Directional survey data

 

Petra uses directional survey data to compute the positions of deviated and horizontal wells for mapping, cross-sections, and calculations. Survey data from a directional drilling company usually consists of some combination of measured depth (MD), inclination (INC), azimuth (AZI) true vertical depth (TVD), North-South offset footage (NS) and East-West offset footage (EW).  

To access a well’s survey data, select the “Dir Survey” button on the Location tab in the Main module. 

General tab

Shows the units for both depths and XY offsets

Data tab

Shows the actual survey points stored in Petra’s database in a spreadsheet format

Preview

Displays projections of the wellbore’s path in three different planes: EW vs. depth, NS vs. depth, and a map view.

Import/Export

Moves survey data into and out of Petra’s database.

Calc TVD tab

Computes the wellbore’s path from a user-specified “kick-off” point

Method tab

Defines which algorithm is used when converting inclination-azimuth data to x-y offsets during import.

Advanced tab

Sets a couple of options for correcting for the convergence angle and for reducing the number of survey data points.

Maintenance tab

Changes directional well flags for all wells selected in the Main module.

Data conventions

The convention for inclination is 0 degrees for vertical and 90 degrees for flat.  Inclinations above 90 degrees are inclined up.  As an example, an 86 degree inclination is going down through section at 4 degrees below horizontal, and a 94 degree inclination is going up through TVD at 4 degrees above horizontal.

Azimuth data is commonly measured in positive degrees measured clockwise from north, where 0 degrees is north, 90 is east, 180 is south, and 270 is west.  This convention is sometimes called “unformatted.”  Less commonly, azimuth data consists of a numeric compass heading in degrees preceded by either the letter N or S and followed by the letter E or W.  As an example, N30E means 30 degrees east of north. S60W means 60 degrees west of south.   This convention is sometimes called “formatted.”  Petra can import and display azimuth data in either convention.

The convention for NS offsets is north offsets are positive and south offsets are negative.  Similarly, east offsets are positive, and west offsets are negative.  

Working with multiple directional surveys

Petra can store any number of survey data sets (both real and planned) for any well. Multiple directional surveys are really intended only for proposed and actual surveys. It’s best to keep each actual completion (even those from the same surface location) separate and in different wells in Petra.  Keeping multiple drilled laterals in the same well greatly limits your ability to display in cross-section, map, and grid as well as store any useful header info or petro physical data.  The multiple survey toolbar is available on the bottom of every tab on the Directional Survey Data window.

Main_SurveyDefMaint

Survey Def Maintenance - This button opens the Survey Def Maintenance tool, which changes how Petra labels different sets of surveys.