Reflection Sonic Imaging Using Slim-Hole Pipe Conveyed Sonic Tools

Modern slimhole pipe-conveyed sonic tools provide formation P- and S-wave slowness as well as high-end products such as cross-dipole anisotropy determination and geomechanics parameters. Reflection sonic imaging is another area of strong client interest; however, to date, the use of slimhole sonic tools for this application has been limited. One objective of this paper is to demonstrate that slimhole sonic tools can deliver results for reflection sonic (P- or S-wave) imaging as good as traditionally delivered by wireline openhole sonic tools. Beyond this objective is to demonstrate that the results can affect drilling or completion engineer’s decisions to, for example, target the next well interval or guide best locations for well fracking. In order to deliver data suitable for reflection imaging while retaining the data parameters to support the P- and S-wave slowness measurements for the well, the tool needs specific deployment considerations and is programmed to both extend the time recorded for the sonic waveforms as well as expanding the signal bandwidth of the recorded data beyond the default setting. Beyond that, the reflection imaging method and workflow are optimized for processing speed and delivery in time to make the targeted impact. For example, a fast-track processing can be delivered in a day that has 90% of the potential image quality, and a more complex result that is a 100% quality result is delivered some days later. Getting the recorded data to the person performing the imaging as rapidly as possible is one of the goals of this fast-track approach. If necessary, reflection imaging processing can be provided at the wellsite. Data from several unconventional and other wells are looked at. Integration with other borehole measurements, including borehole wall imaging and other logs, was a key part of the analysis, as well as integration with resistivity imaging when available. Both the fast-track and the expanded processing choices produce positive outcomes. Most interesting wells are extended-reach/horizontal wells where the location of near-wellbore reservoir boundaries of interest is not predictable from any borehole wall imaging results. In the horizontal well portion, this was particularly true for extremely lengthy sections. The accompanying figure shows an example fast-track image in an extended-reach/horizontal well. Here, the arrow points to the imaged reservoir boundary away from the well. In this example, the imaged reservoir boundary is seen from nearly 40 ft away from the well at the bottom of this section to around 10 ft at the top of the section.