Applications

Challenge

Shell needed to know whether deep and shallow seismic amplitude anomalies represented commercial-scale hydrocarbon reservoirs.

Application

Three reservoir models were developed, each consistent with seismic observations: (1) a deep and a shallow hydrocarbon-filled reservoir; (2) only a deep reservoir containing hydrocarbons; and (3) an intermediate model.

An EM response was modelled for each scenario (see Figure), and a seabed-logging survey was conducted to measure the actual EM response.

Result

The measured response matches reservoir model 2. On this basis, EMGS predicted that only the deep seismic-identified prospect was a commercial-scale hydrocarbons reservoir.

This prediction was verified by an exploration well. The shallow amplitude anomalies are now thought to be caused either by residual hydrocarbons or stratigraphic changes.

EM response curves: the modelled response for (1) a deep and a shallow hydrocarbon-filled reservoir (blue curve), (2) a deep hydrocarbon-filled reservoir (orange curve), and (3) an intermediate situation (grey curve); and the EM response measured during a seabed-logging survey (green curve).