Dogleg Severity Calculator
Calculate dogleg severity (DLS), build rate, turn rate, and toolface angle using the minimum curvature method.
Survey Station Inputs
DLS = (100/ΔMD) × arccos[cos(ΔI) − sinI1×sinI2×(1−cos(ΔA))]
Results
Dogleg Severity
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Overall Angle Change
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Build Rate
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Turn Rate
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Toolface Angle
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Ratio Factor (RF)
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ΔTVD
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ΔDeparture
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How this was calculated
Method: Minimum curvature (API standard). The wellpath between two survey stations is modeled as a circular arc.
Dogleg angle: cos(DL) = cos(I2-I1) - sin(I1)*sin(I2)*(1-cos(A2-A1))
Ratio factor: RF = (2/DL)*tan(DL/2). When DL is near zero, RF approaches 1.
Build rate: Rate of inclination change per 100 ft = 100*(I2-I1)/deltaMD
Turn rate: Rate of azimuth change per 100 ft = 100*(A2-A1)/deltaMD
Guidelines: DLS below 3 deg/100ft is mild. 3-8 deg/100ft is moderate. Above 8 deg/100ft may cause drill string fatigue and casing wear issues.
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Book a free strategy call →Understanding Dogleg Severity in Directional Drilling
Dogleg severity (DLS) measures the rate of change of the wellbore trajectory, expressed in degrees per 100 feet (or per 30 meters). It captures the combined effect of inclination change (build/drop) and azimuth change (turn) between two survey stations. High dogleg severity creates problems: increased casing wear, drill string fatigue, key-seating, difficulty running casing, and poor cement jobs.
The minimum curvature method is the industry-standard API calculation for directional surveys. It models the wellpath between two stations as a smooth circular arc rather than straight tangent lines. The ratio factor (RF) adjusts for the curvature when computing incremental TVD, northing, and easting coordinates. This method provides the most accurate representation of the wellpath among the common survey calculation techniques.
As a general guideline, DLS below 3 deg/100ft is considered mild and poses minimal risk. Between 3-8 deg/100ft is moderate and requires careful BHA design. Above 8 deg/100ft is severe and may necessitate special considerations for drill string design, casing running procedures, and completion equipment selection.
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