Downhole navigation systems are continually evolving, bringing greater precision, reliability, and time savings. Drilling multiple wellbores in close proximity from drill pads runs the risk of well collision and drilling complex trajectories toward targets at ever-increasing depths requires accurate, dependable survey equipment. Incorporating an inertial, north-seeking gyro surveying instrument into a directional drilling system seems a natural step.

Sweden’s Stockholm Precision Tools AB (SPT) has developed a high-speed directional drilling system that uses gyro compassing to determine direction. The Gyro Tracer Directional system is based on a north-seeking gyroscopic module. It directly measures the Earth’s rotation, finding the true geographic north. This makes it more accurate than alternative tools which utilize indirect measurement methods, such as microelectromechanical systems (MEMS).

Processing software integrated into the Gyro Tracer Directional tool allows operators to observe real-time drill surveying and to direct control of measurement-while-drilling (MWD) systems.

Advantages

Unlike other downhole survey or magnetic tools, the Gyro Tracer Directional is not affected by magnetic interference. It can be run inside casing, tubing, drill pipe and magnetically disturbed ground. The downhole autopilot capable of correcting itself along a survey path, eliminating drift and resulting in accurate surveying.

The streamlined, 42.9-mm-diameter system is only 1.8-m-long (including cable-head)?much shorter than other directional systems, which are typically 8 m long.

The Gyro Tracer Directional can be run in a variety of applications from shallow borehole to deep borehole surveying, single shot/multi shot, slimhole casing, orientation, whip stock kick-off, and downhole motor orientation.

Calibration

The new system is an improvement over other continuous north-seeking gyro-based tools because it runs faster and saves time. The Gyro Tracer Directional does not require surface calibration or start reference. Like SPT’s Gyro Tracer system, only the latitude is required.

The tool is placed into the drill collar or wellhead and one stationary survey is taken. The instrument then travels up to 130 m/min to the bottom of the hole without stopping, taking continuous north-seeking measurements. The Gyro Tracer Directional does not require in-hole drift checks. A second stationary is taken at the bottom of the hole and the instrument travels back up the hole up to 130 m/min on the out-run.

Repeatable performance

In a recent test, three different SPT systems were used in the same wellbore with the same programmed drill location. Not only did all three systems follow the same drill path, but there was zero drift (Figure 2).

Dual modes

The Gyro Tracer package comes with options to run in wireline or memory mode. Wireline mode is run from an electric line cable transmitting real-time data to the computer at the surface. Mono or multiple conductor cable can be used. Memory mode is fast and cost-efficient, battery-powered, and run on a slick line.

SPT has been developing survey technology since 1990.

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