Abstract Ultrasonic logging has been used extensively in Colombia, in the Andesfoothills, to quantitatively evaluate casing wear and deformation. Casingstrings can be lost to casing buckling, shearing and excessive wear. Activestresses applied to the casing strings from the active movement of faultscontribute to the degradation of casing integrity and strength. These deformations are very costly and often cause the well bore to beabandoned or re-drilled. Imaging of the casing in planar view, 2D cross-sectionand in 3D perspective view are often helpful to better understand thedeformation extent, location, and possible causes. A number of somewhat extreme examples of casing deformation due to activestress regimes are analyzed to demonstrate the circumstances that differentsize casings may be subjected to in areas of high lateral stresses. Some ofthese examples illustrate casing that appears damaged beyond repair, but isstill holding pressure and allows entry into the well. Other casing deformationis much less extreme, but reduces the casing strength very substantially. Casing internal diameters, thicknesses, and the acoustic impedance of thematerial behind the casing are measured and interpreted. These measurements arethen visualized using 1D, 2D, and 3D displays of the data. Correlations togeologic and geophysical events are shown in 3D to illustrate and definepotential high-stress, problem areas and help in casing design for the severeenvironment.