Predicting reservoir-scale faults with area balance: application to growth stratigraphy

A reservoir that appears to lack faults at one scale of resolution or at one sampling density may nevertheless contain faults that are below the resolution of the observations. The area–depth relationship from a balanced cross-section is shown to contain the necessary information for predicting the sub-resolution fault heave. Existing area–depth theory is extended to include growth units, allowing structural length and thickness changes to be separated from the depositional changes. The technique is validated with a numerical model of a growth full graben and a sand-box model of a half graben; then field tested in the Gilbertown graben, a growth structure within the regional peripheral fault trend along the northern margin of the Gulf of Mexico. A cross-section developed from wells alone is used to infer the abundance of sub-resolution faults by the area-balance technique. A small but significant amount of sub-resolution extension is predicted and then confirmed with a high-resolution seismic line.