Latest Advances in 3-D and 4-D FEM Simulation for Comprehensive Geomechanical and Geophysical Analysis of Unconventional Reservoirs, from Field Data to Numerical Models: Case Study Fm. Vaca Muerta, Argentina

Abstract

The prime goal of the comprehensive characterization of unconventional reservoirs (organic-rich mudrocks) is to build 3-D and 4-D FEM numerical models for geomechanical and geophysical studies, such as seismic full-wave propagation, AVO or AVAz analysis, seismic inversion, well stability, hydraulic fracture propagation, cement shield and casing integrity, well to well interaction, choke management for optimal well production, tests for different landing zones, fault and layer reactivation risk cubes and other geomechanical attributes. The current technologies for the acquisition and processing of seismic data, well logs and well testing such as walkaround and walkaway VSPs, multicomponent (3C) seismic, microseismic, crossed dipole sonic logs, DFITs, etc., together with laboratory core measurements and modern rock physics models allow performing a mechanical characterization of the reservoir anisotropy, its strength properties and the stress field. This work presents a 3-D/4-D orthorhombic poroelastic geomechanical model of a vertical well in the Vaca Muerta formation (Neuquén Basin, Argentina), located in the oil generation window. The developed procedure starts from a mechanical (anisotropic) and petrophysical model, including a stress field characterization; at that point the initial reservoir conditions are reproduced. Then, a full-wave propagation synthetic seismogram (wave conversion modes), an AVO and an AVAz analysis are carried out, validating the direct model built. After that, the drilling process, casing and cement shield integrity, hydraulic fracturing and well production are simulated. As shown in this paper, these types of numerical simulations allow testing different scenarios, which helps to reduce uncertainty and anticipates issues that could affect hydrocarbon production or well integrity during the exploitation of the reservoir, leading to an increase in the return on the initial investment, which in unconventional reservoirs is very high.