Technical Notes

Daily Operations Report > Survey Section

The results of all daily directional surveys conducted on a Wellbore are recorded, calculated in the Survey section of the Daily Operations report.

Survey Properties establish the permanent data reference for the survey calculations for each survey tool run. Once this information is entered, it should only be changed in special circumstances.

Vertical Section Angle (Azimuth)

The Vertical Section is a straight-line path between a given surface reference point (typically the wellhead) and the primary target or bottom hole location. The Vertical Section Angle is typically the angle of the plane from the Northing Reference (Grid North or True North). Its orientation is measured in degrees from 0 to 359.99.

Since any directional Well’ s trajectory is three-dimensional, the mapping of its progress can be difficult when limited to two dimensions. In order to monitor a Well’ s progress and "map" it graphically in two dimensions, at least two views must be represented: the horizontal plan view and the vertical section view.

The horizontal view ( a.k.a. "plan view") plots the Well’ s trajectory in the horizontal plane. The vertical section view, which is a cross-sectional view usually plotted against a straight line between the wellhead and the primary objective along the Vertical Section Angle.

Can the Vertical Section Angle Change?

Yes, sometimes a Vertical Section Angle (i.e., the reference plane) changes during the progression of the Well; especially when the objectives are multiple targets in different planes. This is very common in a multi-target, 3-D Well where several different vertical sections are plotted depending on the current status of the Well relative to the intermediate targets at any given time. OpenWells, however, does not support this. Multiple Vertical Section Angle (Azimuth) can only be managed in the COMPASS™ application.

Spreadsheet Entries: Calculated Parameters

The Survey Editor calculates the following fields:

V. Sec (Vertical Section)

Vertical Section is calculated using the following equations:

• Closure Azimuth = ArcTAN [ ]

• Azimuth Difference = Closure Azimuth - Vertical Section Azimuth

• Closure Distance = √ Y² + X²  (i.e. The length of the hypotenuse of a right angled triangle, with two sides of length x and y (square root of x2 + y2). Where Y = N/S coord & X = E/W coord.)

• Vertical Section = Closure Distance x COS (Azimuth Difference)

As you can see from the equations above, if there is no vertical section offset, the vertical section calculations are much more simplified (subtraction of the offsets is not required in the closure calculations).

DLeg (Dog-Leg Severity)

Dog-Leg Severity between two survey stations (1,2) is calculated using the following method:

• DL Angle = ArcCOS [ COS(Inc1) x COS(Inc2) + SIN(Inc1) x SIN(Inc2) x COS(Azm2 - Azm1)]

• DLS = (DL Angle x DLS Factor) / (MD2 - MD1)

Where the DLS Factor is the length of the "normalized DL" (i.e., the DLS interval). When using API units, this is usually set to 100 feet and when using SI is 30 meters and sometimes 10 meters. The actual values used for "DLS Factor" are configured by your System Administrator.

Build

Build or Build-up Rate Curvature in the vertical plane is calculated as:

• Build = (Inc2 - Inc1) / (MD2 - MD1)