Among possible characterization techniques used in horizontal wells, geophysical surveys seem to be very promising in giving a set of images of the reservoir and the surrounding layers at different scales. This paper demonstrates the usefulness of horizontal well geophysical surveys in different frequency bandwidths for reservoir studies. The paper shows several field examples. In the low frequency bandwidth, VSPs give a coarse image of the reservoir and of the layers situated below, with a vertical resolution of several 10's of m (first example). Full waveform acoustic data produce near-borehole structure images up to a distance of 15 m from the borehole with a vertical resolution of several 10's of cm (second example).
The paper points out the necessity of having very high resolution seismics (intermediate between VSP data and acoustic data) to obtain structural images up to a distance of 100 m from the borehole. An example shows the results obtained in the 1-to-5 kHz bandwidth on a test site. The field records show reflected arrivals from boundaries up to a distance of 50 m from the horizontal borehole.