Efficient acoustic filtering for oilfield technology

Toshihiro Kinoshita , Naoki Sakiyama

Logging while drilling (LWD) acoustic measurement provides timely analysis for borehole stability and drilling optimization in the oilfield. An LWD acoustic tool is composed of a drill collar (thick steel pipe) equipped with an acoustic source and receivers to probe rocks surrounding the borehole. The drill collar area is favorable for tool wave propagation from the transmitter to the receiver section of the tool. Minimizing such arrival is critical to avoid unwanted interference with formation signal. In order to decrease such interferences, multiple grooves of different sizes are machined inside the drill collar. Non-homogeneity of the structure constructs a solid filter similar to a solid rod loaded with heavy masses. The stop-band and attenuation of the tool propagation largely depend on the distribution and size of the grooves machined into the collar. Their characteristics as an acoustic filter are also subject to properties of borehole fluid, where the drill collar is immersed. Therefore, the groove pattern has to be designed by modeling with consideration to many factors within given constraints. A method to optimize the groove pattern for given acoustic characteristics is discussed in this paper. The application to real data will illustrate the effectiveness of this methodology.

Mots clés: Solid filter; Logging while drilling

Domaines: Acoustique [physics.class-ph]

Toshihiro Kinoshita, Naoki Sakiyama. Efficient acoustic filtering for oilfield technology. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00810944⟩