Definition - What does 3-Axis Accelerometer mean?
A 3-axis accelerometer is used to calculate the pitch and roll of the drilling bit.
The 3-axis accelerometer consists of three -5 to +5g accelerometers that are mounted on a block. It measures the three mutually orthogonal components of the acceleration of gravity for a stationary drill bit.
The attitude information includes the pitch, roll, and azimuth of the drilling bit. By measuring the acceleration due to gravity, an accelerometer calculates the angle of tilt with respect to the earth and the velocity and direction of the drill bit.
To compensate for errors, two redundant accelerometers fixed at two different planes are used.
Trenchlesspedia explains 3-Axis Accelerometer
The 3-axis accelerometer is used in conjunction with compatible software. Inertial guidance systems use fiber-optic gyroscopes along with highly sensitive accelerometers to locate the drill head precisely along the borepath.
The connection of the optical gyro system from downhole to the surface is done via a transmission system that sends the pitch, roll and azimuth readings three times in a second providing the engineer with real-time measurements.
The pitch and the azimuth should be determined during the drilling process to operate the drilling machine economically hence using the term measurement while drilling or MWD.
The inertial guidance system is used for drilling head guidance in trenchless construction methods of vertical drilling and horizontal directional drilling (HDD) and relies on knowing the initial position, velocity, and attitude.