A pressure pulse recognition method based on flow-adaptive double threshold for pressure pulse telemetry

Pressure pulse telemetry as a novel and effective method of communication has received more and more attention in the field of separate layer water injection for the intelligent oilfield, and identification of the effective pulses and their positions is one of the key technologies. For the logging while drilling process, the fixed threshold method is widely used to identify the pressure pulse. However, in the process of water injection, the amplitude of pressure pulse changes with the change of flowrate controlled by process, which will lead to low recognition rate of traditional fixed threshold pressure pulse. Therefore, a pressure pulse recognition method based on flow-adaptive double threshold with fixed time window is proposed. The packet length of instructions and responses is designed to be short and fixed in order to reduce communication time and failure cost, and the fixed time window method is adopted to improve the decoding efficiency of for a frame of data. The pressure pulse recognition method based on flow-adaptive double threshold is used to identify the effective pulses and their positions to adapt to the change of pressure pulse amplitude induced by different flowrates. The first threshold which is set to fixed and lower than the pulse peak with minimum possible flowrate, is used to filter the most of noise and catch the effective pulses with little noise pulses. The second threshold which is adaptive to changes of the flowrates, is determined by average of three maximum peaks of caught pulses from the first threshold, and is used to identify the effective pulses and their positions. In the experimental well with 2000 m deep, the test results show that the error rate of pulse recognition reduce to 0.003% and communication success rate significantly increase from 50% to more than 96.5%. It means that the proposed double threshold method can be adaptive to identify effective pressure pulse under different flowrates, and then can significantly reduce the error rate of pulse recognition and improve two-way communication performance between the wellhead controller and downhole distributors.