Calculation of Measured Depth in a Build and Hold Trajectory

What's given:

  • Distance to kickoff (D1)
  • TVD of well (D3)
  • Horizontal displacement (H)
  • Degrees per ft , q

What's asked for (most often):

  • Final build angle, theta
  • MD to end of build section
  • MD to target (as given with x,y coordinates H,TVD)


General Procedure:

  1. Calculate r using q (deg/ft)
  2. Calculate angles omega and theta
  3. Calculate incremental MD in build section
  4. Calculate incremental MD in hold section (if required)
  5. Calculate TVD at end of build section


Think about what you are given, a target in terms of H, TVD. Then think about what you don't know, which is all TVD's and MD's from the kickoff point to the target. You should be able to calculate any point in terms of TVD and MD along the well trajectory.


Calculation Procedures (Keep your work organized!):

  1. r=180/pi
  2. Calculate del Y = D3-D1
  3. Calculate del X=H-r
  4. A=r/(del X + del Y)^0.5
  5. omega=asin(A)
  6. B=del X/del Y
  7. theta = omega-atan(B). Finally- the rest is easy!
  8. MD at end of build =D1+ theta/q
  9. MD to target= D1+ theta/q+r/tan(omega)