Like any unconventional resource, the economic viability of the Vaca Muerta shale, located in the Neuquén basin, Argentina, depends on the ability to effectively connect the tight rock fabric to the wellbore by creating complex fracture networks. This requirement makes the completion strategies and hydraulic stimulation treatments critical to the economic success of the unconventional reservoirs.
This paper presents a brief review of the Vaca Muerta and identifies the dominant challenges across the basin. To provide a full understanding of the impact of these challenges on the well performance, several simulations were carried out with a comprehensive software package that efficiently enables full-cycle seismic-to-reservoir simulation of unconventional reservoirs. The software handles the impact of structural and property heterogeneity, differential horizontal stress anisotropy, and natural fractures in the formations, all of which influence the creation of complex hydraulic fractures in the Vaca Muerta shale. The software also enables specialized, automated gridding of the modeled complex hydraulic fractures for reservoir simulation, preserving the actual fracture geometry " footprint" while performing the numerical reservoir simulation.
The Vaca Muerta shale was broken down into three sections (upper, middle, lower) and a parametric study was performed to qualify and quantify the impact of the overall completion design on the actual well performance across each section. The completion parameters investigated included fluid types and volumes; pad volumes; proppant types, volumes, and concentrations; pump rate; fracture degradation (formation embedment and crushing), etc. The impact of geological and geomechanical parameters, though investigated, are not presented.
The results of the study show the different sections of the Vaca Muerta shale are impacted in different ways. For example, the hydraulic fracture conductivity has a greater impact across the lower section than the upper section. This is primarily due to the higher clay volume, pore pressure, and stress, which result in higher proppant embedment and crushing. Overall, the results provide a detailed, quantitative evaluation of the critical parameters affecting Vaca Muerta shale completions and act as a guide in developing an optimized completion program.