Novel Use of Application-Specific Integrated Circuits in Quartz-Based Permanent Downhole Gauges Increases Reliability Estimates in High-Temperature Applications

Abstract

Abstract This paper demonstrates the benefits of using application-specific integrated circuits (ASICs) in the design for downhole, quartz-based, pressure and temperature permanent downhole gauges (PDGs). Historically, downhole electronics have been built with general purpose chipsets, whose functions areadapted to suit design needs. In contrast, through integrating and optimizing the necessary functions into a single integrated circuit (IC), ASIC technology enables a chipset to be customized for a particular use. Compared to the previous generation of PDGs, this approach reduces the overall footprint of the gaugeand improvesthe overall gauge performance,especially for reliability performance. Suchimproved reliability performance is validated through the use of the design for reliability (DFR) process, which consists of define, identify, verify, and validate stages. Thecoreof the validate stage is thereliability demonstration test (RDT). The detailed advantages of the novel use of ASIC technology in PDGs are discussed in this paper, with comparison to the previous generation of PDGs. The incorporation of ASIC circuitry enables lower current consumption, which in turn enables deployment of an increased quantity of pressure and temperature PDGs without increasing the system's power budget. The implementation of ASIC technology helps reduce the overall size of the PDGs, with a 67% reduction in length and a 44% reduction in outer diameter (OD), which also enables direct integration to tubing encased conductors (TEC) by means of prewelded and prespooled connections.The RDT results demonstrate that the ASIC-based PDGcan at least triple the operationlifetimecompared to the previous generation of PDGsin high-temperature downhole environments. Overall, the adoption of ASIC technologysignificantly improves the reliability of PDGs, demonstrating a life of 10 years at 175°C with 80% reliability and 60% confidence in accordance with industry recommended practices, andprovides a permanent downhole monitoring system with a deployment of 40 or more gauges for high-pressure/high-temperature (HP/HT) applications.