Integrating Pilot Well Measurements for Horizontal Well Planning - a Case Study, Vaca Muerta Formation, Neuquén Basin, Argentina

Abstract

The Jurassic- and Cretaceous-age Vaca Muerta formation of the Neuquén Basin, Argentina, is a heterogeneous self-sourcing reservoir that is complicated by tectonic and volcanic influences. As an unconventional reservoir, its characterization requires the evaluation of key properties related to the production drivers: reservoir quality (RQ), drilling quality (DQ), and completion quality (CQ). A methodology is presented to maximize horizontal well success by identifying optimum horizontal well landing locations through integration of multidimensional petrophysical and geomechanical properties. This ongoing case study identifies of the key properties for RQ, DQ, and CQ through correlation analysis and production validation. The methodology uses a systematic and quantitative probability calculation to determine the lateral landing score (LLS) for all depths along a vertical pilot wellbore. Core-calibrated petrophysical evaluations of the interbedded siliciclastics, organic shales, ash beds, and tight limestones of the Vaca Muerta quantify uncertainty in estimates of reservoir properties (e.g., mineralogy, maturity, porosity, fluid saturations, and permeability) and RQ. Stress profiles, calibrated using core evaluation and stress tests, provide a predictive model of geomechanical properties (e.g., anisotropic elastic properties, in-situ stresses, wellbore stability, and rock fluid sensitivity). These parameters are critical for DQ and CQ predictions. Production results define appropriate normalization and weighting of properties for the LLS probability. Tectonic stresses in the Vaca Muerta may promote horizontal fractures that create restrictions to fracture growth and/or induce pinch points. Previous approaches to determine the target location in an unconventional resource play using geomechanical inputs alone may not apply to the Vaca Muerta because they overlook the effects of the fracture complexity induced by the stress regime of the prograding depositional environment. A high LLS occurs where positive RQ, DQ, and CQ values exist in sections thick enough to drill. The LLS brings together measurements from multiple domains to provide a qualitative, comparative, and repeatable ranking of ideal landing locations in tectonically active unconventional plays. Implementing the LLS as a decision-making tool for horizontal well placement generates both an optimized landing point and completion design. The workflow is iterated with available horizontal well production data to validate the relevant production drivers.