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ISCWSA Error Model Calculations
04 July 2017
Hi everybody,
I am looking for any example of ISCWSA Error Model calculations. I have input data: N,E, TVD calculated from azimuth inc and md. Now I want to calculate dimensions of elipse using ISCWSA error model. How to calculate error and sum it up  in station and between stations? I have read Introduciton to well positioning but I dont understand some equations(for example what is dr/dp in pg 172 appendix A, do I need it if I have calculated N,E, TVD by my function?).

I am writing master thesis about anticollision and I would be really appreciated if you could help.   .
3 answer(s)
Wellbore Positioning Advisor
Total Posts: 32
Join Date: 03/07/08
If you have not already done so, you should review the Industry Steering Committee on Wellbore Survey Accuracy ( documents found under "docs and publications" tab  and then "Collision Avoidance Sub-Committee".   Especially useful is the document "Current Common Practice in Collision Avoidance Calculations".

I assume you are referring to page 172 in the ISCWSA Education Committee's Joint Industry Project e-book "Introuduction to Wellbore Positioning" V06.02.17:

The error at each station is the error at the previous station added (or Root-Sum-Squared, depending upon propagation mode) to the error between the previous and current station.  Professional wellplanning software such as Compass, Well Architect, HawkEye3D, KellyDown, and others calculate these errors for use in anticollision calculations.  These are not trivial calculations.  The ISCWSA error model committee provides some reference wellpaths with the values calculated to validate the results of different software.  This is a Microsoft Word document with an embededded Excel Workbook with the wellpaths, 1 sigma errors in HLA (Highside, Lateral, Alonghole) form, and calculated clearance factors.

Student, BSc Petroleum and Gas Engineering
Total Posts: 2
Join Date: 04/07/17
I would be very gratefull!
[email protected]
Night Drilling Supv
Total Posts: 3
Join Date: 16/07/16

I am a directional driller and have some documents that may help.

Please provide an email address to send them to.

I tried attaching one file that may help but too large.

Posted by

Grzegorz Orłowicz

Student, BSc Petroleum and Gas Engineering


Total Posts: 2
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