The dilemma of soaking a hydraulically fractured horizontal shale well prior to flowback – A decade literature review.

Water soaking a horizontal shale well is a practice whereby operators in shale gas and oil production shut-in a well after a multistage hydraulic fracture treatment. By this practice, it is expected that production volumes will increase when the well is eventually opened to flow. However, there is currently no consensus on the benefits derived from this procedure. This is due to limited understanding of the subsurface mechanisms during the soaking period and their effect on both short- and long-term productivity. Also, the duration of soaking is currently chosen arbitrarily. This study reviews a decade of research (2010–2020 including January–February of 2021) in the subject area. Focus is placed on subsurface mechanisms during soaking, the fate of water-based hydraulic fracture fluids, and production performance of wells which have experienced soaking. Models describing production performance from soaking are presented and compared. It became evident from the reviewed works that the performance of soaking is affected by several factors of which soaking duration and water imbibition are the most significant. These factors can be grouped largely into fracture fluid properties, formation related parameters and operational procedures. The story of each well or field would need to be told separately when discussing soaking performace. At the same time, varying statements between operators and researchers regarding the benefits of soaking need not be considered contradictory but should be looked at on case-by-case basis. This review does not make a choice on whether to soak a well or not—it rather provides readers with research progress for the past ten years on the subject. It further narrows in on key parameters to focus on in evaluating the option to soak a well. Research directions that can contribute to the topic are also provided. • Well soaking in shale reservoirs is practiced to improve production performance. • There is currently no consensus on benefits derived from well soaking.. • Well performance with soaking is significantly affected by soaking duration and water imbibition. • The duration for soaking is currently chosen arbitrarily. • Fracture fluid properties, formation related parameters and operational procedures affect soaking performance. [ABSTRACT FROM AUTHOR]