36 Reserves are classified based on the degree of certainty. There are three types: RESERVE CLASSIFICATION Proved reserves Can be estimated with a high degree of certainty to be recoverable. The amount ultimately recovered will likely exceed the estimated proved reserves. Proved reserves should be established with a 90% probability that the quantities actually recovered will exceed or equal the estimated proved reserves. Probable reserves Less certain to be recovered than proved reserves. The amount ultimately recovered is just as likely to be less than the estimated proved and probable reserves put together as it is to exceed it. Probable reserves should be established with at least a 50% certainty that the quantities actually recovered will equal or exceed the sum of the estimated proved plus probable reserves. Possible reserves Additional reserves less certain to be recovered than probable reserves. The amount ultimately recovered will be unlikely to exceed estimated proved plus probable plus possible reserves put together. Possible reserves should be established with at least a 10% probability that the quantities actually recovered will equal or exceed the sum of the estimated proved plus probable plus possible reserves. Source: National Instrument 51-101 Each classification of reserve can be further broken down into two sub-types: developed and undeveloped. RESERVE CLASSIFICATION BREAKDOWN Developed reserves These are reserves expected to be recovered from existing wells and installed facilities (or accumulations where it would cost little to start production, when compared to e.g. the cost of drilling a well). The developed category may be subdivided into producing and non-producing. Developed producing reserves These are reserves expected to be recovered from completion intervals open at the time of the estimate. They are currently producing or, if shut-in, they were previously on production and the date of the resumption of production is known. Developed nonproducing reserves These reserves are not currently producing and either have not been on production before, or were on production before but are now shut-in with the date of resumption of production unknown. Undeveloped reserves These reserves are expected to be recovered from known accumulations where it would be expensive to start production (when compared to e.g. the cost of drilling a well). As with all sub-types of reserve, undeveloped reserves must fully meet the requirements of the reserves classification (proved, probable, possible) to which they’re assigned. Source: National Instrument 51-101 In multi-well pools, it may be appropriate to divide total pool reserves between the developed and undeveloped categories or to subdivide the pool’s developed reserves between developed producing and developed non-producing. Such divisions should be based on the estimator’s assessment of the reserves to be recovered from specific wells, facilities and completion intervals in the pool, and their respective development and production status.
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