HOME

Archive » Abstracts » Search	*2004/ 2005 SEASON* **STAVANGER JANUARY MEETING Venue: Rica Forum Hotel, Stavanger Date: Wednesday, 5th January, 2004 Time: 11:00 a.m. Lunch will be provided at 12:00 Multiple Uses of Borehole Images in Sandstone Reservoirs, Sirt Basin by Birger Hansen, Eriksfiord AS (presenter), and Thomas Weihe, Wintershall Libya Abstract Borehole images from 20 wells from the Sarir reservoir in Libyan concession 97 have been investigated. Image observations were combined with description of all available core material, and compared with seismic, stimulation and simulation data. The facies spectrum of the reservoir section can be best described as deposits of a terminal fan system interacting with a lacustrine lake environment. The sandstones have been deposited in an ephemeral fluvial environment with channels, sheet floods and interchannel sandflats. The sedimentary succession is locally interrupted by igneous intrusions and capped by effusives. The structures in concession 97 are the result of a complex interaction of normal faulting and strike slip faulting, modified by ascent of magma and escape of hydrothermal fluids. The fractures and deformation structures seen on images thus show a great variety, but coupling with the sequence stratigraphy, it was possible to make a unified tectono-stratigraphic model. Today, the reservoir is under a stress regime determined by the Hellenic arc system. The maximum horizontal stress is about the same as the vertical stress. N trending faults are active in this stress regime if pore pressure is increased, and shale will become unstable on horizontal wells drilled across the compressed WNW rift derived faults. About the author:** Birger’s academic career focused on the role of fluids in high pressure metamorphic rocks. Since 1981 he has worked on subsurface geology and geomechanics. He founded Z&S Geologi AS (1985-1998), Eriksfiord AS (2001) and Eriksfiord Aps (2004). These companies provide(d) geoscience services for oil companies, mostly based on borehole image logs.

Abstract

Borehole images from 20 wells from the Sarir reservoir in Libyan concession 97 have been investigated. Image observations were combined with description of all available core material, and compared with seismic, stimulation and simulation data.

The facies spectrum of the reservoir section can be best described as deposits of a terminal fan system interacting with a lacustrine lake environment. The sandstones have been deposited in an ephemeral fluvial environment with channels, sheet floods and interchannel sandflats. The sedimentary succession is locally interrupted by igneous intrusions and capped by effusives.

The structures in concession 97 are the result of a complex interaction of normal faulting and strike slip faulting, modified by ascent of magma and escape of hydrothermal fluids. The fractures and deformation structures seen on images thus show a great variety, but coupling with the sequence stratigraphy, it was possible to make a unified tectono-stratigraphic model.

Today, the reservoir is under a stress regime determined by the Hellenic arc system. The maximum horizontal stress is about the same as the vertical stress. N trending faults are active in this stress regime if pore pressure is increased, and shale will become unstable on horizontal wells drilled across the compressed WNW rift derived faults.

About the author:

Birger’s academic career focused on the role of fluids in high pressure metamorphic rocks. Since 1981 he has worked on subsurface geology and geomechanics. He founded Z&S Geologi AS (1985-1998), Eriksfiord AS (2001) and Eriksfiord Aps (2004). These companies provide(d) geoscience services for oil companies, mostly based on borehole image logs.