Abstract
Reservoir management optimization requires a detailed description of the geometry and the properties of the reservoir. For horizontal wells, knowing accurately the position of the borehole in the reservoir is critical. However, seismic techniques do not have sufficient resolution to provide the position of the well with respect to the reservoir boundaries with desired accuracy. Sonic measurement on the other hand has the potential to provide such information. We conducted experiments in horizontal wells in Oman using a commercial multi-receiver sonic tool modified for imaging, with extended spacing between the transmitter and the receivers. Although the tool characteristics are not optimized for the imaging, we obtained interesting results when the reflectors have sufficient strength, thus showing the potential of this technique. The pre-processed and migrated sonic images provided useful information on the geometry of the reservoir, which could be compared with seismic interpretation and field knowledge. Furthermore, we developed a specific processing technique that uses the four different waveforms acquired around the tool at each receiver station to separate the reflections coming from above the well and the ones coming from below. In this way, we could obtain images that could be interpreted more easily. In some instances, the position of the reservoir boundaries could be determined with an accuracy of 1 m up to a maximum distance of 10 m.
