Computer simulation of hydraulic fracturing using finite elements of high aspect ratios
Pedro Rogério Cleto1; Osvaldo Luís Manzoli2; Michael Andrade Maedo1; Leonardo José do Nascimento Guimarães3
1 Department of Mechanical Engineering-UNESP-Bauru/SP; 2 Department of Civil Engineering-UNESP-Bauru/SP; 3 Department of Civil Engineering-UFPE-Recife/PE
doi:10.20906/CPS/COB-2015-1183
Resumo
The extraction and production of shale gas has gained space in the oil industry in recent years due to its economic viability. However, the shale permeability is low, fact that complicates the extraction of gas. Hydraulic fracturing is a technique capable to increase the permeability of the shale by injecting fluid at high pressure into the well. This work contributes to the generation of numerical tools to study the formation and propagation of the fractures generated hydraulically, considering a hydro-mechanical coupling explicit type. Fractures are modeled through the Mesh Fragmentation Technique (MFT), which consists in inserting nonlinear solid finite elements of high aspect ratio in the interfaces between elements of the original mesh. The fluid behavior is described by Darcy's Law. Some numerical analyses of leak-off tests in 2D wells are carried out considering different boundary conditions and types of meshes. The results show that the MFT is able to reproduce fracturing process in accordance with experimental results, presenting the pressure drop due to the hydraulic fracturing process. As expected, the fractures propagate perpendicular to the smallest principal stress in all cases. Since the fractures must follow the interface elements, surrounding the standard elements, the use of unstructured meshes is recommended to avoid mesh dependence.
Palavras-chave: hydraulic fracturing; hydro-mechanical coupling; mesh fragmentation