Parameters Affecting the Interaction Among Closely Spaced Hydraulic Fractures

Abstract

Summary: Placing multiple hydraulic fractures at intervals along horizontal wells has proved 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 toward 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.