Abstract

Analysing borehole breakouts is a well known method for obtaining horizontal stress directions. In this study dipmeter data from 46 wellbores in the Tampen area in the northern North Sea were analyzed for breakouts. The analysis identified a large problem of differentiating borehole breakouts from key- seats. Even at very low bole deviation elongations seemed to align with hole azimuth. This hampered breakout identification, and indicated that key seating possibly is a much larger problem than implied in earlier breakout work from the North Sea From our findings and also based on other stress data from the area it seems as though the wellbore very often deviates in the direction of the least horizontal stress, thereby masking breakouts as key seats. To examine this observation the effect of bedding and stress on the wellpath were examined, without yielding a solution to the problem. For future stress analyses in the northern North Sea enhanced use of imaging data will be important to avoid similar problems. Borehole breakouts identified by dipmeter analysis primarily seem to give an indication of the in-situ stress direction, as long as the number of observations are statistical significant. Traditional breakout analysis should not be trusted alone, but always be constrained by, for instance, image analysis.

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