Abstract

P.T. Stanvac Indonesia routinely evaluates the likelihood of fault seal in both production geology studies and in the evaluation of exploration prospects. The oil distribution pattern in Stanvac's fields and in those of other operators has enabled us to recognize characteristics associated with sealing or leaking faults.

We construct "Allan" fault plane maps for the situations where faults appear to limit oil distribution. These fault plane maps show the vertical and lateral extent along which the reservoirs in one fault block are juxtaposed against the lithologies of the adjacent block. This demarcation of juxtaposed lithology has given us a good indication of whether these faults are sealing or leaking.

Published papers have shown that the composition of the stratigraphic section juxtaposed against a reservoir is a major factor for the capacity of the fault to cross-seal at that reservoir level. However, several examples presented in this paper will demonstrate that the structural style of faulting is also an important consideration in the sealing capacity of these faults.