In an unconventional tight oil play with natural fractures, the main drive mechanisms are depletion above the bubble point and compaction. They are not easily recognized yet play a major role in diminishing performance. An extensive integrated study, using the Event Solution approach, of a Mid-continent naturally fractured tight oil carbonate resource was undertaken to examine the causes of performance variability. The integrated study included a thorough petrophysical and fluid characterization. Drive mechanisms were associated with specific rock types and in relation with fracture density, explaining performance characteristics. Extensive numerical simulation was used to combine characterization and historical performance. Initially the dominant drive mechanisms are depletion and compaction. Later, gravity drainage plays a significant role but its benefits are not captured with the initial well designs. Previously, wells were placed at the top of the reservoir and hydraulic fractures extended downwards. The study concluded that applying a different well type, multi-laterals extended both laterally and stacked vertically, can leverage on gravity drainage. An innovative well design was implemented to capture the benefits of multiple drive mechanisms. Additionally, the optimized operating conditions were identified to maximize impact. As a result, it is possible to increase recovery efficiency at a lower capital and operating cost. The learnings from this project can benefit the continued development and also serve as a paradigm in the very important tight oil plays in North America, which are largely carbonate with various degrees of natural fracturing.

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