High resolution borehole-to-borehole seismic tomography can provide much of the information needed to identify subtle oil reservoir heterogeneities. To date, much of the high resolution cross-well research has involved the use of fluid-coupled piezoelectric seismic sources. However, in practical commercial applications of fluid-coupled sources, some consideration must be given to deploying the source in a manner that overcomes the inherent problems associated with a fluid-coupled design. One major problem is that a significant portion of the energy goes into the generation of borehole tubewaves. This energy loss results in a reduced efficiency of the source. In general, tubewaves are a significant problem in applications involving either borehole sources or receivers. Often, tubewaves can be so prolific in borehole environments that support their generation and propagation that they can significantly mask the seismic signals of interest. The capability to suppress borehole tubewaves and/or constructively control this fluid energy could significantly enhance the signal-to-noise ratios attainable in a variety of borehole seismic applications. The objective of this project is to design a borehole tubewave damper probe that is an effective application of proven surge suppression techniques employed in oil field applications for many years. This design is believed to be unique and is expected to reduce tubewave amplitudes by at least 20 dB. The project involves the construction of two tubewave damper probes based upon this design, Computer modeling and field investigations of these devices will be directed toward assessing the probes' capabilities for tubewave suppression and control. The Phase I work allows for minor design modifications of the probes and subsequent testing.Anticipated Results/Potential Commercial Applications as described by the awardee:Borehole tubewaves can present a problem in any seismic application that uses boreholes (e.g., vertical seismic profiling (VSP), inverse-VSP, and cross-well applications). The Phase I effort will provide important theoretical and practical information about suppression (in receiver boreholes) and control (in source boreholes) of tubewaves. This work addresses the feasibility of using the damper probe design for both applications. In the future, borehole seismics will involve processing developments in the areas of reflection tomography with application to both cross-well and single borehole seismics. In these applications, tubewaves are a major source of noise and ultimately limit the dynamic range capability of any borehole receiver system. Hardware control of these interfering signals could play a significant role in the evolution of reflection seismics from research to practical commercial application.
