Sathish Sankaran

Fracture Geometry and Vertical Migration in Multilayered Formations from Inclined Wells

Knowledge of the near-well fracture geometry and the connection with the ultimate fracture propagation are of great importance to hydraulic fracture design. This is particularly true in high-permeability reservoirs where the connectivity between the well and the fracture has been viewed as a critical element to the success of the well stimulation. In addition to the fracture geometry difficulties, fracture height migration, that is the vertical fracture growth outside of the target interval is, invariably, an undesirable occurrence (unless the fracture is designed to penetrate a multi-layered formation.) When the fracture propagates through adjoining-to-the-target layers, there arises an impending danger of proppana screen-out leading to excessive pressurization and subsequent te mination of the process. Therefore, it is essential to control and contain a hydraulic fracture within its target layer and to minimize geometry complexities in the near-well zone. Because inclined wells are drilled frequently in the petroleum industry, this work aims at developing a model for predicting fracture migration heights and the crack paths in multi-layered formations penetrated by such wells. The dependence of fracture initiation conditions on well inclination and mechanical properties are used to predict the migration of fracture height into adjacent layers using fracture mechanics models. The model predictions can be used beneficially in planning hydraulic fractures and in anticipating fracture geometry, thus, providing drilling trajectory guidelines. By controlling the fracturing fluid pressure gradient it is possible to affect the fracture geometry. A multi-layer approximation approach is presented to provide a formulation of the inclined well problem. The effects of well inclination and stress contrast on fracture height migration are studied and guidelines are offered on the desired well trajectories in view of property contrasts among layers for acceptable fracture geometries.