Identification of water-cut dynamics in a producing well after breakthrough of a water-induced fracture

Water-induced fractures created during water injection can connect injection and production wells. However, the fraction of produced water often increases significantly only after an initially moderate response following breakthrough. We hypothesize that this delayed acceleration is due to time-dependent leakoff through the fracture walls. Suspended solids are deposited and form a filter cake, gradually reducing wall permeability that increases the fraction of injected water delivered to the producing well. Modern leakoff models explicitly relate leakoff to growth of filter cake and the dynamic effects of transverse flow. We formulate a reduced one-dimensional model for an extant fracture that connecting two wells. Poiseuille law describes flow along the fracture for a slot taken into account distributed leakoff proportional to the pressure difference between the fracture and the formation. We introduce fouling as a time-increasing resistance to leakoff, consistent with filter cake and skin formation concepts widely used in fluid losses modeling. The reduced form yields an explicit expression for the fraction of injected water that enters the producing well. This explicit directly correlates to the predicted water-cut at a constant liquid rate. An example for a West Siberian field reproduces a common observation: the water-cut rises from ~30% at breakthrough to >90% within ~3 months without changes in well operating conditions. We also discuss why producing wells act as attractors for the trajectories of slowly propagating injectioninduced fractures due to poroelastic stress perturbations, and why a wellbore can arrest a fracture after intersection. This behavior agrees with fracture – well interaction in the framework of "stophole" fracture mechanics

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