A Gyroscope is a wheel that spins around one axis but can rotate about one or both of the other axes since it is mounted on gimbals. The inertia of the spinning wheel tends to keep its axis pointing in one direction. Therefore, gyroscopic instruments use this spinning gyro to determine the direction of the well. There are four kinds of gyroscopic tools: conventional gyro, rate or north-seeking, ring laser, and inertial grade. In situations where magnetic survey instruments are unsuitable, such as in cased holes, the gyro can be an alternative tool.
The survey tool used in the oil and gas industry rotates a gyroscope with an electric motor at around 40,000 rpm. The tool aligns with True North on the surface and ensures that the gyroscope remains pointing in that direction as it runs into the hole, regardless of any forces that may attempt to deflect it.
A compass card is attached to and aligned with the gyroscope’s axis; this acts as the reference direction for all directional surveys. Once the tool has landed in the required position in the drill collars, the procedure is very similar to that for the magnetic single shot. Since the compass card is linked to the gyroscope’s axis, it records a True North bearing, which does not require correction for magnetic declination.
Film-Based Conventional Gyro
As mentioned, a film-based conventional gyro is available as a single-shot instrument. In areas where magnetic interference is present, like in cased holes or near other wellbores, film-based gyros are no longer commonly used for surveying and positioning deflection tools in oil and gas. Nowadays, gyros are typically run as multi-shots on an electric wireline. In addition, a computer is handling the information processing at the surface. Deflection tools can also be oriented by wireline gyros. Gyros are also available in measurement while drilling tools.
Gyro Tool Operating Forces
To understand the forces operating on gyroscopes, let’s begin by analyzing simplified gyroscopes. Simplified gyroscopes have frames called gimbals that support the gyroscope and enable freedom of rotation.
As the probe moves downhole through different directions and inclinations, the gimballing allows the gyro to attempt to maintain a horizontal orientation in space.
In performing a wellbore survey, the gyro is pointed in a known direction before running in the well, so throughout the survey, the spin axis attempts to hold its surface orientation. Note that a compass card is aligned with the horizontal spin axis of the gyro. Survey data is collected downhole by affixing a plumb-bob assembly over the compass.
At each survey station, a picture of the plumb-bob direction concerning the compass card is taken, resulting in wellbore azimuth and inclination readings. The plumb-bob always points down toward the Earth’s center as a pendulum. When the tool is inclined vertically, it points out the inclination of the well on the concentric rings and the azimuth by correlation with the known direction of the gyro spin axis established at the surface. (Note: Electronic, surface read-out free-gyro systems also eliminate the plumb-bob.)
Application Of Gyro Tool In Directional Drilling Surveying
Compass readings are typically used to determine the well’s direction when conducting magnetic surveys. However, these readings can be unreliable in cased or open holes near cased wells. In such situations, an alternative method is necessary to assess the well’s direction accurately. A gyroscopic compass can be used to evaluate the well’s inclination similarly to magnetic tools, but it eliminates the magnetic effects that can interfere with accuracy.
The gyroscope inclinometer from Vigor uses a solid-state gyro sensor for measurement, and the microstructure of the solid-state gyro sensor is very complex, for which the choice of material, process flow and machining accuracy are very important. The process makes solid-state gyro sensors more efficient, consumes less power, and is smarter. Gyroscope inclinometers can withstand very harsh downhole environments, including severe shock and vibration. In addition, good measurement performance can be achieved even under magnetic interference.
Vigor’s gyro inclinometer product can meet various oil and gas well orientation and trajectory requirements such as high precision, high speed, high temperature, small borehole, short radius well, horizontal well, tunnel crossing, etc. In addition, it can also be used in fields such as near-well anti-collision control and magnetic permeability, which can reduce the risk of well collisions in dense well clusters, optimize drilling trajectories, and reduce engineering costs.
For more information, you can write to our mailbox info@vigorpetroleum.com & marketing@vigordrilling.com
