E. Ted Bornemann1
(1) Schlumberger, Sugar Land, TX
Abstract: Stress and Structure from Logging-While-Drilling Images
Borehole images recorded while-drilling provide quantitative geological information for structural analysis in three domains.
Images allow the recognition and orientation of bedding dips, faults and fractures. The derivation of structural dip and its projection away from the wellbore including fault and fold analysis is part of a standard structural analysis. These images are of particular importance in areas of steeply dipping strata or in areas where seismic imaging cannot deliver the needed resolution.
Far-field stress analysis is greatly aided by the analysis of drilling induced wellbore features. The position and morphology of breakouts, high echelon shear fractures and tensional fractures on the borehole wall is determined by the directions and magnitudes of the three principal stresses. Induced wellbore features are extremely well imaged by LWD-resistivity images and their analysis aids in the establishment of a current geo-mechanical model used for well panning and borehole stability issues.
Density or resistivity images, particularly when delivered in real-time, are a powerful tool for geo-steering a horizontal well, which typically is drilled parallel to a formation boundary or fluid contact. A well plan, based on seismic and offset wells, often misses small changes in formation dip which may lead to lost net pay. Real-time images help to understand the geology and make the proper geosteering decisions.
Examples of the above outlined applications will be presented and the relative advantages and limits of resistivity and density images will be discussed.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana