Hydraulic-Fracture Propagation in a Naturally Fractured Reservoir

Abstract

Summary We present the results of numerical modeling that quantify the physical mechanisms of mechanical activation of a natural fault because of contact with a pressurized hydraulic fracture (HF). We focus on three stages of interactions: HF approaching, contact, and subsequent infiltration of the fault. Fracture interaction at the contact is shown to depend on four dimensionless parameters: net pressure in the HF, in-situ differential stress, relative angle between the natural fault and the HF, and friction angle of the natural fault. A numerical model based on the displacement discontinuity method (DDM) allowing for fracture closure and Mohr-Coulomb friction was used to calculate the displacements and stresses along the natural fracture as a result of the interaction with the pressurized HF. The analysis of the total stress state along the fault during the HF coalescence stage makes it possible to define a criterion for reinitiation of a secondary tensile crack from the natural fault. We show that the most probable location for tensile-crack initiation is the end of the open zone of the fault where the highest tension peak is generated by the HF contact. In our numerical analysis, we study the magnitude of maximum tensile stress and its position along the fault for a wide range of key dimensionless parameters. Given real reservoir properties, these measurements can be used to detect the possible fracturing scenarios in naturally fractured reservoirs. Using simplified uncoupled modeling of fluid penetration into the fault after the contact with the HF, we demonstrate that either an increase or a decrease of the tensile stress at the opposite side of the fault can be realized depending on the ratio of increments of net pressure and the fluid front as it penetrates the natural fault.

The Fracturing Behavior of Tight Glutenites Subjected to Hydraulic Pressure

“…Geostress has been confirmed by numerous studies to be a key factor dominating HF propagation [32][33][34][35][36]. Stress anisotropy is crucial for fracturing treatment optimization because HFs always prefer to propagate in the maximum principal stress direction.…”

Characterization of Bedding-Parallel Fractures in Shale - Morphology, Size Distribution and Spatial Organization

“…Because these features are so large-comparable to the dimensions of beds-their presence may impact fluid flow in hydrocarbon reservoirs (Curtis, 2002;Chen et al, 2009;Ding et al, 2011;Duhalan et al, 2013;Zanella et al, 2015). Beef may also influence the propagation of hydraulic fractures, which are needed to stimulate production in shale (Zhang et al, 2007;Chuprakov et al, 2011Chuprakov et al, , 2013Chuprakov et al, , 2014Chuprakov et al, , 2015. Natural, sealed bed-parallel fractures may facilitate horizontal growth of hydraulic fractures by acting as planes of weakness or modulus contrast that enhance the already marked strength anisotropy due to beddingparallel laminae and planar fabric.…”

The role of rock joint frictional strength in the containment of fracture propagation

“…Some studies have been conducted to understand the effect of discontinuities on some aspects of fracture behaviour [4,15,16,22,25,27,37,66,72,81,82,85,90,92,98,99]. The influence of important variables such as the net pressure at the fracture or faults, differential stress, angle of inclination of natural fracture and rock frictional coefficient is considered in Chuprakov et al [25]. In Blair et al [15], an alternative technique for monitoring fracture growth using tracking wires was applied to observe the interaction of fractures at interfaces using pressure history records, while in Casas et al [22], fracture behaviour at interfaces with different physical and material properties was observed to determine the effect of interface properties on the extent and pattern of fracture growth.…”