The issue of filtrate cleanup in tight-gas wells following a hydraulic fracture treatment has long been a topic of discussion in the industry. At one extreme, there is the possibility of a "water block" in which filtrate fluid prevents gas production completely. In other cases, filtrate recovery can vary over a wide range, but without apparent effect on the post-fracture production. This paper describes history matching performed on a hydraulically fractured tight gas well. Fracture growth simulations were performed with a 3D fracture model, using data from a permanent bottomhole gauge for a mini-frac and propped fracture treatment. Net pressure matching during both pumping and shut-in, based on bottomhole gauge data, gave insight into fracture geometry and resulted in two different interpretations of the net pressure data. The two different net pressure matches gave propped length estimates that varied by a factor of two. A new tool automatically generated a reservoir simulator input deck with an explicit gridded representation of the fracture for both of these cases. The model generated includes all the information needed to simulate the initial post-fracture cleanup, including the filtrate invasion profile calculated by the fracture growth model.

This reservoir simulator input deck was used to history match the measured post-fracture production test data (gas rate, water rate, bottomhole pressure). To perform the match, permeability and capillary pressure curves were adjusted for the filtrate-invaded zone and for the reservoir. Initial values for the permeability came from welltest and core results, which had given very different kh estimates. The regained permeability of the proppant pack also had to be adjusted. A reasonable match of the bottomhole pressure and the water rate during the cleanup period was obtained. The history match was good enough to allow forecast runs to be made with the same model, taking into account realistic capillary pressure behavior for the fracture fluid filtrate in the formation. These forecast simulations gave useful insights into the impact of a delayed cleanup on the longterm production behavior of a tight gas well.

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