Downhole Pressure Wireless Monitoring via Electromagnetic Waves Transmission in Oil Well Production

Abstract Pressure monitoring is one of the crucial dynamic parameters in the production process of oil wells. Due to the large number and wide distribution of oil wells, the use of wired monitoring technology aims to reveal downhole production dynamics in some high-production-rate or key wells, there are difficulties such as high production costs, large analysis workload, high risks, and maintenance of monitoring tools, which are not suitable for large-scale promotion. The lack of intuitiveness and timeliness in conventional storage pressure monitoring has brought enormous difficulties to the normal management of oil wells. However, the wireless data transmission method of Electromagnetic Waves Measurement While Drilling (EM-MWD) cannot be directly implemented into oil production wells. On the basis of technical research and drawing on the wireless monitoring experience of EM-MWD, the 3 different electromagnetic wave excitation methods were compared, and an asymmetric oil tube antenna electromagnetic wave excitation method suitable for matching the characteristics of the pumping well was identified. Mathematical models of the wellbore formation were established. Based on finite element analysis, a simulation model of electromagnetic wireless monitoring under the pumping well was constructed, and the influencing factors of electromagnetic wave transmission were analyzed, including the influence of formation wellbore, casing, and well fluid media on electromagnetic waves. After conducting research on the structural principles and weak signal processing methods, a wireless monitoring system for ultra-low frequency electromagnetic wave downhole monitoring data, combined with downhole electromagnetic wave transmitter and surface receiver for pumping wells, is formed. By installing a transformer on the output end and adjusting the voltage, the simulated test ground can achieve electromagnetic wave signal acquisition at a depth of 1500 meters and meet the analysis requirements. Through on-site testing at X well, when the well depth reaches 1517m, the signal can be transmitted normally; The signal acquisition frequency band of the wireless transmission system for underground pressure is once per 5-1440 minutes, and the pressure measurement range is 0-100MPa; The accuracy of downhole measured pressure data by sensors reaches 80%. The development of a wireless monitoring system for downhole pressure in pumping wells is of great significance for dynamic monitoring of reservoir pressure and intelligent reservoir construction. Downhole dynamic monitoring achieves intuitive and timely monitoring, providing a new tool for real-time understanding and mastery of reservoir dynamic changes; Compared to conventional cable control monitoring methods, it is expected to significantly reduce costs and help promote on-site application.