Donald J. Milligan

Hewlett packard's seismic grade MEMS accelerometer

HP has recently made its plans to develop an ultrahigh-resolution seismic sensing solution public. This solution is being developed with Royal Dutch Shell Corporation for oil and gas exploration [1]. Central to delivering this system is HPs new single axis seismic grade MEMS accelerometer. The HP device uses both bulk micromachining methods and standard thin film technologies as well as HPs new three phase sensing technology. This sensor detects motion when an array of electrodes located on the proof mass moves relative to a stationary array of electrodes across a fixed gap. Initial characterization shows a flat noise power spectral density of < 100 nG/vHz over a bandwidth of DC-200 Hz. The device exhibits a linear response to +/− 150mG with a sensitivity of over 25 V/g within the specified bandwidth.

An ultra-low noise MEMS accelerometer for seismic imaging

A new MEMS capacitive accelerometer has been developed to meet the requirements for oil and gas exploration, specifically for imaging deep and complex subterranean features. The sensor has been optimized to have a very low noise floor in a frequency range of 1–200 Hz. Several design and process parameters were modified from our previous sensors to reduce noise. Testing of the sensor has demonstrated a noise floor of 10ng/√Hz, in agreement with our predictive noise models. The sensor has a dynamic range of 120db with a maximum acceleration of +/− 80mg. In addition to the performance specifications, automated calibration routines have been implemented, allowing bias and sensitivity calibrations to be done in the field to ensure valid and accurate data. The sensor frequency and quality factor can also be measured in the field for an automated sensor health check.