Dogleg severity (DLS) is a normalized estimation, normally described in degrees per 100 feet or degree per 30 meters, of the overall well bore curvature between two consecutive directional surveys. Regarding a planned well path, dogleg severity may be synonymous about build and/or turn. The following formula provides dogleg severity in degrees/100 ft based on the Radius of Curvature Method.
Dogleg severity (DLS) = {cos-1 [(cos I1 x cos I2) + (sin I1 x sin I2) x cos (Az2 - Az1)]} x (100 ÷ MD)
Where;
DLS = dogleg severity in degrees/l00 ft
MD = Measured Depth between survey points in ft
I1 = Inclination (angle) at upper survey in degrees
I2 = Inclination (angle) at lower in degrees
Az1= Azimuth direction at upper survey
Az2 = Azimuth direction at lower survey
Example for dogleg severity based on Radius of Curvature Method
Survey 1
Depth = 7500 ft
Inclination = 45 degree (I1)
Azimuth = 130degree (Az1)
Survey 2
Depth = 7595 ft
Inclination = 52 degree (I2)
Azimuth = 139 degree (Az2)
Dogleg severity (DLS) = {cos-1 [(cos 45 x cos 52) + (sin 45 x sin 52) x cos (139 - 130)]} x (100 ÷ 95)
Dogleg severity (DLS) = 10.22 degree/100 ft
Please find the Excel sheet used to calculate dogleg severity based on Radius of Curvature Method.
Ref book: 
Formulas and Calculations for Drilling, Production and Workover, Second Edition
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September 20th, 2009 at 10:18 am
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June 8th, 2010 at 11:28 am
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