3D borehole imager

摘要

Logging tools and methods for obtaining a three-dimensional (3D) image of the region around a borehole. In at least some embodiments, a 3D imaging tool rotates, transmitting pulses that are approximately a nanosecond long and measuring the time it takes to receive reflections of these pulses. Multiple receivers are employed to provide accurate triangulation of the reflectors. In some cases, multiple transmitters are employed to obtain compensated measurements, i.e., measurements that compensate for variations in the receiver electronics. Because reflections occur at boundaries between materials having different dielectric constants, the 3D imaging tool can map out such boundaries in the neighborhood of the borehole. Such boundaries can include: the borehole wall itself, boundaries between different formation materials, faults or other discontinuities in a formation, and boundaries between fluids in a formation. Depending on various factors, the size of the borehole neighborhood mapped out can be as large as 1 meter.

主权项

1. A borehole logging method that comprises:
conveying an imaging tool along a borehole and tracking a position of the tool; transmitting an electromagnetic pulse having a width less than 2×10−9 seconds from the imaging tool in each of multiple azimuthal directions; receiving signals at spaced receivers of the imaging tool in response to each electromagnetic pulse, said signals corresponding to electromagnetic pulse reflections from one or more formation boundaries; processing each received signal to determine travel times from said electromagnetic pulse reflections; and forming a three-dimensional (3D) image of a formation region surrounding the borehole based at least in part on said travel times as a function of position and azimuthal direction.