We describe a wireless microsystem for gastrointestinal manometry that couples a microfabricated capacitive transducer to a dual-axis inductor, forming a resonant inductor-capacitor (LC) sensor within an ingestible 3D printed biocompatible capsule measuring ø 12 mm × 24 mm. An inductively coupled external telemetry unit wirelessly monitors the pressure dependent resonant frequency of the LC sensor, eliminating the need for integrated power sources within the ingested capsule. In vitro tests in saline show pressure response of −0.6 kHz/mmHg, interrogation distance up to 6 cm, and resolution up to 0.8 mmHg. In vivo functionality is validated with gastrointestinal pressure monitoring in a canine beagle over a 26-hour period.

This paper describes the design, implementation, and evaluation of an environmental logging microsystem (ELM) for operation at elevated pressure and in corrosive environments, at temperatures up to 125°C. The ELM units are intended to be deployed in large quantities, allowed to collect data, and then retrieved, interrogated, and re-charged. Powered by a rechargeable battery embedded within the system, each ELM incorporates pressure and temperature sensors, control electronics, optical communication elements, and power management and battery recharging circuits. The pressure sensor is a customized capacitive transducer chip on a sapphire substrate; details are provided in a companion paper. The electronic components and battery used in ELM are selected on the basis of functionality and form factor; packaged components are selected for ease of assembly and for added protection against the environment. The pressure sensor, electronics and battery are assembled on a flexible circuit board, folded into a stack with dimensions 7.2 mm × 6.6 mm × 6.5 mm, and encapsulated in a steel tube filled with optically transparent silicone caulk. This encapsulation provides mechanical protection against shock and abrasion, as well as chemical protection against high salinity environments, while allowing the ambient pressure and temperature to be transferred to the sensing elements. Results are reported from high-temperature and high-pressure tests reaching 125°C and 7,250 psi in brine and other corrosive environments in laboratory conditions. Field tests that were conducted in a brine well to a maximum depth of 1,235 m are also described. The recorded data were post-processed to interpret the environmental pressure and temperature.

Using distributed MEMS pressure sensors to measure small flow rates in high resistance fluidic channels is fraught with challenges far beyond the performance of the pressure sensing element. In a typical core-flood experiment, which may last several months, flow-induced pressure gradients are generated in porous rock core samples wrapped in a polymer sheath. Measuring these pressure gradients along the flow path requires high resolution pressure measurement while contending with difficult test conditions such as large bias pressures (up to 20 bar) and temperatures (up to 125 °C), as well as the presence of corrosive fluids. This work is directed at a system for using passive wireless inductive-capacitive (LC) pressure sensors that are distributed along the flow path to measure the pressure gradient. The sensors are wirelessly interrogated with readout electronics placed exterior to the polymer sheath for continuous monitoring of experiments. Using microfabricated pressure sensors that are smaller than ø15 × 3.0 mm3, an LC sensor design model for minimizing pressure resolution, accounting for sensor packaging and environmental artifacts is investigated and experimentally validated. A test setup, built to provide fluid-flow pressure differentials to LC sensors with conditions that mimic placement of the sensors within the wall of the sheath, is used to test the system. Experimental results show the microsystem operating over full-scale pressure range of 20,700 mbar and temperatures up to 125 °C, while achieving pressure resolution of <1 mbar, and resolving gradients of 10–30 mL/min, which are typical in core-flood experiments.

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 &lt;25 cm3 and density &lt;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 &gt;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.

An innovative and practical solution for well monitoring of pressure, temperature, inertial, and magnetic parameters is reported. Tiny and robust systems integrating microscale technologies for telemetry, wireless charging, and physical sensing were developed, characterized, and ultimately deployed on a live installation. The microsystems were designed and developed by the University of Michigan and characterized by Total S.E., whereas the intervention protocols were designed and implemented by TOTAL in TOTAL E&P CONGO offshore facilities. This work demonstrates how regular downhole monitoring of assets can be performed at low cost, thus optimizing production while also de-risking future development plans such as infield wells. This novel approach also reduces risks associated with conventional downhole monitoring methods.