An equivalent-tool theory for acoustic logging and applications

Abstract

The infl uence of an acoustic logging tool on borehole guided wave propagation should be considered in the processing and inversion of the guided waves for formation acoustic property estimation. This study introduces an equivalent-tool theory that models the tool response using an elastic rod with an effective modulus and applies the theory to multipole acoustic logging for both wireline and logging while drilling (LWD) conditions. The theory can be derived by matching the tool's acoustic impedance/conductance to that of the multipole acoustic wavefi eld around the tool, assuming that tool radius is small compared to wavelength. We have validated the effectiveness and accuracy of the theory using numerical modeling and its practicality using fi eld data. In fi eld data applications, one can calibrate the tool parameters by fi tting the theoretical dispersion curve to fi eld data without having to consider the actual tool's structure and composition. We use a dispersion correction example to demonstrate an application of the simple theory to fi eld data processing and the validity of the processing result.

Study on Shear Velocity Profile Inversion Using an Improved High Frequency Constrained Algorithm

“…When using real logging data to invert the formation's S-wave velocity radial profile, the impacts of the acoustic logging tool cannot be ignored. Due to a complex structure, the equivalent-tool theory can be introduced to simulate the impact of the tool [17]. Assuming that the logging tool is a cylinder with a radius of a, no matter how complex the structure of the tool is, as long as the wavelength of the bending wave is greater than the radius of the tool, the tool can be equivalent to an elastic rod with an elastic modulus of M T .…”

“…Meanwhile, the existing two inversion methods of the formation's S-wave velocity radial profile do not consider the impacts of the tool on the dispersion, which affects the processing effect of the real data. In this case, an equivalent-tool theory was proposed to eliminate impacts of the tool on the flexural wave dispersion in the dipole acoustic logging, and it has been effectively applied in filed data processing and formation information-extraction [17,18].…”

An ARM-based debugging system for multi-pole array acoustic logging tools

“…Multi-pole array acoustic logging (MPAL) is one of the most advanced acoustic logging technique that has been successfully developed and applied to the field of oil and gas exploration and production (Chen and Tang, 2012;Ju et al, 2008;Lu, 2007;Lu et al, 2008;Qiao et al, 2011;Su et al, 2011;Tang et al, 2007;Tang and Cheng, 2004;Tang and Patterson, 2009;Tang and Wei, 2012;Wang et al, 2012;. In the production of MPAL tools, verification and calibration are important processes that ensure the feasibility and overall performance of the tool.…”