The formation evaluation of low-porosity tight gas reservoirs in Argentina presents several well-known challenges in the estimation of main petrophysical properties as porosity, clay fraction, permeability, and water saturation. The main goal is to accurately quantify these petrophysical properties with a consistent and reliable petrophysical model. The next task is to reveal the key petrophysical responses that represent the link between petrophysics and production. The present work describes the main petrophysical challenges faced and an innovative workflow used in the Lindero Atravesado field with clear examples to illustrate the effectiveness of this approach. The workflow involves measurements such as advanced elemental gamma ray spectroscopy, multifrequency dielectric dispersion, and nuclear magnetic resonance (NMR). The advanced elemental gamma ray spectroscopy has been key for the creation of a robust mineralogical model, and to derive the matrix properties used to obtain an accurate porosity free of matrix and gas effects with the combination of NMR porosity. The dielectric dispersion provides a direct estimation of water volume, which, in turn, helps to adjust the conventional method of water saturation from resistivity. The good correlation between the petrophysical properties estimated from the proposed workflow and the core analysis, demonstrates the benefits of using the advanced log measurements. The final step of the workflow consists in the definition of poro-fluid facies determined with a new methodology, called NMR factor analysis, that is based on the extraction of multimodal information from the NMR T2 distribution to determine the optimal number of dominant modes (factors) that allow describing the reservoir. Production logging results showed a good relationship between the poro-fluid facies and reservoir productivity.

No abstract

Lindero Atravesado field is located in Neuquen, western Argentina. It has been under development since 2012. Originally, its development was focused on conventional formations (Quintuco, Sierras Blancas and Lotena), considering the Punta Rosada and Lajas formations as geological traps. Development is now focused on these traps, especially in the northwest region the field, called the Lindero Atravesado Occidental. Fundamental challenges in the Occidental region of the field include optimum fluid engineering, avoiding shear-sensitive fluid systems, high PAD percentage and safe operational efficiency in deep HPHT wells. However, original frac designs were optimized through a traditional cycle of design and pressure-matching evaluations using a conventional frac simulator. Obtained fracture geometries were bounded in length and a considerable height growth was observed. Other studies used microseismic, sonic profiles or traceable sands, and showed fractures contained in height and longer fracture lengths than those obtained with the traditional adjusted model. A fracturing model coupled with microseismic interpretation allowed a better characterization of fracture geometry, vertical covering, effective production fracture length and drainage area efficiency, based on numerical production simulations and matching. The last point will have a direct impact on well spacing and future selection of in-fill locations. This paper will discuss a fully integrated approach for field planning optimization, starting with geosciences characterization, workover, stimulation and production history matching, with a direct impact on well gridding and estimated ultimate recovery (EUR) per well.

No abstract