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  9. Discussion & Conclusion

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- I introduced this series of modules on heterogeneity in naturally fractured reservoir performance by talking about guilt and absolution. And I'd like to return to those themes now. First guilt. The place we get guilt is our difficulty in predicting NFR performance when indeed it's our job to predict performance of reservoirs. However, NFR's present a particular challenge. Heterogeneity in productivity is a consequence of: fracture-well intersection probabilities, fracture size variability, geologically induced heterogeneity such as stratigraphic and rock-property control of fracture character, diagenesis leading to both enlargement and/or occlusion of fractures. And fracture connectivity variability caused by multiple fracture sets or by variation in density of fracture sets. The place that we find absolution is to use our knowledge of fracture systems to try to improve the odds. And this can be addressed in several ways. In the drilling and completion process when we're looking for appraisal of NFR's we need to drill more wells to assess well performance distribution asymmetry. In other words, we need to know what the shape of that distribution curve is for productivity of wells. So more wells than in a conventional reservoir. We should deviate wells, or hydrofracture them, to try to improve the odds of intersection between our wellbore and the natural fracture system. We should do open hole completions. I haven't talked talked about that in these modules, but what we know is usually it's just a few fractures that flow into our wells. And we don't know when in advance which fractures it's going to be. So we don't want to cement them off behind casing and then maybe hope to get them back open again. Better try to do open hole completions if possible in NFR's. In terms of characterization, we need to integrate data from multiple sources, both dynamic and static sources of data. To try to enlarge and refine our sample volume. In other words, to transcend representative elemental volume limitations that we certainly will deal with. So anything we can do to improve our understanding of that volume will be beneficial. We need to learn from outcrop analogs. And remember that predicting performance of individual wells is just generally not possible. So it's best to maintain your humility when trying to predict well performance in an NFR. I'd like to conclude by saying that NFR's are unpredictable because of the discontinuous nature of fractures. And suggest that NFR's present a game of chance. And the best we can do is to try to understand the odds through knowledge of natural fracture systems. And try to play them in our favor. Thanks very much. I've enjoyed talking with you about one of my favorite topics, naturally fractured reservoirs.