A sudden change in flow in a confined system results in the formation of a series of pressure pulses known as a water hammer. Pump shutdown or valve closure at the conclusion of a hydraulic fracture treatment frequently generates a water hammer, which sends a pressure pulse down the wellbore that interacts with the created fracture before returning towards the surface. The result is a pressure profile that consists of a series of oscillations that attenuate over time due to friction. Hydraulic fracture treatments have been shown to alter the period, amplitude, and duration of the water hammer signal. The goal of this study was to history match water hammer data from several multi-stage fractured wells with simulations derived from a water hammer model and compare the results to gathered production log and microseismic derived stimulated reservoir volume (SRV) data.

Water hammer pressure signals were simulated in this study with a numerical model that combined the continuity and momentum equations of the wellbore with a created hydraulic fracture represented by a circuit with a resistance, capacitance, and inertance (R, C, and I) connected in series. Treatment pressure data from three horizontal fractured wells were history matched with the numerical model by iteratively altering R, C, and I until an appropriate match was obtained. All three horizontal wells had both production log and microseismic data for each stage, and the R, C, and I values obtained from history matching were compared to production log (gas) and microseismic SRV for any correlations.

It is shown that the water hammer derived capacitance was directly correlated with the stimulated reservoir volume (SRV) derived from micro-seismic measurements, however, it showed no correlation with gas production obtained from the production log. Inertance also showed a positive correlation with SRV but had no correlation with production log data. Finally, the water hammer derived resistance exhibited no correlation with SRV data, but showed a positive correlation with gas production.

The results from this work support the fact that the water hammer signal at the conclusion of a hydraulic fracturing treatment stage, contains diagnostic information about the created fracture network. Since this data can be recorded at very little incremental cost, it may prove to be a very useful and cost effective fracture diagnostic tool.

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