WELLOG

WELLOG MEMS

Revised 5-22-2008

WHAT ARE MEMS DEVICES?

MEMS are surface-micromachined integrated-circuit accelerometers. The device consists of two surface micromachined capacitive sensing cells (g-cell) and a signal conditioning ASIC. The g-cell is a mechanical structure formed from semiconductor materials (polysilicon) using semiconductor processes. It can be modeled as a set of beams attached to a moveable central mass that moves between fixed beams. The moveable beams can be deflected from their rest position by subjecting the system to an acceleration. As the beams attached to the central mass move, the distance from them to the fixed beams on one side will increase by the same amount that the distance to the fixed beams on the other side decreases. The change in distance is a measure of gravitational acceleration.

MEMS devices have recently found many applications in electronics. WELLOG is finding many applications for these devices in the well logging industry.

WHAT DO THEY LOOK LIKE?

Click here à ADXL213

Click here à MEMS PCB for a view of a 3-axis MEMS printed circuit board currently in use.

WHAT CAN THEY BE USED FOR?

MEMS sensors produce an output that is related to gravitational force. The output decreases by an amount equal to the angle of deviation from the vertical component of gravity. WELLOG uses a proprietary design concept to create a linear angular output that has resolving capability to one tenth of one degree. Compass systems with tilt compensation are now available at WELLOG.

Typical logging with deviation tools uses the following procedure: The tool is calibrated before entering the well. Next, the tool is lowered to the bottom of the well. Deviation readings are taken at predetermined foot or time stations in the well. A Deviation log may contain readings taken at hundreds or thousands of stations. See the webpage on Deviation.