Acoustic source characterization for a logging while drilling tool: Theoretical and experimental modeling

Abstract

The development of acoustic source technology has been an important task for acoustic logging while drilling (LWD) and various source designs have been implemented. Using a multipole wave expansion theory, this study demonstrates that a LWD acoustic source can be represented as a combination of monopole, dipole, and quadrupole constituents and characterized by the contribution of each constituent. The theoretical analysis is experimentally demonstrated with a cylindrical pipe simulating the LWD collar. The result of this study can be used to provide a method for evaluating the performance of a LWD acoustic source.

Design of a New Acoustic Logging While Drilling Tool

“…Acoustic transducers are used to realize energy transformations between alternating electric signals and sonic signals, and acoustic logging while drilling technology generates longitudinal monopole waves, dipole shear waves, and quadrupole waves by exciting the same four piezoelectric transducers of different frequencies and combination modes [ 6 , 36 ]. That is, the excitation circuit should produce at least three high-power signals of different frequencies.…”

“…Traditional acoustic logging proceeds after drilling and cementing; however, acoustic logging while drilling (LWD) not only rapidly obtains traditional acoustic logging messages, but also predicts the reservoir pressure to improve drilling security, and obtains formation messages to guide the drilling orientation [ 2 , 3 ]. To date, acoustic LWD technology has progressed from testing formation longitudinal waves (the 1990s) to shear waves (the 2000s), and lastly to formation directional characteristics (2010) [ 4 , 5 , 6 ]. The most representative tools are SonicScope of the Schlumberger company [ 7 ], SoundTrak of the Baker Hughes company, XBAT from Halliburton, and Crosswave of the Weatherford company [ 8 , 9 ].…”