Introduction

This chapter focuses on the specific role of amplitude interpretation for the purpose of reservoir evaluation. A number of techniques based on seismic amplitude have been described in previous chapters, including AVO analysis and various inversion techniques, and the interpreter's choice will depend to a large extent on the quality and type of data available as well as the problem at hand. In general, relative techniques, such as AVO analysis for defining fluid related anomalies, are appropriate in the exploration phase whereas in development projects more sophisticated techniques requiring significant well control, such as deterministic and stochastic inversion, are warranted. At each stage the interpreter can attempt to use seismic amplitude to describe the critical aspects of the reservoir as well as defining limits of uncertainty. It should be noted that to be consistent with the aim of the book in terms of the physical interpretation of seismic amplitude, purely statistical or ‘data mining’ type techniques have not been included in the discussion.

In field development, seismic interpretation is an integral part of the field geological model; key reservoir parameters that can be characterised include geological facies, reservoir properties (including porosity, net-to-gross and water saturation) and reservoir geometry and connectivity. In addition to the static element of the reservoir, time-lapse seismic offers the chance to evaluate dynamic changes. Seismic amplitudes also have a central role in the risk evaluation of prospects characterised by DHIs. In addition, modern amplitude technologies can produce results with reasonable certainty such that they can be incorporated into the process of reserves determination.