Downhole Analogue Quartz Gauge

Wood Group Production TechnologyProduction Technology's permanent downhole analogue quartz gauge is field proven since the early 1990s. Following this, our digital quartz gauge was first introduced in 1995, allowing multiple sensors on the same cable, and providing a field-proven platform for new sensors. Our standard downhole gauges - Analogue (ROC-A) and Digital (ROC-D) - incorporate a resonating quartz crystal with a well-proven record in downhole applications.

Further improvements under our Quality Improvement Programme have been implemented to produce our completely revised next generation digital quartz gauge - the ROC system. The digital model can be configured for multiple pressure and temperature nodes

The quartz pressure sensor is a thick-walled, hollow cylinder with closed ends. A thickness shear mode resonator divides the central position of the hollow cylinder. Fluid pressure on the exterior walls compresses the cylinder, thus producing compressive stress in the resonator, which changes its resonant frequency. The transducer assembly includes the pressure sensor crystal, a temperature sensor crystal and a precision reference crystal and electronic circuitry.

The gauge electronics convert the resonator frequencies to a proprietary protocol prior to transmission to surface. The transducer and electronic circuitry are housed in stainless steel to NACE MR-01-75 standards and contained in an Argon filled housing to prevent moisture contamination. All primary seals are electron beam welds, or metal to metal seals with elastomeric back ups.

All gauges, once constructed, are required to pass thorough Environmental Stress Screening (ESS) to highlight any defect in the functionality, prior to installation at the well site. This method of screening has proved to be far more effective than traditional "burn-in" techniques.
The downhole cable is terminated to the top end of the gauge and is metal sealed between the cable sheath and the gauge. This seal is pressure tested once the cable is terminated to the gauge at the well site.

Benefits
• reliability
• field-proven system
• strict quality control
• redundancy (ROC-D)
Applications
• conventional oil / gas environments
- subsea, platform, land
- standard/horizontal tree
• ESP Monitoring
• EWT/EPF
• Fracture Monitoring
Features
• industry standard quartz resonating sensor
• robust
• cost-effective
• multi-point sensing (ROC-D)

<%=company%>, 16700 Park Row, Houston, Texas 77084. Phone: 281-492 0309; Fax: 281-398 3410.