Karoon Gas Australia Ltd., Melbourne, has issued revised estimates for contingent resources in its Echidna and Kangaroo oil fields in the Santos basin offshore Brazil.
The new figures are based on a statistical aggregation of the three reservoirs—Paleocene-A, Paleocene-B, and Maastrichtian—rather than the arithmetic addition method used in its previous estimates in September 2015.
Karoon now believes that the individual reservoirs should be aggregated using probabilistic addition rather than arithmetic addition because oil-in-place reservoir parameter inputs are largely independent for each reservoir across both fields.
However, the company adds that the key inputs of GRV, OWC, and NTG are judged to have some degree of dependency between reservoir units and have been assigned 40-60% positive dependency.
Karoon says the level of certainty in the contingent resources is now much greater.
For Echidna the May statistical aggregation estimates are 30 million bbl (1C), 55 million bbl (2C), and 92 million bbl (3C). This compares with the published 2015 estimates of 25 million bbl (1C), 75 million bbl (2C), and 152 million bbl (3C) using the arithmetic method.
For Kangaroo the May statistical aggregation estimates are 16 million bbl (1C), 27 million bbl (2C), and 46 million bbl (3C) compared with the 2015 published arithmetic estimates of 20 million bbl (1C), 54 million bbl (2C), and 100 million bbl (3C).