Introduction

A decision to drill an amplitude-based prospect must be based on rigorous validation of the seismic anomaly and evaluation of the prospect risk and the potential hydrocarbon volumes. Sometimes there is strong seismic evidence that hydrocarbons are present. Even in this case, careful DHI interpretation and risking of amplitude-supported prospects can reduce the exploration uncertainty and risk and, hence, encourage drilling a wildcat well.

Direct hydrocarbon indicator (DHI) interpretation consists of two phases: (a) recognition of seismic anomalies and (b) validation of the selected anomalies. The validation requires quantitative calibration of rock properties to seismic data (Chapter 11). Prospects with seismic data that contain clear apparent anomalies, possibly indicating a hydrocarbon presence, still have to undergo careful rock-physics-based examination to ensure that these anomalies are not false indicators.

Prospects without obvious amplitude anomalies are also studied using the same worklow to estimate the seismic response from prospective hydrocarbon-bearing reservoirs. If such investigation suggests that DHIs are expected, this exploration opportunity is highly risked and seismic acquisition and processing have to be revisited. On the other hand, if the study suggests that no obvious hydrocarbon indicators are expected, the possibility of hydrocarbon-bearing rocks in this particular prospect cannot be excluded. Such methodologies have been successfully applied to quantifying the exploration risk in many amplitude-supported prospects (Roden et al., 2005; Fahmy, 2006; Forrest et al., 2010; De Jager, 2012; Roden et al., 2012).