Magnetic and Gravity Toolface and How To Interpret The Meaning For Directional Drilling

Magnetic and gravity tooสface are terms in directional drilling world to describe the direction of the well. They are different in meaning and application therefore this article will teach you about these terminologies and how to read it.


Magnetic Toolface
The magnetic toolface is an angle projection onto the horizontal plane between the tool face and magnetic north. Typically, directional tools use the magnetic tool face when the inclination is less than 5 degree. The Figure 1 demonstrates that the mud motor is lined up to kick off at 30 degree azimuth magnetic.

Figure 1 - Magnetic Toolface
Figure 1 – Magnetic Toolface Continue reading

Applications of Directional Drilling in Oil and Gas Industry

Directional drilling is an advance drilling technique which can deviate wellbore to the planned trajectory in order to reach the reservoir targets. Nowadays, directional drilling is widely used around the world because it has several advantages over a normal vertical well. Oil and gas reservoir shapes has the lateral length more than vertical length so the directional drilling will have more opportunities to reach potential sands. Ultimately, hydrocarbon reserves can be extracted with the directional wells. The applications of directional drilling are as follows:

application of dd

Sidetrack Well


Sidetrack is the process to drill a secondary well from an existing wellbore. Directional drilling technique is applied to successfully side track. There are advantages of sidetracking well as bypassing fish, kicking off from cement plug, extend of the producing zones, etc.

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Directional Drilling Handout from Texas AM

I would like to share very useful Power Point slide in the topic of directional drilling which is belong to Texas A&M university, USA.

Directional Drilling

When is it used?

Type I Wells (build and hold)

Type II Wells (build, hold and drop)

Type III Wells (build)

Directional Well Planning & Design

Survey Calculation Methods

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Survey Calculation Methods –

Radius of Curvature

Balanced Tangential

Minimum Curvature

Kicking Off from Vertical

Controlling Hole Angle (Inclination)

Survey Calculation Methods

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Directional Drilling  Continued

 Tool-Face Angle

Ouija Board

Dogleg Severity

Reverse Torque of Mud Motor

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The Wellbore Trajectory Control –

Bent Motor and Bent Sub


Directional Drilling Measurements

Single Shot and Multishot

Magnetic and Gyro

Steering Tools

MWD tools

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What are the differences between steering (orienting or sliding) and rotating?

Steering (orienting or sliding) is drilling with mud downhole steerable mud motor. Drilling with the steerable motor does not rotate drill pipe because it uses hydraulic power to drive down hole motor and bit. Steering is used in order to control well direction.

Rotating is drilling with Topdrive or rotary table and drillstring is rotated in order to gouge the hole. Rotary drilling will be used when straight hole direction is needed.

Comparing between steering and rotating, steering can create dog leg more than rotating because mud motor incorporating with bend housing is designed to directionally drill to the specified direction; however, when Rotating, BHA is stiffer and has tendency to hold the direction.

Rotating ROP is always faster than steering ROP by these following reasons:
• Friction force exerts on stable drill string when steering is always more than rotating.
• When steering, WOB is limited. Motor can be stalled or worn out if WOB excesses.
• Direction of well must be controlled carefully that means well can not be drilled faster.

Reference books: Directional Drilling Books