Schlumberger Technology Corporation

Thomas L Marzetta

Weng C Chew

Christopher V Kimball

A method and apparatus investigating a circumferential segment of a borehole with an array of elements, which in effect spatially samples the segment, is described whereby, with a single circumferentially oriented array of spaced-apart elements sufficient overlap can be synthesized so as to reduce artifacts attributable to the spatial sampling. Measurements derived from circumferentially successive elements are combined, such as by summing to establish a desired overlap. In the described embodiment to a single lateral array of small electrodes is used to inject survey currents into the borehole wall and each current is measured. Measurements derived from pairs of successive survey currents are then summed to provide the desired overlap.

Method and apparatus for investigating a borehole using an array of

Disclosed is sonic well logging which gives good results both in open and in cased boreholes. New use is made of the energy content output from a multireceiver tool to find a coherence measure for the received sonic energy and to find the peaks of that coherence measure at each depth level so as to produce a number of new logs of parameters of those peaks. Examples are a slowness/time coherence log for those peaks, as well as new logs related to the arrival times of the coherent energy associated with the peaks and the energy attenuation for those arrival times.

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Danbury, CT, United States of America

Thomas L Marzetta