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

• Well Seeker will recognise as Inclination-Only any surveys which have the following wording in the name of their IPM file. These names are not case sensitive:

1. INC_ONLY

2. INC-ONLY

3. Inclination Only

4. Inclination-Only

5. Inclination_Only

• Within the Survey Tool Editor (Tools > Survey Tool Editor) there is an option that can be toggled on/off entitled ‘Inclination Only wells display vertical.’

• If ‘Inclination Only wells display vertical’ is turned on and an Inclination-Only IPM has been recognized, the following will happen:

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 plotted and assumed to be completely vertical. No azimuth or inclination values will be used to calculate position data.

3. If an Inclination-Only survey is found with a non-Inclination-Only tool tied on below, the non-Inclination-Only section will be plotted so that it is tied on to the end of the vertical Inclination-Only section.

• Turning OFF ‘Inclination Only wells display vertical’ will stop all the above behaviour and Inclination-Only wells will plot using the inclination and azimuth data provided in the survey grid.

• The default value for the ‘Inclination Only wells display vertical’ option is ON, so by default any Inclination-Only surveys will be treated as above.

• This value is saved within the setup file, so if the user turns this option OFF, Well Seeker will remember this choice.

• 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.