Mohamed, I. M. (Advantek Waste Management Services) | Algarhy, A. (Advantek Waste Management Services) | Abou-Sayed, O. (Advantek Waste Management Services) | Abou-Sayed, A. S. (Advantek Waste Management Services) | Elkatatny, S. M (KFUPM)
ABSTRACT: Slurry waste management may involve injection of solid-laden fluids with concentration up to 25%. To accomplish this without plugging the near wellbore pore space, a fracture is created first using a pad of clean fluid. In some cases, where the formation has a high permeability-thickness product, kh, high injection flow rate is needed to open up the fracture with clean fluids. Most disposal wells do not have large enough pumps to provide the needed flow rates. A combination of a lack of geomechanical understanding combined with poor injection or facility design leads some operators to create high formation damage around their wellbores in slurry injection applications by injecting slurry at flow rates which are insufficient to open fractures. Moreover, the damage causes injection pressure to build up rapidly, facilitating the creation of short fractures which tend to cause near wellbore stresses to increase more rapidly for a given amount of solid deposition than is the case with longer fractures. This paper presents one case study which evaluates the injection well using operational data.
Slurry injection emerged in the late 1980’s and is one of the major environmental and economic methods of waste disposal management (Abou-Sayed et al., 1989; Moschovidis et al., 1998). In slurry injection, solids are slurrified with suitable carrying fluid (e.g. fresh water, produced water, or sea water) (Willson et al., 1998; Moschovidis et al 1999). The slurrified wastes are then injected into an underground permeable formation (Marinello et al., 2010). To provide the maximum possible storage space for the wastes, a porous formation that meets specific criteria is hydraulically fractured (Abou-Sayed and Guo, 2001). One of these criteria is a sufficient permeability to allow the liquids to leak off into the formation through the fracture faces (Van den Hoek, 2002).
During water injection, hydraulic fractures might intentionally or unintentionally be created (Morales, et al, 1986). During matrix injection of water, the permeability of the near wellbore region might decline (formation damage) by the accumulation of the suspended solids in the injected water to form internal and external filter cake (Bennion et al., 1996). The formation damage accumulation will cause the injection pressure to increase (Abou-Sayed et al., 2007). Once the pressure increases to a point that exceeds the formation fracture pressure, a hydraulic fracture will be unintentionally created (Elkatatny et al., 2017). The created hydraulic fracture will enhance the well injectivity and a sudden drop in the injection pressure will be observed (Abou-Sayed and Zaki, 2005). Unlike water injection operations, creating a hydraulic fracture is essential for a successful slurry injection project (Abou-Sayed et al., 2002; Majidaie and Shadizadeh, 2009).