## Ellipse Of Uncertainty

The concept of an ellipse at any point in a drill hole to quantify the possible locations of the point is illustrated with the following example.

Suppose the measured depth is 2500 feet as shown in the sketch and that systematic errors (errors which regularly re-occur and are not compensating) at any survey station are 1° in azimuth, 0.5° in inclination, and 1 part in 500 for measured depth. Further, suppose the inclination and azimuth are thought to be 30° and 90°, respectively.

EAST

NORTH A MD sin I

EAST

EAST

VERTICAL

The expected location of the bottom of the drill hole is

The actual location of the bottom of the drill hole could be anywhere within a volume shown as an ellipsoid in the sketch. The dimensions of the ellipsoid are given by the variations of variables of inclination, azimuth, and measured depth. The maximum dimensions of the ellipsoid and consequently the position of uncertainty which is called the "ellipse of uncertainty" are

+8 -1

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### Responses

• isengar greenhand
What is the cone of uncertainity in directional drilling?
7 years ago
• Susanne
What is ellipse of uncertainty?
6 years ago
• katja pusila
What is oil and gas well elipsoid?
5 years ago
• ireneo
What is the ellipsoid of uncertainty?
5 years ago
• Vanessa
What is ellipsoid of uncertainty in directional survey?
5 years ago
• pietro romano
Why the ellipsoid of uncertainty is not round?
2 years ago
• aija
Why is directional uncertainty an elipse?
2 years ago
• kate
Why error surface of mwd survey is elliptical?
1 year ago
• HARRIET
What is ellipses of uncertainty?
1 year ago
• anna
Why does ellipse of uncertainty larger when drilling east west?
11 months ago