--> Abstract: High-Resolution Imaging of a Karstified Carbonate Reservoir Analog, Late Carboniferous, Spitsbergen, by Walter H. Wheeler, David Hunt, Jan Steinar Ronning, Einar Dalsegg, and Alvar Braathen; #90039 (2005)

Datapages, Inc.Print this page

High-Resolution Imaging of a Karstified Carbonate Reservoir Analog, Late Carboniferous, Spitsbergen

Walter H. Wheeler1, David Hunt2, Jan Steinar Rønning3, Einar Dalsegg3, and Alvar Braathen4
1 Center for Integrated Petroleum Research, University of Bergen, N-5007 Bergen, Norway
2 Norsk Hydro Research Centre, Bergen, Norway
3 Geological Survey of Norway, N-7491 Trondheim, Norway
4 Center for Integrated Petroleum Research, Unifob, University of Bergen, N-5007 Bergen, Norway

Karstified platform carbonates are major exploration targets, yet their complex reservoir architecture poses significant exploration and production challenges. We present 3D reservoir-analog images combining outcrop studies and high-resolution geophysical images of the geobody interior. Foci include the geometry, frequency and interconnectivity of breccia bodies, dolines and faults at reservoir and seismic scales, as well as the relation between karst formation and deformation. The study area is a kilometre-wide mesa with cliff-side exposures of karst breccias, faults, and flexures in Late Carboniferous platform carbonates. The geophysical imaging consists of ground-penetrating radar (GPR) profiles, reaching 50 meters into the outcrop, and electrical-resistivity tomography (ERT) profiles, modelled to 120 m depth. Hence the GPR, ERT and outcrop ground-truth constrain the karst geometry at scales relevant to both reservoir evaluation and seismic interpretation. For example, a cliff-side exposure shows a 100m-wide, “V”-shaped, flexural collapse structure in cross section. Closely-spaced (12m) GPR profiles adjacent to this cliff exposure show the “V” to be one of a family of adjacent, doline-like circular depressions. The “V” and adjacent depressions lie towards the upper side of a monocline (500m-wavelength). The toe of this monocline is characterised by local axis-parallel faulting (imaged using GPR) coincident with a steep, deep low-resistivity zone (imaged using ERT) suggesting karst. Elsewhere, a cliff face along a flat part of the mesa exposes a field of breccia pipes. Here, coincident GPR and ERT profiles show lower strata locally disrupted by chaotic reflections (GPR image), and a vertical, pipe-like resistivity structure (ERT image).

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005