Parameters Effecting the Interaction among Closely Spaced Hydraulic Fractures

Abstract

Placing multiple hydraulic fractures at intervals along horizontal wells has proven to be a highly effective method for stimulation. However, the mechanical interaction between a growing hydraulic fracture and one or more previous hydraulic fractures can affect the fracture geometry such that the final fracture array is suboptimal for stimulation. If the fracture array geometry is idealized as a set of regular and planar fractures, history matching and production forecasting may be inaccurate. During the treatments, the fractures can curve towards or away from one another, potentially intersecting one another. A detailed parametric study of this phenomenon using a coupled 2D numerical fracturing simulator shows that the curving is associated with a combination of opening and sliding along the previously placed hydraulic fracture, as well as the previous fracture's disturbance of the local stress field because of its propped width. Dimensional analysis and scaling techniques are used to identify the key parameters that are associated with suppression of each mechanism that can lead to hydraulic fracture curving. The analysis, which is in agreement with available data, results in a clarification of the conditions under which attractive and repulsive curving are expected, as well as the conditions under which curving is expected to be negligible or even completely suppressed. This last case of planar hydraulic fracture growth is of practical importance and will usually be considered desirable. We present a straightforward method for determining whether planar fracture growth is expected that additionally gives insight into how design parameters can be modified to promote planar hydraulic fracture growth.

Interference Fracturing: Nonuniform Distributions of Perforation Clusters That Promote Simultaneous Growth of Multiple Hydraulic Fractures

“…Of course this assumption must be carefully evaluated because the same stress shadow that can suppress growth of some fractures will also cause the paths of most, if not all, fractures in the array (depending on symmetry) to be deflected. Here we justify the planar assumption, albeit tentatively, based on a previous numerical, laboratory, and minethrough study showing that arrays of sequentially-placed hydraulic fractures under realistic reservoir conditions can grow with small enough deflection that it can usually be neglected at the relevant scale of the problem (Bunger et al 2011, 2012, Kear et al 2013. That being said, simultaneous growth is expected to produce more complicated interactions because of the ability for the growing fracture tips to interact (Sesetty and Ghassemi 2013), and the assumption of planarity embedded in the present model must therefore be examined in detail in future work.…”

Numerical methods for hydraulic fracture propagation: A review of recent trends

“…• Experiments showing growth of curving hydraulic fractures in the presence of a nearby free surface (Bunger et al, 2004; and/or in the vicinity of a nearby, previously-placed hydraulic fracture (Bunger et al, 2011). Numerical simulations have been shown to capture the behavior of these experiments , with the notable observation that hydraulic fractures curve towards a free surface in all cases but can curve towards or away from previously-placed hydraulic fractures depending on the magnitude of the minimum confining stress.…”

Dependence of Static Fatigue Tests on Experimental Configuration for a Crystalline Rock

“…The quarry for the material is located at Black Hill, about 100 kilometers North East of Adelaide in South Australia [13]. This material has been utilized in a range of experimental campaigns [14], [15] and the (static) mechanical properties have previously been characterized as presented in Table 1. …”