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Triassic Fluvial Reservoir – Do You Know How to Find Your Sands?

Abstract

A successful appraisal program is the key for future field development hence having the ‘right’ well is the utmost priority and so is the data gathering. The prospect under investigation is part of a Triassic reservoir that is interpreted as a stacked channel system of about 500ft height. The channels are expected to show low sinuosity with N-S direction. Unfortunately the seismic data does not allow guidance of channels or sand distribution in any way. The lateral overall sand fraction of the prospect was deducted from the vertical sand distribution at the two wells based on VSH cut-off. Using analogue data the channel geometry was estimated from the sand thickness and the depositional environment. Several methods and strategies were applied and compared for modelling the sand distribution and the bulk volume for the radius of influence of the appraisal well. The modelling showed that only a few parameters have a major influence on the sand volume calculated for the planned well: global sand fraction, channel width and channel thickness. From this work a set of simple rules and guide lines can be derived that are applicable to many clastic reservoirs with limited well data and no additional seismic information for facies modelling: 1. Keep it simple. Often sophisticated models do not deliver added value in terms of sand distribution uncertainty and volumetric 2. Work with different scenarios estimating the global sand fraction and eventually its distribution. 3. Use Gauss Indicator simulation for investigating the different scenarios: it is quick, simple and reliable. 4. Derive object (channel) thickness and width data range from analogue. These parameters are most influential on the spread of the sand volume distribution. 5. Use MPS for building a final model – it delivers more realistic results and is the preferred option for RE.