GeoResources - Industry Sponsorship, Sobrarbe Reservoir (SobraRes) Project: Ainsa Basin, Pyrenees Foreland Basin

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Sobrarbe Reservoir (SobraRes) Project – Ainsa Basin, Pyrenees Foreland Basin

Proposal for Industry Sponsorship

  
         
 
 
         
         
 
Full version of the SobraRes Proposal is available for download (Acrobat 9 and higher, 7.3 MB)


Introduction

Lateral and vertical heterogeneities in facies, petrophysical properties and diagenetic overprint are critical parameters of targeted reservoirs. High-frequency, meter-scale vertical stacking patterns and their lateral variabilities within and across specific depositional environments exert a highly important control on fluid-flow behaviour in the subsurface. High-resolution data sets of the reservoir architecture and the lateral/vertical distribution of key reservoir features allow improved reservoir models and therefore reduce exploration risk. In addition, such data sets are essential for forward numerical models of sedimentary systems and fluid-flow behaviour during subsequent basin development. However, industry subsurface data sets bear inherent limitations in both vertical and lateral resolution imposed by the interpolation between wells and within 2D and 3D seismic data sets.

Seismic-scale, continuous outcrops across entire sedimentary systems, e.g. from alluvial plain to basin in the case of deltas, are rare. In few field examples, vertical sediment stacking patterns are associated with limited lateral dimension, providing a tolerable 2D coverage of the system. In most cases, 2D coverage is limited to either coastline-parallel, oblique or progradation-parallel orientation. Aerial or satellite images may provide additional architectural information, however, rarely do they provide 3D information.

A total of 17 MSc theses have been conducted at the Institute of Earth Sciences. They include an exceptionally detailed database for the SobraRes Project. We propose to further develop this database for high-resolution reservoir analogue analysis in 2D and 3D, which will be very well suited for future sedimentary and fluid flow modeling.


Geological Framework and Database

The Eocene (Middle-Late Lutetian) Sobrarbe Delta System (SDS) developed at the southern margin of the Ainsa piggy-back basin, in the Pyrenees Foreland Basin (PFB), northeastern Spain. Towards the foreland basin axis, the SDS interfingers with the basinal succession of the San Vincente Formation. It comprises the Ainsa Turbidite Channel System (TCS), which ranks among the best studied outcrop examples of confined turbidite deposition. Development of the PFB and the SDS is closely related to the oblique collision of the Eurasian plate and the Iberian micro-plate. Pre-Middle to -Late Lutetian sediment input to the Ainsa basin was derived from the eastern Tremp basin, which started to develop and close earlier than the Ainsa Basin. At this time, the Ainsa basin was in an underfilled foredeep basin stage with predominantly axial transport (ESE-WNW). When significant compression extended further to the west, the Ainsa piggy-back basin developed. It was bounded by the frontal thrust of the Pyrenean orogen (N), the southern thrust ramp of the piggy-back basin (S, Sierras Marginales) and two lateral structural ramps (E, W; Mediano-, Boltana-Anticline). Previous axial sediment transport was finished and replaced by transversal sediment input from the outer basin margin, the SSE to NNW prograding SDS. Sediment input from the Pyrenean orogen was subordinate during the Middle-Late Lutetian and is located north of the interest area. The development of the SDS marks the change from the underfilled foredeep basin stage to the sediment-balanced and overfilled basin stage.

The Sobrarbe Delta System (SDS) in the Tertiary Pyrenees Foreland Basin (PFB) shows exceptional exposure, which is laterally and vertically continuous at seismic scale. Three outcrop transects of 12-25 km each run in the direction of long-term progradation and parallel to the paleo-coastline. Outcrop transects include:

2D transect from alluvial plain to basin – Length 20 km, thickness 70-300 m, dip section;
2D transect from alluvial plain to basin – Length 25 km, thickness 50-300 m, dip section
2D transect in delta plain to alluvial plain – Length 12 km, thickness 50-150 m; strike section
2D and 3D data in delta slope to basin – Area 30 km2, large seismic-scale exposure;

Outcrops are well accessible in the field for high-resolution measuring/sampling of vertical sections and physical/optical tracing of bounding surfaces. Adjacent hills allow oblique-angle pseudo-aerial views for geometric analysis. High-resolution mapping and optical tracing of sediment geometries and bounding surfaces can be performed by using satellite images (e.g. Quickbird, Ikonos).


Workflow and Technical Program

Outcrop data acquisition will further develop the existing data set by (i) increasing the spatial resolution of sediment geometries and their bounding surfaces; (ii) measurements of petrophysical parameters; (iii) adding high-resolution-data from satellite images; (iv) differential GPS referencing. Data types measured include:

Vertical stacking patterns
Spectral GR in outcrop
Physical sediment surfaces (time lines)
High-resolution satellite image analysis
Architectural analysis

Geophysical and reservoir properties measured include:

Modal analysis and diagenetic alteration
Pore structure
Poro-perm measurement


Objectives

Key objective is the improved understanding of heterogeneities in reservoir facies and petrophysical parameters in foreland basin delta systems by high-resolution outcrop analysis. Outcrop-based data sets and 2D/3D models will be compared to producing subsurface foreland basin delta systems from the sponsors´ E&P activities.

Sedimentological Map – GIS provides integrative and spatially accurate acquisition and integration of all surface geological data (bounding surfaces, sediment geometries). In combination with high-resolution DEM data and satellite images a 3D sedimentological map with focus on reservoir properties will be developed for the SDS.

2D/3D Reservoir-Outcrop Analogue Model – A 3D reservoir-outcrop analogue model of the SDS will be performed with standard industry software. Main features include: i) Visualization of bounding surfaces and sediment bodies, ii) Pseudo-well (vertical section) correlations, calibrated by physical bounding surfaces and sediment bodies; iii) Property modeling of porosity and permeability as well as other petrophysical parameters; iv) 3D reservoir model.


Status

This proposal is open for sponsorship by single or multiple companies.


Full version of the SobraRes Proposal is available for download (Acrobat 9 and higher, 7.3 MB)
  
       
 
 

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