Implementation and Performance of Valve-Controlled Encoding in Fluidic Wave Communication

Abstract

Wireless layered water injection technology using fluidic waves as a communication medium features a simple tubular structure and strong process adaptability. However, when relying solely on pressure waves, issues such as low communication efficiency and insufficient success rate of uplink data arise. This paper proposes using flow rate waves as the primary communication medium and developing a new communication encoding based on the transmission characteristics under valve control to improve these issues. Based on the transmission characteristics of fluidic waves, this study developed a novel fluidic wave signal generator to produce well-defined waveforms. Considering the differences in power supply and maintenance between surface and downhole, a binary encoding scheme was designed for downlink instructions, while a duration-based encoding scheme was developed for uplink data. The binary encoding adopts a concise unipolar non-return-to-zero format, derived from the correspondence between valve actions and the generated waveforms. The pulse-width encoding utilizes the high similarity between rising or falling edges of the waveforms, representing production data through the time intervals between these consecutive edges. This study presents a signal generator and its control coding scheme, tested on a dedicated bench. The key findings are: 1) Higher switching repeatability yields more stable sensor waveforms for reliable decoding. The implemented generator, with a high-precision absolute angular displacement sensor (0.2° resolution) and control software, achieves a maximum repeatability error of 0.4°. 2) Compared to Manchester coding, the proposed binary coding avoids level jumps for consecutive identical bits, reducing valve switching frequency, wear, and power consumption while enhancing transmission accuracy. 3) The adopted pulse-width encoding transmits one data unit per pulse, further minimizing downhole valve operations. This extends the maintenance-free period of downhole tools beyond five years and enables high-precision production data acquisition (e.g., flow rate error <1%). Based on the fluidic wave transmission characteristics under valve control, the developed signal generator and its control coding not only enhance communication efficiency and success rate but also reduce power consumption. This provides higher reliability and an extended maintenance-free period for battery-powered wireless communication in layered water injection technology.