North Sea Inter-well Flow Pattern Interpretation
In a North Sea reservoir, a significant tracer campaign was carried out to map flow and reveal communications between injectors and producers.
In a part of the reservoir dominated by fluvial channels, water was injected for pressure support through two injectors (Injector I-A and Injector I-B). Initially, the reservoir model assumed that communication along the channels was good, and that communication from channel to channel was difficult (cf. the illustration of the reservoir above).
Base model response to tracer data
Before the tracer campaign, available production data were used to verify the model assumptions. This resulted in a model able to predict the correct amount of produced water. However, the original model failed to predict the data from the tracer campaign. The simulated results from the original model show a very small tracer response (the hardly visible blue curve in the inserted enhanced view in the above figure) compared to the significant response in the true tracer production curve. The geological structures (channels) assumed in the original model can thus match the correct amount of water, but not the correct source of this water.
Tracer information improves model
From inspection of the reservoir model in the relevant region, it is natural to attempt a modification of the fluvial channels. The main problem in the original model is that water cannot flow across the channels. The channel widths were therefore increased to enable water to flow across the channels. The result of this model modification on the simulated response can be seen in the final figure above. The simulated results from the enhanced model show a significant tracer production, in agreement with the true tracer production curve.
In conclusion we note that application of Restrack’s tracer technology yields essential information about the reservoir. This information was not available in the other production data. A correct understanding of the channel structure in the reservoir was only possible by predicting the correct origin of water, in addition to the correct amount of water.
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