The efficiency of hydraulic fracturing operations can be significantly impaired by multiple damage mechanisms induced by the fracturing fluid, that affect both the formation and the proppant pack. The two key damage factors are
unbound immobile water trapped in pores preventing the flow of hydrocarbons and
insoluble polymer residue originating from degraded fracturing fluid gelling agents.
This study aims at elaborating on the mechanisms of the fluid-related damage and on new solutions to mitigate their detrimental effect.
On the modeling side, a commercial reservoir-centric stimulation-to-production software was used to study the impacts of fracture network conductivity and effective fracture length/ area on simulated well production. On the experimental side, a comprehensive study of a gelling agent degradation mechanism and the formation/ proppant pack dewatering process was performed. A new experimental setup was developed, focused on relative oil/ water permeability measurements in mixed packs of proppant and rock.
An extended sensitivity analysis of production for different fracturing job types (slickwater and crosslinked) was conducted for a major US play, the Eagle Ford shale. The effects of fracture geometry and conductivity on initial and cumulative production were quantified. These reveal general trends and enable further job design optimization for a variety of parameters. Several concepts were tested in the laboratory targeting improvement of effective fracture geometry through minimization of polymer residue and reduction of water saturation. The selected concepts enabled development of a new highly effective multifunctional chemical additive. The performance of this additive was further validated in application-oriented testing.
This paper investigates the impact of prominent damage mechanisms on well production and proposes solutions for damage mitigation. The results demonstrate how the combined approach relying on production simulations and laboratory development can be used to optimize well performance.
Although the primary goal of hydraulic fracturing is to create a highly conductive flowpath, numerous damage mechanisms can reduce the effectiveness of the stimulation treatment. A major damaging factor is fracture exposure to large quantities of water-based fluids. Typically, only up to 30﹪ of the treatment water is recovered during flowback operations; the residual water remains in the fractures or in the rock matrix immediately surrounding the fracture network (Pagels et al. 2013). As a result, water blocks are formed when the pressure drawdown fails to exceed the capillary pressure, which is particularly recurrent in low-permeability reservoirs (Bazin et al. 2010). Optimized surfactants are necessary to mitigate these effects (Sethi et al. 2015). They decrease capillary pressure by surface tension, interfacial tension, and contact angle effects, which improves the relative permeability to hydrocarbons in the near-fracture formation. In many cases, this results in better well performance (Khvostichenko and Makarychev-Mikhailov 2018).