Modifying the Orientation of Hydraulically Fractured Wells in Tight Reservoirs: The Effect of in-situ Stresses and Natural Fracture Toughness

Hydraulic fracturing in shale formations containing natural fractures can lead to complex and branched fracture networks which may fail to efficiently access hydrocarbons deep in the formation away from the well. In this study, to minimize the negative effects of natural fractures, the orientation of hydraulically fractured wells in such formations is investigated with the focus on the effects of in-situ differential stresses and toughness of natural fractures. To explore the impact of geomechanical properties on gas production from hydraulically fractured wells, fractures were first up scaled and then gas production from the reservoir was investigated. The results show that low natural fracture toughness and differential in-situ stress both increase the tendency of propagating hydraulic fractures to exploit natural fractures. Under these conditions, it was found that drilling the well in a modified orientation could result in a higher recovery factor compared to the wells drilled parallel to the direction of minimum horizontal stress. This is due to the larger stimulated reservoir volume through a synergy between the hydraulic and natural fractures. However, high differential in-situ stress and fracture toughness both lead to a transition from this tendency, in which hydraulic fractures cross natural fractures rather than exploiting them. As a result, changing the well orientation in these scenarios are less efficient than the industry standard. The results of this study demonstrate a window of geomechanical scenarios in which changing well orientation is beneficial, can be produced as a fast-screening method for engineers to determine the optimised well orientation.