Quartz thickness-shear mode pressure sensor design for enhanced sensitivity

Companies in the oil and gas industry rely upon acquisition of accurate downhole pressure data for management of reservoir resources. Pressure data must be acquired in extreme environments present in wells, including high pressures, high temperatures, and high levels of shock and vibration. A primary concern of oil and gas companies is that pressure transducers provide reliable data throughout the duration of well-testing jobs. Important performance parameters for well-test pressure gauges include inaccuracy arising from nonlinearity, hysteresis, nonrepeatability, and temperature. Accurate pressure measurements are required for determination of reservoir resources. Sensor output per unit pressure (sensitivity) and the corresponding minimum resolvable pressure (resolution) are important performance considerations. Pressure resolution is the key parameter for dynamic well-test analyses used to determine reservoir properties. Design limits, including maximum allowable pressure over the operating temperature range, also must be known. Pressure transducers must retain acceptable performance characteristics including accuracy, sensitivity, and resolution for long periods of operation to provide reliable data and reduce the frequency and cost of recalibration. This paper describes a unique quartz thickness-shear mode sensor that was developed for downhole pressure measurements. Pressure transducers that use this sensor meet the demanding requirements of downhole testing.