Most multiple-transverse-fracture horizontal wells in shale-gas formations remain in transient bilinear or linear flow for very long periods. However, there are often reported cases of shale wells that exhibit boundary-dominated flow in a very short period, which implies a stimulated rock volume (SRV) much smaller than would be expected. This paper offers an alternative explanation for the early boundary-dominated flow related to dissolution of salt-sealed natural fractures in the shale.
Operators producing gas from the Haynesville, Marcellus, and Horn River shale formations have observed that produced water is more saline than the injected fracturing fluid. Additionally, the fraction of injected water that flows back when the well is put on production—termed load recovery—is low.
This study investigates the possibility that salts removed by flowing back injected low-salinity water-based fracturing fluid may be a mechanism for increasing the effective permeability in shale-gas wells within a limited volume surrounding the created hydraulic fractures. The study offers strong evidence that salt may be a key factor in productivity and ultimate gas recovery from shale-gas wells....
Model for a Shale-Gas Formation With Salt-Sealed Natural Fractures
20 September 2016