Design and performance evaluation of phased parametric array for the detection of geological conditions ahead of drill bit

The detection of the reflectors ahead of drill bit in oil drilling well is vital in ensuring the safety production and realizing well geosteering. In order to achieve the objective, a phased parametric array is designed and the performance is evaluated by simulating wave propagation in a drilling well with reflectors ahead of the drill bit. According to self-demodulation effect of sound field excited by parametric array and phased array method, a phased parametric array with particular parameters is designed by taking into account the conditions in the drilling well. Supposing that acoustic signals are emitted from the parametric array in the borehole, wave propagation of the signals in the drilling hole underground are investigated by using 3-D finite difference method in cylindrical coordinates, where the propagation mechanism of waves in the borehole, the formation surrounded and the reflectors ahead of the drill bit are studied in detail by analyzing the synthetic data. The numerical results and analysis show that geological information of the reflector such as the distance from the bit derived from the waveforms agrees well with the numerical model. The work indicates that a properly designed phased parametric array has the potential to be used in detecting geological conditions ahead of the drill bit.