Unconventional Natural Gas and Oil Institute

Colorado School of Mines

UNGI CIMMM International Unconventional Resource Consortium


The Vaca Muerta Formation in the Neuquen Basin, Argentina is a world class source rock. The integrated consortium offers projects to characterize the source rock potential of the basin, conventional and unconventional accumulations in terms of petrophysical, mechanical and fracture characteristics in order to provide custom drilling, completion and hydraulic fracturing models for the basin in optimizing the recovery by developing coupled geological, geomechanical and flow models

The objective of the UNGI VacaMuerta Consortium is to characterize the source rock potential of the Vaca Muerta formation in the Neuquen Basin in Argentina. The consortium is established as a multidisciplinary project bundle to characterize the hydrocarbon accumulations from fracture systems, porosity, permeability and in situ stress state perspective and use the knowledge to optimize drilling, completion and hydraulic fracturing operations in the basin by developing coupled geological, geomechanical and reservoir flow simulation model. The Vaca Muerta Formation is the world class source rock. The total organic carbon content of the Vaca Muerta ranges from 2 - 6 wt.% and the type of kerogen is Type I and II (sapropelic - oil prone). The shale interval ranges in thickness from 300 to 1300 ft. A part of the shale interval is present in the oil window and in deeper parts of the basin the shale is in the gas window. The production in the Neuquen Basin has been ongoing for over 100 years and is currently being explored for the unconventional resources in the basin. The initial projects include geological and geomechanical characterization of the reservoir and seal formation.

Stratigraphic Characterization of Vaca Muerta Reservoir: The stratigraphy and reservoir characterization components of the consortium include compilation of a subsurface database, and an initial assessment of Vaca Muerta petroleum system from current literature. This is followed by documentation of regional outcrop stratigraphy, integration with regional and 3-D seismic data to allow construction of a sequence stratigraphic framework for the Neuquen basin. Outcrops of the Vaca Muerta system the Neuquen Basin is being integrated with subsurface data in the basin. Reservoir characterization of key reservoir intervals using cores and outcrops is accomplished within this stratigraphic framework. The project plans to use high-resolution SEM analysis (QEMSCAN®) of samples from outcrop and core, combined with standard petrographic techniques and inorganic geochemical analyses of samples, to characterize Vaca Muerta mineralogy and diagenesis, to help quantify the Vaca Muerta pore systems, and to integrate that data with larger-scale flow unit compartments and connectors. The results of these efforts will allow the principal investigators Dr. Sonnenberg and Dr. Humpherey to document and map the lateral and vertical heterogeneity of reservoirs in outcrop and at the inter-well scale.

Fracture mapping, analysis and Sub-regional Tectonic and Structural Analysis: This project includes analysis of outcrop and core description to document both open and closed fracture systems, and to construct a 3-D model of this sub-regional system. In conjunction with the fracture characterization study, the in situ stress and pore pressure is determined and a 3D in situ stress and geomechanical model is being developed based on the integrated study findings. The current world stress map lacks data in the Neuquen basin. Therefore, we will develop a better understanding integrating the fracture characterization, geological history, drilling and production data in the region, seismic and well log analysis to provide an updated Neuquen stress map which is essential for field development and production analysis in the region and potential reserve uncertainty analysis and risk analysis for the investments in the area. The project is co-led by Dr. Steve Sonnenberg, Dr. Azra Tutuncu and Dr. John Humpherey.

Coupled Mechanical and Acoustic Properties and Permeability Core Measurements: The UNGI Geomechanics laboratory has been established at the Petroleum Engineering Department by Dr. Azra Tutuncu and a custom designed MTS load frame equipped with elastomer technology enables us to conduct low seismic frequency (up to 200 Hz) and ultrasonic frequencies (100 KHz, 150 KHz and 1 MHz) anisotropic velocity measurements along with triaxial deformation tests to simultaneously at in situ stress and elevated pore pressure and temperature conditions. The core measurements using the new geomechanics system provides realistic coupled acoustic, mechanical, permeability and strength characteristics of the Vaca Muerta reservoirs and its seal formations. Nano-scale SEM, AFM, CT-Scan, NMR and XRD measurements are integrated into large scale understanding and a grain contact adhesion hysteresis with the frictional sliding component is coupled with reservoir flow simulator to explain the hysteretic deformation behavior and the time-dependent alterations observed from the experiments in micro-scale for rock-fluid interactions that will benefit wellbore stability, drilling and hydraulic fracturing design and analysis. Laboratory-measured quantities will be compared to the log derived moduli and attenuation measurements for investigating the deformation and dispersion characteristics of the reservoir formations and their seals and key controlling factors impacting the production in Vaca Muerta.

Coupled Geomechanics Model and Wellbore Stability: This part of the project is also led by Dr. Azra Tutuncu in determining local variations in the in situ stress, pore pressure, deformation characteristics and obtaining stress dependence of mechanical, acoustic properties, porosity and permeability by conducting coupled laboratory core measurements under true in situ stress and elevated pore pressure that will contribute better understanding of the reservoir characteristics, static and dynamic moduli differences and their stress dependence that are critical input for building an accurate fully integrated geomechanics model, wellbore stability and wellpath optimization, hydraulic fracture design and execution and production portfolio management. The deliverables also include coupling the fracture network analysis into the geomechanics findings to conduct wellbore stability and wellpath optimization analysis using offset drilling well data, well logs and seismic data in addition to representative core and cutting measurements to calibrate the in situ stress state in the Vaca Muerta formation to provide recommendations for optimized drilling, completion and critical input for fracture design.

Drilling and Completion Best Practices: Drilling and completion best practices for unconventional resource acquisition in Vaca Muerta Petroleum System will be delivered. The team is currently many differing technologies and techniques used today in the drilling and completion of various world-wide analog geologic systems and defining the potential drilling and completion impediments to implementation of the various technologies and techniques identified as useful in the Vaca Muerta. We are determining the efficiency of resource recovery, economics, safety, and environmental impact for these various technologies and techniques. The deliverable of this first step would be a set of recommended practices to implement. Upon field operations and implementation, the team would analyze field results and determine efficiencies as they occur. The team would also identify those problems that need resolution for future consortium activity. Dr. Azra Tutuncu has been leading this part of the project.

Hydraulic Fracture Stimulation Model: The objective of this part of the project is to develop a hydraulic fracture stimulation model(s) for the zone(s) targeted during the reservoir characterization as the sweet spots in the formation. The focus of this component is the optimum placement and design of the treatments and will be initiated once the geological and geomechanical model is in built. Required fracture conductivity and fluid selection for the zones of interest will be evaluated. Additionally, the optimum spacing of the treatments will be evaluated. These spacing requirements will be closely integrated with the drilling technology component of this proposal, along with completion technologies (i.e. plug-n-perf methods versus packer/ball systems). Fracture conductivity, which is critical to long-term production, will be integrated with the geo mechanical and stratigraphic models. The project is led by Dr. Azra Tutuncu.

If you are interested in becoming a member of the UNGI Vaca Muerta Consortium and collaborating with leaders of the Unconventional Research at Colorado School of Mines, please contact Dr. Azra N. Tutuncu for further information and how to become a member.

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