Fracture characterization in Upper Permian carbonates in Spitsbergen: A workflow from digital outcrop to geo-model

Kristine Larssen,Kim Senger,Sten-Andreas Grundvåg

doi:10.1016/j.marpetgeo.2020.104703

Kristine Larssen, Kim Senger + Show 1 more

Open Access

https://doi.org/10.1016/j.marpetgeo.2020.104703

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Abstract

Carbonates represent major hydrocarbon reservoirs, but often exhibit highly heterogeneous reservoir properties. Outcrop analogues provide important insights into how parameters such as porosity, permeability and natural fractures vary. As such, outcrops can bridge the scale gap between spatially extensive but poor-resolution seismic data and 1D high-resolution well data. However, traditional geological fieldwork typically gathers insufficient data to construct robust geological models. In this study, we have specifically set out to gather key data sets that enable the construction of a geology-driven model. We illustrate this workflow using the exceptionally well-exposed carbonate-dominated outcrops of the Kapp Starostin Formation in central Spitsbergen, Arctic Norway. We fully utilize emerging technologies, notably geo-referenced digital outcrop models (DOMs), to be able to gather quantitative sedimentological-structural data from otherwise inaccessible cliffs. DOMs generated from digital photos are used directly for automatic and manual mapping of fractures. The digital data are complemented with traditional fieldwork (sedimentological logging, scanlines, structural characterization) in order to strengthen the dataset. The geo-modelling involves traditional facies and petrophysical modelling of the 12 identified facies, along with outcrop-based discrete fracture modelling. Finally, the static geo-model is upscaled, and its applications are discussed. The presented workflow uses carbonate outcrops of the Kapp Starostin Formation as input but is highly applicable for other studies where outcrops can be utilized as direct input to constrain a geological model.

Highlights

Carbonate reservoirs represent important hydrocarbon reservoirs (Kingston et al, 1983; Roehl and Choquette, 2012), major groundwater aquifers (Lattman and Parizek, 1964), geothermal reservoirs (Montanari et al, 2017) and potential CO2 sequestration sites (Shakiba et al, 2016)
In addition to variations of fracture aperture, their emphasis lay on variations connected to thickness of fracture units, the fracture shape and dispersion level on fracture orientations. These results suggest that changing the dispersion level of orientations, the fracture shape or fracture unit thicknesses have minor to none influence on the fracture porosity used in their base case
This study focuses on the integration of traditional and digital outcrop data into a geological model, with the emphasis on character izing the natural fracture network in the Kapp Starostin Formation

Summary

Introduction

Carbonate reservoirs represent important hydrocarbon reservoirs (Kingston et al, 1983; Roehl and Choquette, 2012), major groundwater aquifers (Lattman and Parizek, 1964), geothermal reservoirs (Montanari et al, 2017) and potential CO2 sequestration sites (Shakiba et al, 2016). In contrast to most siliciclastic reservoirs, carbonates often exhibit het erogeneous reservoir properties. Pore systems in carbonate systems are often complex and span from the micro-scale (e.g. pores and frac tures) to km-scale cave systems (Ahr, 2011; Loucks, 1999; Lønøy, 2006). In particular, are important elements that contribute to improved reservoir properties and flow in many carbonate reservoirs (e.g., Ding et al, 2012; Reijers and Bartok, 1985). Fracture systems can be investigated across numerous scales, including seismic (Liu and Martinez, 2014; Perez et al, 1999), dynamic field data (Ozkaya and Richard, 2006), outcrop analogues (Agosta et al, 2010; Guerriero et al, 2013), well data (Khoshbakht et al, 2012; Xu and Payne, 2009) and laboratory tests (Jones, 1975)

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