High-Temperature Acoustic Fluid Velocity Sensor Development

Abstract

Abstract There are numerous challenges to developing sensors for high-temperature and high-pressure hydrocarbon reservoir fluid analysis applications in the downhole environment. These challenges include material selection as well as processes for manufacturing, testing, and verification of the sensors. We were tasked with developing sensors for the analysis of subsurface formation fluid samples that required reliable operation up to 38,000 psi (262 MPa) and 450° F (232° C). This paper focuses on the technical challenges and our solution for one such sensor that measures the sound speed of the sampled formation fluid. The core of our acoustic transducer is a piezoelectric crystal, which serves as the acoustic transmitter and receiver. This paper-thin, coin-shaped crystal has even thinner silver electrodes deposited on both of its faces. Numerous wire-to-electrode bonding methods were investigated, which included soldering, sintering, and epoxying, the latter of which proved successful.