Steering tool

The kick-off procedure required numerous single-shot runs to start the deviation in the correct direction. Since, during this phase, the drillpipe was not rotating a steering tool was developed to be lowered on an electric wireline instead of the single shot. The measurements were then made while drilling. 

Figure 4-215. Typical steering tool unit with surface panel and driller readout. (Courtesy of Institut Francois du Petrols.)...

Figure 4-216 shows the typical operation of a steering tool for orienting the drill bit. The electric wireline goes through a circulating head located on top... 

Figure 4-218 shows the arrangement of the sensors used in a steering tool. Three flux-gate-type magnetometers and three accelerometers are positioned... 

Figure 4-217. Typical operation of a steering tool for orienting the driil bit using a side-entry sub. (Courtesy SPE [101].j...

Figure 4-218. Sketch of the principle of the sensor arrangement in a steering tool and any magnetic directional tool. (Courtesy SPE...

The steering tools have practically been abandoned and replaced by MWD systems, mostly because of the electric wireline. However, the high data rate of the electric wireline (20-30 kbits/s) compared to the low data rate of the MWD systems (1-10 bits/s) make the wireline tools still useful for scientific work. 

Magnetometers. Magnetometers used in the steering tools or MWD tools are of the flux-gate type. 

Example 1 Steering Tool Measurements—Tool Face, Deviation... 

Single-axis accelerometer systems are used in the steering tools and MWD tools for inclination and tool face data acquisition. Using a spreadsheet, compute the current values for each accelerometer in the following cases ... 

Example 2 Steering Tool Measurements— Tool Face, Deviation, and Azimuth... 

A steering tool is normally used during drilling with a mud motor and is connected to the surface with an electric wireline. The sensing devices shown in Figure 4-232 are also used in most MWD mud pulse systems. The coordinates... 

Figure 4-232. Schematic view of the sensor arrangement in a steering tool.

Example 4 Steering Tool Measurements—Trajectory Forecast... 

An interesting problem that can be solved with the steering tool or the MWD measurements is the trajectory forecast when drilling ahead with a given bent sub (constant angle), and a given tool-face angle. 

Note We will assume that the borehole axis is the same as the drill collar axis at the steering tool depth and also that the borehole axis is the same as the mud motor axis at the mud motor depth. 

A steering tool sensor and electronic package is mounted in a housing in Figure 4-238 with a shock absorber and a spring to decrease the value of deceleration when engaging the mule shoe. 

Retrievable Tools. Retrievable MWD tools similar to the steering tools are available from several service companies. They are generally battery powered and generate coded positive pressure mud pulses or continuous pressure waves. The lower part of the tool has a mule shoe that engages in a sub for orientation. Currently, tools are available for measuring directional parameters and gamma rays. A typical retrievable tool is shown in Figure 4-251. 

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