Long-term stability and performance characteristics of crystalquartz gauge at high pressures and temperatures

摘要

Good long-term stability of high precision quartz pressure sensorsnis necessary for various applications ranging from pressure transientnanalysis to permanent monitoring systems for optimal reservoirnmanagement in the petroleum industry. A crystal quartz gauge (CQG1n) is a dual-mode, thickness-shear, quartz pressure sensor that hasnbeen used in oil field services for the past 8 years. High accuracy,nresolution, and fast response time of this sensor enable a reliablenestimate of formation permeability and oil/water interfaces innreservoirs that help reduce the overall cost of oil and gas production.nThe sensing resonator characteristics can be described in terms ofnequivalent circuit parameters (motional resistance and capacitance),nresonator-Q and the short-term frequency stability of both the B- andnC-modes of vibrations at various temperatures. The pressure readingnerrors of manufactured gauges are less than 8.89 kPa (1 psi) (plus 0.01%nof the reading because of the uncertainty of the dead-weight tester).nThe pressure resolution is better than 20.7 Pa (0.003 psi) over a 1-sngate time. An extremely effective dynamic compensation algorithm yieldsncorrected pressure readings with a very fast response time as short as anstrain-gauge-based pressure transducer while retaining the highnperformance of a quartz gauge. Recent long-term stability tests of CBGsnshow a negligibly small drift of the order of a few tenths of 1 psi (0.1npsi=689 Pa) at 103 MPa (15 kpsi) and 175°C for a period of more thann1 yr. These results confirm that the CQG characteristics exceed thendemanding specifications for both the well tests and permanentnmonitoring systems