Processing array acoustic-logging data to image near-borehole geologic structures

Abstract

Imaging near-borehole structures using acoustic-logging data depends on the data-processing method used. We demonstrate that extracting the up- and downgoing reflections from the data and using those separately for the imaging can significantly improve the image quality. A parametric wave separation is first applied to array data to separate direct and reflection waves. In particular, we use a transmitter array gathered from successive source positions to extract the upgoing reflection. Reflection data can also be enhanced by stacking data along the reflection moveout in array using approximate structural dip information. Implementation of this method to acoustic-logging data processing improves imaging quality, making it possible to image near-borehole geologic structures using conventional array acoustic-logging. A potentially important application of drilling steering is using logging-while-drilling acoustic measurements.

A method to determine the strike of interface outside of borehole by monopole borehole acoustic reflections

“…Recent studies of this socalled borehole acoustic reflection logging have shown that it can detect about 10-20 m away from borehole. In addition, we can use such a method in acoustic logging-while-drilling (ALWD) operations for geo-steering (Tang et al, 2007).…”

“…However, the details of data processing methods and software are still not clear to the industry. Baker Hughes developed dipole shear measurements to infer the strike information of the structures far from the borehole (Tang et al, 2007;Wei and Tang, 2012). Bohai Drilling of CNPC developed an acoustic reflection logging tool and the data processing software in 2007, which are similar to BARS (Li et al, 2014).…”

Experimental study of the azimuthal performance of 3D acoustic transmitter stations

“…The acoustic waves reflected by the near-borehole interfaces with non-continuous acoustic impedance are obtained through acoustic reflection logging (Hornby 1989;Ellis et al 1996;Esmersoy et al 1997Esmersoy et al , 1998Chang et al 1998;Yamamoto et al 1998;1999). Migration imaging techniques that are similar to those used in seismic exploration are then employed to visualize small-scale geologic structures from a few meters to dozens of meters away from boreholes (Yamamoto et al 2000;Tang 2004;Pistre et al 2005;Li et al 2008;Chai et al 2009;Tang et al 2007). Acoustic reflection logging generally facilitates more in-depth investigation than conventional acoustic logging, and it also yields images with higher resolution than those obtained through seismic exploration.…”

“…In dipole remote acoustic reflection imaging, dipole acoustic sources are used to image small-scale, near-borehole geologic structures (Tang 2004;Patterson et al 2008;Tang et al 2007;Tang and Patterson 2009;Tang and Wei 2012a, b;Wei et al 2013). Although low-frequency dipole acoustic sources provide for more thorough radial investigations, the directivities of the sources and the receivers limit the azimuthal resolution with 180°azimuthal ambiguity.…”

Deep Shear Wave Imaging Using Cross-dipole Wireline Data

“…Although many papers have already been written about the subject (E.g., Tang et al, 2007, Tang andPatterson, 2009), this paper mainly serves to give a clear and concise overview about the underlying measurement principles, theory, and processing methodology and to create awareness among nonborehole acoustic experts. To underline the successes that already have been achieved with this technology two case studies will be presented at the workshop.…”