Numerical simulation of simultaneous hydraulic fracture growth within a rock layer: Implications for stimulation of low-permeability reservoirs

Multi-stage multi-cluster hydraulic fracturing is currently the most effective method to stimulate low-permeability hydrocarbon reservoirs. The desired result of this stimulation technique is highly uniform growth of multiple closely-spaced hydraulic fractures. In order to deepen our understanding on the competitive growth of these fractures, we have investigated the growth behaviors of multiple hydraulic fractures under different conditions. A fully-coupled model with a 3D influence coefficient is presented for fracture growth in a rock layer, based on a combination of boundary element method and finite volume method. It is validated against classic solutions and lab experiments. The parametric analyses of dimensionless arguments to quantify the uniformity of fracture growth are performed, with varying fracture geometries and geotechnical conditions including pre-existing natural fractures. The results demonstrate that fracture competition is controlled by the dimensionless toughness, the initial fracture geometric settings and the ratio of fracture spacing to height. A higher fluid viscosity, a smaller initial length offset and a larger spacing benefit simultaneous fracture growth for conventional bi-wing hydraulic fractures. By contrast, single-wing ones exhibit a remarkably better performance in long-time simultaneous fracture growth at a small separation, especially at low dimensionless toughness. Under certain conditions, the closely-spaced single-wing fractures are prone to grow simultaneously and uniformly in less energy consumption. Their simultaneous growth is found to be insensitive to the interference from small-scale natural fractures. The uniform single-wing fracture growth from the perspective of geomechanics will provide a new insight for both reservoir stimulation and formation of vein and dike swarms.

Fig.4-Fig.16: The eps source files of figures for all numerical simulation results (vector figures) in the publication.

Results data.zip: The mat files (binary data for Matlab) of the simulation results for numerical examples in the publication, including a txt file for explaining definitions of result parameters in mat file.

The visualization of these data will be update in the following.