Tight gas reservoir development has long been affected by 1) complex flow profiles and 2) the impact of very low permeability on reservoir productivity. Where well tests (WT) buildup is very short, interpretation becomes difficult and results often are ambiguous. Most WT of tight, dry gas wells are of short duration; thus, such tests typically lead to multiple interpretations and open-ended conclusions. Adding to the complexity, simulation software packages often fail to adequately model flow in fracture networks.

A series of well tests were conducted in tight sandstone, dry gas, naturally fractured reservoirs post-induced hydraulic fracturing. The tests were conducted for long durations: 100 hours in most cases, and 1,000 hours in two extended well-test cases. The WT responses from these tests were ambiguous.

We have investigated possible direct causes of the ambiguous results, including wellbore, geology, and specific well conditions. However, because the WT response has been found repeatedly in a variety of regions around the world, it may not be related to any of these.

After investigating in multiple manners, including the use of simulation software, we argue that the anomalies in the WT response may reflect a step in the scale-dependent properties of the fracture network.

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