Low Power Autonomous Microsystems for Oil Well Logging Application

Abstract:

Downhole environmental monitoring can provide significant benefits to the petroleum industry. The rapid development of semiconductor technology enables autonomous sensing microsystems to operate at extreme environments. By injecting these microsystems into the boreholes and retrieving them after deployment, the geophysical conditions in the area of interest can be obtained. Challenges include high temperature, high pressure, miniaturized system size and packaging.

This talk presents three generations of the environmental logging microsystem (ELM) for downhole geophysical logging applications. The first generation, ELM1.0, is designed for temperature logging. Each system consists of a power management circuit, a microcontroller with an integrated temperature sensor, and optical indicators. The electronics are integrated on a flexible printed circuit board and packaged in a steel shell. The ELM1.0 was tested at up to 125 °~C, 50 MPa in high salinity conditions. The second generation (ELM2.0 & ELM2.1) is upgraded from ELM1.0 by adding a micromachined capacitive pressure sensor for ‰ 50 MPa pressure. These systems are packaged in steel shells filled with transparent polymer for pressure transfer, and have a dimension of 9.5—9.5—6.5 . The third generation (ELM3.0) is upgraded from ELM2.0 with a power switch and a low-cost polyimide pressure sensor. Both ELM2.0 and ELM3.0 were successfully tested at up to 125 °~C, 50 MPa in corrosive environments using laboratory instruments, and in a brine well at a depth up to 1235 m. A progressive polynomial calibration method was used for interpretation of the pressure sensor data from these tests. In addition, the work on a high power micromachined RF switch is summarized. This switch can potentially be used for RF communication in the ELM.