Borehole Breakout. Bibliographic Synthesis

Natural borehole breakout (borehole cross-section elongation) due to the fracturing and spalling of well walls has been used in recent years to determine the direction of stress in the Earth's crust. Its performances and scope of application are compared to those of other methods used in boreholes. An initial selection of information obtained by different logging tools appeared necessary to prevent any contamination of measurements by phenomena independent of deformation under stress. The principal parameters governing the amplitude and frequency of the phenomenon are reviewed. The outlook for the future of the method are examined, including the recent development of research on borehole breakout by the plastic deformation of the surrounding formations

Borehole Breakout. Bibliographic Synthesis L'ovalisation des trous de forages. Synthèse bibliographique

Natural borehole breakout (borehole cross-section elongation) due to the fracturing and spalling of well walls has been used in recent years to determine the direction of stress in the Earth's crust. Its performances and scope of application are compared to those of other methods used in boreholes. An initial selection of information obtained by different logging tools appeared necessary to prevent any contamination of measurements by phenomena independent of deformation under stress. The principal parameters governing the amplitude and frequency of the phenomenon are reviewed. The outlook for the future of the method are examined, including the recent development of research on borehole breakout by the plastic deformation of the surrounding formations. L'ovalisation naturelle des trous de forages par fracturation et écaillage des parois du puits est utilisée, depuis quelques années, pour déterminer la direction des contraintes dans la croûte. Ses performances et son champ d'application sont comparés à ceux des autres méthodes utilisées dans les forages. Une sélection initiale de l'information fournie par les différents outils diagraphiques apparaît nécessaire, pour éviter toutes contaminations des mesures par des phénomènes indépendants de la déformation sous contraintes. Les principaux paramètres contrôlant l'ampleur et la fréquence du phénomène sont passés en revue. Enfin, les perspectives concernant l'avenir de la méthode, et parmi celles-ci le développement récent de l'étude de l'ovalisation par la déformation plastique de l'encaissant, sont examinées