Abstract
Reservoir depletion and its influence on subsequent hydraulic fracture propagation are studied using a three-dimensional fully coupled geomechanics, fluid flow and hydraulic fracturing code. Pressure change and resultant stress alteration are captured through a rigorously developed poroelastic model, validated against analytical solutions. In the context of parent-child well interference, depletion-induced stress reduction will attract fracturing from nearby wells, unfavorably affecting production of the parent well in most cases by leaving the target region unstimulated or understimulated. One engineering practice to remedy this impact is to refracture the parent well before fracturing in child wells. How this treatment impacts the fracturing and to what extent it can prevent the attraction have been quantitatively studied using the geomechanics-flow coupling and hydraulic fracturing capabilities within a unified framework. Sensitivity studies of matrix permeability, production time and fracture spacing have been performed to explore the feasibility of controlled fracture growth into a depletion region. The amount of fluid required to refracture the producing well sufficiently to create a stress barrier that inhibits deletarious growth of child fractures depends on the degree of reservoir depletion. A complex scenario involving the interactions between reservoir depletion, refracturing and geologic factors such as stress barriers is also studied. The possibility for a subsequent fracturing to break through a stress barrier after a certain time of production, which would otherwise be impossible, is explored, indicating a potential parent-child well interference mechanism even when the parent and child wells are located in different formations. This phenomenon is essentially three dimensional and has not been captured by previous studies.
