequate to classify these reserves as proved; (2) reserves in formations that appear to be productive based on well log characteristics, but lack definitive tests and are not analogous to producing and or proved reservoirs in the area; (3) incremental reserves attributable to infill drilling that could have been classified as proved if closer statutory spacing had been proved at the time of the estimate. (4) reserves attributable to improved recovery methods when a project is planned but not yet in operation and/or when rock/fluid and reservoir characteristics appear favorable for commercial application; (5) reserves in an area of the formation that appears to be separated from the proved area by faulting and the geological interpretation indicates the subject area is structurally higher than the proved area; (6) reserves attributable to a future workover, treatment, re-treatment, change of equipment or other mechanical procedures, where such procedure has not been proved successful in wells which exhibit similar behavior in analogous reservoirs and (7) incremental reserves in proved reservoirs where an alternative interpretation of performance or volumetric data indicates more reserves than can be classified as proven.

System adapted in the UK, Norway, Canada, Australia. See probabilistic estimate

The method of estimation of hydrocarbon reserves is called probabilistic when the known geological, engineering and economic data are used to generate a range of estimates and their associated probabilities