Flow Interference Between Frac Clusters (Part 2): Field Example From the Midland Basin (Wolfcamp Formation, Spraberry Trend Field) With Implications for Hydraulic Fracture Design
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2017, Unconventional Resources Technology Conference (URTeC). This study expands the high-resolution visualization of the drainage around horizontal wells using a newly developed analytical streamline simulator. A first case of single synthetic fractured well highlights the stagnation points occurring between the frac clusters, where drainage is ineffectively slow. A second synthetic case of two parallel wellbores with multiple fracture hits may enlarge the stagnant zones, with negligible drainage, occurring between the frac clusters. Finally, our flow tracking method is used to history match the total production with fracture allocated production for a multi-stage fracked well in the Wolfcamp formation, Midland basin. Progressive drainage of the SRV is visualized using the actual production data. The recovery factor after 5 years is 4% but rapidly slows and reaches only 6% after 40 years. When natural and/or hydraulically induced micro-fractures are assumed absent, only the near-frac regions in the SRV are drained even for tight frac spacing. Pressure near those fracs is rapidly lost and the productivity index of unconventional wells remains very low. Unrecovered oil remains trapped in so-called dead zones occurring in the matrix domains of extremely slow flow between the principal frac zones. Our simulation suggests that refracs between the original frac clusters can tap the oil in the dead zones after the first few years of production and may increase recovery factors and thus improve well economics. This conclusion is contingent on the assumption that the matrix domain between the fracs remains unfractured, When the matrix is micro-fractured, deeper domains would be drained (future work), leaving only residual, un-recovered hydrocarbons entrapped in the matrix blocks engulfed by the microfractures.
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Proceedings of the 5th Unconventional Resources Technology Conference
