Parametric effects on fracture geometries from multi-fracture propagation emanating from neighbouring wellbores in quasi-brittle rocks

Abstract

An integrated approach is presented using field data input from measured geological information into numerical simulation for understanding effects of induced stress on geometries of multiple fracture propagation. We establish a benchmark study based on comparison of field result with numerical computations. The comparison then acts as reference measures for studying effects of changing in-situ stress, fracturing fluid viscosity and fracture spacing on propagation and geometries of multiple fractures between neighbouring wellbores in an undisclosed gas field. This leverages understanding of more complexities associated with inter-well multiple fracture growth that are idealized as straight from certain perspectives. Although some studies focus on stress interference from pre-existing fractures, actual fracture propagation geometries may be far from the idealized scenarios. Therefore, the stress shadow effects between growing multiple hydraulic fractures, if not taken into account, can lead to unrealistic estimation of hydraulic fracture trajectories. Consequently, more attention should be paid to the actual propagation of hydraulic fractures. Actual field geologic information is provided through well-logging and field mapping data. Very short fractures were propagated in these wells before the operation was terminated due to technical problems. The reservoir depth in the area is about 2170 m. At such depth, quasi-brittleness of shale should be accounted for by using relevant methods that capture rock ductility such as traction separation law. Abaqus commercial software is used to conduct the numerical computation using extended finite element method based on cohesive zone modeling. Application of this technique is further validated using Kristianovich-Geertsma-de Klerk analytical solution. This study is important in field implementation of infill drilling with well-informed mechanism of fracture interference in the inter-well region.