Бурение грунтовых зондов, установка энергетических колодцев

All MWD systems use basically the same directional sensors for calculating inclination, azimuth and tool face. The sensor package consists of 3 orthogonal accelerometers and 3 orthogonal magnetometers (Figure 3).

An accelerometer will measure the component of the earth’s gravitational field along the axis in which it is oriented. It works on the “force-balance” principle. A test mass is suspended from a quartz hinge which restricts any movement to along one axis only (Figure 4). As the mass tends to move due to gravity acting along

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that axis, its central position is maintained by an opposing electromagnetic force. The larger the gravitational force, the larger the pick-up current required to oppose it. The voltage drop over a resistor in the pick up circuit is measured, and this is directly related to the gravitational component. Depending on the orientation of the BHA the reading on each accelerometer will be different. From these 3 components the angle of inclination and tool face can be calculated (Equations 1 and 2).

A magnetometer will measure the component of the earth’s magnetic field along 1 axis. If a wire is wrapped around a soft iron core (Figure 5) and then placed in a magnetic field, the current induced in the pick-up circuit will vary depending on the angle at which the toroid is placed. Therefore the size of current is related to the direction of the coil with respect to the direction of magnetic field. As with the accelerometer the voltage is measured across a resistor in the pick — up circuit of the magnetometer. The voltages read at each magnetometer can then be used to calculate azimuth (Equation 3).

Phase shift or remain

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