The **tangential method** is the simplest calculation among other directional survey calculations.

The tangential method formulas are listed below;

The **tangential method** is the simplest calculation among other directional survey calculations.

The tangential method formulas are listed below;

The **Minimum Curvature Method** smooths two straight-line segments of the Balanced Tangential Method by using the Ratio Factor (RF).

The formulas for the Minimum Curvature Method are listed below;

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I have some **directional calculations** that I’ve shared with you. However, some of them are not shared yet so I will try to share all directional drilling formulas that may be helpful for you in the future.

Today, I would like to show you about** Balanced Tangential Method Calculation. **This calculation method treats half of the measured distance (MD/2) as being tangent to I1 and Az1 and the remainder of the measured distance (MD/2) as being tangent to I2 and Az2.

I created summary page for drilling formulas and calculations (http://www.drillingformulas.com/drilling-formulas-and-calculation-sheets/). I wish these excel sheets would be helpful for you.

Amount of cuttings produced per foot of hole drilled

Annular Pressure Loss

Annular-Capacity

Annular-velocity

Bulk Density Calculation

Buoyancy Factor Oilfield

Convert Pressure to Equivalent Mud Weight

Convert-Specific-Gravity

Cost Per Foot Calculation

Critical RPM

D Exponent Calculation

D Exponent Corrected Calculation

Decrease Oil Water Ratio

Density of Oil Water Mixture

Depth of Washout

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**Vertical Section** is the horizontal distance of wellbore that moves in the direction of the target per each station or in total. For instance, in the figure below, vertical section is the distance from survey to survey point and it’s measured in the same direction of the vertical section direction.

The two factors that affect vertical section are as follows:

1. The Incremental horizontal displacement (? HD)

2. Vertical section direction (VSD) is the azimuth that is used to reference to the vertical section. Normally, VSD is the azimuth of the last target.

The simple mathematics as Average Angle Method calculation demonstrates the relationship of the VS as below:

**VS = cos (VSD – Az avg) X ?HD**

VS: Vertical Section

VSD: Vertical Section Direction

Az avg: Average Azimuth between 2 points (Az1 + Az2) ÷2

?HD: Delta Horizontal Displacement

In order to get the Positive Vertical Section or Zero Vertical Section, a well path must have difference of angle between VSD and Az avg, (VSD – Az avg), within a range of +90 to -90 degree. On the other hands, the negative Vertical Section can occur because the difference of angle between VSD and A zavg, (VSD – Az avg), is out of range of +90 to -90 degree AZI.

**Ref book: ** **Formulas and Calculations for Drilling, Production and Workover, Second Edition**