RE: Comparing the Tullow SP with Brent1 Mar 2021 17:31
The below will illustrate my point on why 34% is a high figure for striking oil:
For exploration ventures, the recommended method to assess the chance of commercial success is to first identify the minimum field size associated with the firm's definition of the threshold of commerciality, and then to determine what proportion of such fields occur in the natural population of counterpart accumulations in the subject trend, play, or basin. This requires the geologist or engineer to construct a field size distribution.
Example
For a given extension project having a predicted mean reserve size of 1,500,000 BOE, the geologist has concluded that the probability of reservoir rock is 0.9, the structural probability is 0.8, and the probability of hydrocarbon charge is 0.9. The chief geological risk concerns whether a key fault will or will not seal, and the geologist assesses this as a 50/50 proposition. Thus, the perceived chance of geological success is 32%. However, construction of a field-size distribution for 20 analogous fault-separated fields in the trend reveals that only 3/4 of them are larger than 200,000 bbl, which is the minimum economic field size in this trend for your firm. Therefore, the chance of commercial success is 0.75 × 0.32 = 0.24. Calculated in this way it represents the chance of finding a field of 200,000 bbl or larger.
Hope that makes sense.