Inclination Only IPM Guidelines

Details the different ways the user can configure Well Seeker Pro to handle Inclination-Only MWD error models

Well Seeker Version 2.2.1.5 and later has changed the way that Well Seeker Pro manages Inclination-Only instrument performance models (IPMs). The following guidelines clarify how the user should configure Well Seeker for use with Inclination-Only IPMs:

1) Inclination-Only Models

Well Seeker will recognise a survey tool as Inclination-Only if it has the following wording in the name of their IPM file. These names are not case sensitive, but anything other than the below will not be recognised as inclination only:

1. INC_ONLY

2. INC-ONLY

3. Inclination Only

4. Inclination-Only

5. Inclination_Only

2) Changing IPM File Name

IPM file names can be edited by opening the Survey Tool Editor (Tools >> Survey Tool Editor) and selecting the Open IPM Folder option in the toolbar. This will open a Windows folder where the file names can be edited.

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3) Inclination-Only Survey Behavior

If a survey has been assigned an Inclination-Only survey tool, the following behavior will occur:

1. The inclination values in the survey will be used to calculate the Ellipse of Uncertainty (EOU) in the error model.

2. The well will be treated as if it were completely vertical. No azimuth or inclination values will be used to calculate North/South, East/West, Vertical Section, Dogleg, Build Rate or Turn Rate i.e. they will all be zero.

3. However, the TVD and TVD Subsea values will be calculated using the inclination values. A constant azimuth value is assumed for the purpose of the calculation.

4. If an Inclination-Only survey is tied onto a non-Inclination-Only only survey, or vice versa, the non-Inclination-Only surveys will plot as normal but all Inclination-Only surveys will plot as vertical.

4) Inclination-Only Sensitivity to Zero Inclination Surveys

It should be noted that when using an inclination only IPM, the difference in the calculated error ellipse for a portion of a well with a zero degree inclination, when compared to a portion of a well with a positive inclination (0.01 degrees or greater) can be very large. This is caused in a large part by the misalignment term XYM1 in the inclination only models that has a very large magnitude and is based upon the sine of the inclination.

When inputting surveys for a well that is using an inclination only IPM, ensure that the surveys are input as per the inclination only survey results. Inputting an inclination of zero, where in reality it is not, will have a huge impact on the calculated error ellipse.

5) Prior Versions of Well Seeker Pro

Note that in versions prior to 2.2.1.5, the user had the option to toggle Inclination-Only behaviour on and off in the Survey Tool editor. This option has been removed, and Inclination-Only behaviour is now always on. If the user wishes to stop Inclination-Only behaviour in a survey, they must switch to a non-Inclination-Only survey tool, or rename their Inclination-Only IPM in a way which does not correspond with the naming convention described earlier in this document.