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Drilling Office

Drilling Office. Close Approach. Close Approach (Cont’). Standard Proximity Calculations Normal Plane : MD interval is recommended because in horizontal wells, TVD interval may have several positions within the object well, creating discontinuous results. Close Approach (Cont’).

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Drilling Office

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  1. Drilling Office Close Approach

  2. Close Approach (Cont’) • Standard Proximity Calculations • Normal Plane: MD interval is recommended because in horizontal wells, TVD interval may have several positions within the object well, creating discontinuous results.

  3. Close Approach (Cont’)

  4. Close Approach (Cont’) • Standard Proximity Calculations • Horizontal Plane: TVD interval is recommended because in highly deviated wells (with inclinations at or exceeding 90°) it is possible to have multiple penetrations with the horizontal plane and multiple distances from the same point in the subject well

  5. Close Approach (Cont’)

  6. Close Approach (Cont’) • Standard Proximity Calculations • 3D Least Distance: (Reverse Normal Plane) Computes the radius of a sphere centered on the subject survey that just touches the offset survey.

  7. Close Approach (Cont’)

  8. Close Approach (Cont’) • CALCULATION OUTPUTS • center-to-center distance • ellipse of uncertainty (EOU) distance • separation factor • alert radii

  9. Close Approach (Cont’) • center-to-center distance • The straight-line distance between the subject survey and an offset survey • No error analysis is incorporated in this calculation.

  10. Close Approach (Cont’) • ellipse of uncertainty (EOU) distance • The ellipse of uncertainty (EOU) distance is equal to the ct-ct distance minus the sum of the ellipse semimajor axes of the subject well survey and the offset well intersection point survey.

  11. Close Approach (Cont’) • separation factor • Separation factor = (ct – ct distance)/(Sum of EOU semimajor axes) • S.F. > 1, the error ellipses do not overlap • S.F. = 1, the error ellipses just touch • S.F. < 1, the error ellipses overlap

  12. Close Approach (Cont’) • alert radii • Major Risk • The major risk radii are defined as the smallest cones of the three available alert zones. The major risk zone specifies close approaches that come so close to the nearby well that a dangerous situation exists, even if the offset well is shut in.

  13. Close Approach (Cont’) • alert radii • Minor Risk • The minor risk radii are defined as a warning zone, so that any wells coming within the warning zone can be shut in; however, these wells are not as critical as a well entering the major risk radii.

  14. Close Approach (Cont’) • alert radii • Drilling Buffer • The drilling buffer radii is a zone defined to ensure enough clearance from nearby wells to allow for normal deviation from a plan during drilling operations. This buffer ensures efficiency in the drilling operation, without adding any unnecessary expenses for anticollision purposes.

  15. Close Approach (Cont’) • alert radii • The alert radii are defined by an initial radius at the surface, and a table of user-defined, growth rate information. The growth rate information defines the TVD range for a cone. The cone has an initial radius that is equal to the parameter set at the surface and grows at the user-defined rate, down to the specified depth. The next TVD range starts where the previous range left off and grows according to next level of user-defined specifications. The zone sizes can be set by the user and are generally defined by the operator’s anti-collision policies or rules.

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