High-resolution acoustic imaging from a borehole to detect a nearby well

Abstract

A new imaging application is presented using sonic waveform data for ranging to locate a nearby borehole. The challenge of locating a nearby well from a borehole is commonly addressed with electromagnetic (EM) or passive magnetic ranging methods, which can suffer from poor resolution and penetration and require the presence of a conductive or magnetic casing. In addition, the deeper reading active EM methods do not work well when the two boreholes are orthogonal. In contrast, acoustic imaging requires only an impedance contrast between the target object and the surrounding formation, which is adequately provided by the presence of a fluid-filled borehole, even without casing. Here we use acoustic full-waveform sonic data to identify the location, distance, and direction to a target vertical borehole from a nearby highly deviated observation well. The target borehole was located at a distance of about 9 ft with an accuracy of less than 0.5 ft, which was subsequently confirmed by drilling. In addition, acoustic waveform data made it possible to image up to 100 ft above and below the observation well at a resolution comparable to gamma ray and electric logs from the target well.