Development and Testing of Acoustic Nipples While Drilling

In order to satisfy the requirement for real-time formation pressure monitoring and geomechanical parameters calculation, an acoustic nipple while drilling was developed based on the analysis of key technologies of acoustic measurement while drilling. The internal and external diameters of the nipple are 57.2 mm and 171.0 mm,respectively. It has one emitter and two receivers in operation mode. The emitting acoustic system is equipped with one monopolar sub-emitting transducer, and the receiving acoustic system is equipped with two receivers with four broad-band receiving transducers for each. The emitting and receiving acoustic systems consist of two separated parts. The spacing between the emitter and the receiver can be changed, but it is fixed at 200 mm among receivers. Based on the test of acoustic measurement,acoustic excitation frequency of emitting acoustic system is 12.92 kHz and its directivity pattern is similar to an ellipse. In the receiving acoustic system, the resonance frequency of eight receiving transducers is in the range of 30.84-33.53 kHz, averaging 32.23 kHz. The full wave form of the cased hole in the test was recorded by using the nipple and the acoustic measurement circuit while drilling, and the calculated acoustic velocity was 5 100 m/s. The successful development of the acoustic nipple while drilling will provide significant technical data for the development in China of acoustic logging devices while drilling.