Autonomous Sensing Microsystem with H2S Compatible Package and Enhanced Buoyancy for Downhole Monitoring

Abstract

Summary We report an autonomous microsystem intended for deployment in harsh fluid environments. The microsystem incorporates pressure, temperature, and inertial sensors and Bluetooth Low Energy (BLE) communication electronics; power is supplied via secondary battery, recharged using Qi wireless power transfer. Sensors and electronics are incorporated within a circuit board measuring ø26.7 × 1.5 mm3 which is embedded in a package with volume <25 cm3 and density <1200 kg/m3. The small size and density permit enhanced buoyancy control and deployment through narrow apertures. The package is comprised of a fluorocarbon elastomer VitonTM shell, which provides the necessary mechanical and chemical protection, and is filled with low bulk density cenospheres, which reduce the overall density while still allowing pressure to be transferred to the board-mounted sensor. This integration approach allows reclamation and repackaging of the electronics for rapid evaluation in a variety of harsh environments. Microsystems were tested in laboratory conditions at pressures up to 41.5 MPa and temperatures up to the battery limit of 85°C while successfully recording data for >96 hours. The VitonTM packaging was tested in H2S, diesel fuel, and 15% brine. Microsystems were then successfully evaluated in field deployment conditions in an oilwell to a depth of 1290 m, recording pressure, temperature, and inertial data.

Encapsulating and inkjet-printing flexible conductive patterns on a fluoroelastomer for harsh hydrocarbon fluid environments

“…Furthermore, there are some alternatives to FKM for use at high temperatures and that demonstrate chemical resistance i.e. perfluoro elastomers (FFKM) are specifically used for high-temperature applications >200 °C, 23 and AFLAS® (the trade name of the fluoroelastomer based upon an alternating copolymer of tetrafluoroethylene and propylene (TFE/P)) can resist temperatures up to 230 °C. 103 However, these elastomers are extremely expensive compared to FKM, thus considering the final applications, a balance between the cost of the material and its compatibility with the environment needs to be considered.…”

“…79 According to the chemical compatibility chart published by Chemours. 80 FKM also does not have excellent compatibility with H 2 S. However, some researchers have proven the effectiveness of FKM in certain concentration limits of H 2 S by developing and testing sensor packaging for a downhole monitoring microsystem, 23 and an O ring made from Viton extreme for pipelines valves. 86 In addition to H 2 S, FKM is not compatible with acetone, esters, amines, organic acids, acetic acid, methyl ethyl ketone (MEK), ethyl acetate, or highly polar chemicals.…”

“…This microsystem was encapsulated with an exterior fluorocarbon elastomer, Vitont, which provides chemical and abrasion resistance. 23 Sharma et al fabricated Vitont based microfluidics to deal with valves in pumps, mixers, and hydraulic systems where it is essential to have an elastomer that has the capability to handle oil and gases without leakage or swelling. 22 Lately, the application of fluoroelastomers as an encapsulant in flexible electronics has become popular among researchers.…”