Yamina E. Aimene

Geomechanical modeling of hydraulic fractures interacting with natural fractures — Validation with microseismic and tracer data from the Marcellus and Eagle Ford

AbstractWe have developed a new geomechanical workflow to study the mechanics of hydraulic fracturing in naturally fractured unconventional reservoirs. This workflow used the material point method (MPM) for computational mechanics and an equivalent fracture model derived from continuous fracture modeling to represent natural fractures (NFs). We first used the workflow to test the effect of different stress anisotropies on the propagation path of a single NF intersected by a hydraulic fracture. In these elementary studies, increasing the stress anisotropy was found to decrease the curving of a propagating NF, and this could be used to explain the observed trends in the microseismic data. The workflow was applied to Marcellus and Eagle Ford wells, where multiple geomechanical results were validated with microseismic data and tracer tests. Application of the workflow to a Marcellus well provides a strain field that correlates well with microseismicity, and a maximum energy release rate, or J integral at each...

Simulation of transverse wood compression using a large-deformation, hyperelastic–plastic material model

Abstract Transverse compression of wood is a process that induces large deformations. The process is dominated by elastic and plastic cell wall buckling. This work reports a numerical study of the transverse compression and densification of wood using a large-deformation, elastic–plastic constitutive law. The model is isotropic, formulated within the framework of hyperelasticity, and implemented in explicit material point method (MPM) software. The model was first validated for modeling of cellular materials by compression of an isotropic cellular model specimen. Next, it was used to model compression of wood by first validating use of isotropic, transverse plane properties for tangential compression of hardwood, and then by investigating both tangential and radial compression of softwood. Importantly, the discretization of wood specimens used MPM methods to reproduce accurately the complex morphology of wood anatomy for different species. The simulations have reproduced observations of stress–strain response during wood compression including details of inhomogeneous deformation caused by variations in wood anatomy.

Modeling Multiple Hydraulic Fractures Interacting with Natural Fractures Using the Material Point Method

This paper describes use of the Material Point Method (MPM) for modeling the propagation and interaction of multiple hydraulic fractures (HF) with natural fractures (NF). First the method is used on a laboratory experiment involving one HF and one NF positioned at different angles from the maximum horizontal stress. Various geomechanical simulations are performed by varying the stress anisotropy and the angle of the NF to study the remote impact of the HF on the NF. The results show the various levels of influence a HF has on a NF with a general trend being a higher influence for lower anisotropy ratio and lower NF angles. For an anisotropy equal to 1 and a NF with angle of 90 degrees, the detailed NF opening mechanism before, during and after the HF crosses a NF is studied in detail. The MPM simulations show that under the influence of the HF, the NF opening starts before the HF reaches it and even before the HF propagation. This result could help better understand the microseismic events recorded farther from the HF tip. Finally, a new workflow that integrates geophysics, geology, geomechanical simulations using MPM and completion engineering is described and validated with a real and complex Marcellus gas shale well. The workflow uses a seismically derived fault attribute map as input into the Continuous Fracture Modeling (CFM) approach to generate an Equivalent Fracture Model (EFM). The MPM geomechanical simulation of multiple hydraulic fractures propagating in the input EFM model leads to estimation of a strain field and J integral at each frac stage with a computation time not exceeding a few hours. The application of this workflow to an anomalous Marcellus gas well, shows that the estimated strain model has many striking similarities with the interpreted microseismic. The shape and the extent of the geobodies seen in the simulated strain field are very similar to those seen in the microseismic. Furthermore, the predicted J integral at each frac stage is correlated well with the density of the microseismic events at the same frac stage. The entire workflow takes only few hours thus making it suitable for any completion engineer designing his well. The new workflow brings improved and realistic geomechanics into the G&G world by providing new insights into the complex behavior of multiple hydraulic fractures propagating in a naturally fractured reservoir. This new insight will provide an additional powerful tool for an integrated approach that combines G&G, geomechanics and engineering for the imaging of sweet spots and reliable estimates of well performance thus allowing improved and economical fracing and development of shale reservoirs.

Using geomechanical modeling to quantify the impact of natural fractures on well performance and microseismicity: Application to the Wolfcamp, Permian Basin, Reagan County, Texas

AbstractWe have evaluated workflows to quantify the mechanical impact of natural fractures (NFs) on the production performance of hydraulically stimulated stages in shale wells. Variations in fracture orientation and density can enhance or degrade the transport and effectiveness of fracturing fluids. Specifically, we studied the effect of a complex fault splay system on a horizontal Wolfcamp B reservoir well. A general workflow that combines geophysics, geology, and geomechanics (3G) was evaluated and applied to the well. The benefits of the 3G workflow are threefold. First, the quantitative impact of the NFs on the regional stress is provided through the differential horizontal stress variation, which impacts fracturing complexity. Then, the reservoir strain map, validated with microseismic data, gives insights into the stimulated drainage pathways. Finally, the ability of the J integral to predict poor hydraulic fracturing stages as a function of fracture density along the wellbore or as a function of t...