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Application of horizontal stress directions interpreted from borehole breakouts recorded by four-arm dipmeter tools

Authors
Identifiers
DOI: 10.1016/b978-0-444-88943-0.50045-9
Disciplines
  • Earth Science

Abstract

The Barents Sea has a tectonic history that makes the search for hydrocarbon-filled traps challenging. Dry wells have been drilled on several promising structures. Analysis of data from several of the dry wells show that the structures have earlier been filled with gas/oil. The leaks appear to have occurred through the fault planes that bound these traps. The borehole breakouts in wells are often recorded by four-arm dipmeter tools. The recorded variation in the hole shape in the various rock layers can be organized and interpreted and the subsurface, horizontal stress directions may be determined. In general, faults that are oriented 90° to the least horizontal stress direction, are most likely to fail in sealing trapped hydrocarbons. This paper shows principally how one may grade the probability for success on exploration prospects based on the post migration, principal horizontal stress directions, and the orientations of the bounding fault(s). Caliper data from three wells A, B and C, in the “Gas Field X” area, on the western hemisphere, have been interpreted. Well A has an average borehole breakout azimuth of 45° in strata deposited post the hydrocarbon migration. This corresponds to a maximum horizontal stress azimuth of 135°. Gas chimneys above two faults with the most unfavourable orientations support the model that the sealing capacity of fault planes is influenced by anisotropic horizontal stress acting post migration. In areas where four-arm caliper data are available, interpretations of anisotropic stress may be used to evaluate and to set priority on exploration prospects.

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