Evolution in Reliability of High-Speed Mud Pulse Telemetry

Abstract

Mud pulse telemetry (MPT) is the leading real-time data transmission technology in the oil industry to deliver answers while drilling. New logging-while-drilling (LWD) tools produce increasing amounts of data that has to be transmitted to the surface. To avoid a compromise between rate of penetration (ROP) and log density, the real-time data rate has to increase. This is particularly true when demanding mud environments create demanding transmission conditions for MPT. As the well depth increases, it affects the mud density and mud plastic viscosity, making the situation even more challenging. This paper describes evolutionary changes to a MPT system. The system uses a special training sequence (TS) that is regularly sent by a shear valve pulser. Surface controls detect the TS and use it to tune, automatically, adaptive filters. These filters respond to the current channel conditions, enabling reliable physical data rates of 10bit/s and greater. To avoid decreasing the decoding quality due to non-optimal filters that have been calculated during pressure/flow disturbed transmission, the system automatically tests the performance of all filter sets. Afterwards, the coefficients are saved into a database with additional information. This empowers the field service engineer to perform a quick look at the database and maintain high decoding quality. Sophisticated changes to the TS and to the surface algorithms have significantly improved the automated detection rate of the TS search. Compared to offset runs in challenging fields, decoding quality and reliability have improved. The introduction of higher automation levels enables field personnel to deliver more answers to the operator, and provide multifaceted bottomhole assemblies with many LWD services. By eliminating the tradeoff between ROP and log density through higher data rates in MPT, the overall cost of drilling wells decreases without compromising safety.