Development of an Optimized Completion Strategy in the Vaca Muerta Shale with an Anisotropic Geomechanical Model

Abstract

In the Vaca Muerta shale of the Neuquén basin, Argentina, the most prolific intervals tend to be the most difficult to hydraulically fracture because of the abnormally high fracture gradients present in some parts of the basin. Thus, it becomes very important to have a good understanding of the anisotropic geomechanical properties of this heterogeneous formation prior to developing the completion strategy. A calibrated, anisotropic 1D mechanical earth model (1D MEM) was developed and used to optimize the completion strategy for a vertical well in the Vaca Muerta shale. The output from the 1D MEM, including the principal stresses, anisotropic elastic properties, pore pressure, and rock strength, were used to define the reservoir intervals with the best characteristics for initiation, propagation, and maintenance of a conductive complex fracture network. Next, the reservoir intervals with the highest hydrocarbon generation tendency were determined from petrophysical and image logs acquired in the well. This formed the basis for selecting the optimum number of stages and perforation strategy for the well. Sensitivity analysis revealed the impact of the hydraulic fracture properties on the production performance. The analysis showed that higher fracture conductivity greatly improves the well performance in the deeper Vaca Muerta intervals, whereas larger fracture surface area is more beneficial across the shallower intervals. Thus, a unique completion strategy was developed for each interval to optimize the well performance. Three hydraulic fracture stages were planned initially, but because of casing limitation, only the first stage was executed. A time-lapse acoustic measurement acquired from the well corroborated the propped fracture height predicted during the completion design phase. The study showed that proper characterization of the anisotropic geomechanical behavior of the Vaca Muerta formation improves the development of a completion strategy, which ultimately optimizes economic performance of the well.

Unlocking the True Potential of the Vaca Muerta Shale via an Integrated Completion Optimization Approach

“…But the analysis indicates that the well placement relative to the stratigraphic framework may have an influence on the created fracture height growth. This behavior has been observed and documented in other shale plays in the US (Ejofodomi et al 2011).…”

“…Prior to the introduction of complex fracture models, reservoir simulation approaches have utilized dual-porosity solutions to approximate the details of the fracture network (Du et al 2009(Du et al , 2010Ejofodomi et al 2011;Mongalvy et al 2011). However, the ability to discretely grid complex hydraulic fracture geometries in reservoir simulation models is now required to provide the necessary detail to properly evaluate fracture treatment designs and well performance.…”

“…Since active development began in 2010, several studies have been published (Badessich and Berrios 2012, Monti el al. 2013, Ejofodomi, Cavazzoli et al 2013a, 2013b, Ejofodomi, Varela et al 2014 to evaluate the different completion strategies utilized and their impact on the production performance. To further improve investigations and characterize complex interactions taking place in shale plays, integration is critical.…”

Relationship between fissility, composition, rock fabric and reservoir properties in Vaca Muerta Formation (Neuquén Basin, Argentina): from outcrop to subsurface core data

“…As all shale reservoirs, Vaca Muerta Formation rocks exhibit vertical transverse isotropy (VTI rock type : Thomsen, 1986;Ejofodomi et al, 2014;Varela et al, 2020) where the elastic parameter changes with the plug orientation with respect to bedding (i.e., Ramos et al, 2019;Sosa Massaro et al, 2020), generating a variable anisotropy of the rocks. The studied rock samples characterized by high fissility index are more anisotropic than their massive counterparts (Fig.…”