Well Seeker X: Sidetrack Guide
1.0 – Introduction
The purpose of this document is to help guide the user through the steps required to create a sidetrack.
Depending on the requirements, it is possible to create 3 different types of sidetrack within Well Seeker:
A plan which sidetracks another plan
A plan which sidetracks a survey
A survey which sidetracks another survey
NOTE: It is not possible to create a survey which sidetracks a plan.
The steps required to create the sidetrack are the same, regardless of which of the above 3 options are required.
This document will detail the steps required to create a sidetrack under 2 different conditions:
When the sidetrack and the motherbore both have the same depth reference
When the sidetrack and the motherbore have different depth references
2.0 - Setup
In order to create a sidetrack, the user must first enter a well which will act as the motherbore. The motherbore can be either a plan or a survey. For the purposes of this guide, it will be assumed that the motherbore has already been created in Well Seeker.
2.1 – Depth Reference
Any well plan or survey which is entered in Well Seeker requires a depth reference to be assigned to it. In most cases this will consist of:
A Ground Level Elevation above a System - Usually MSL
A Datum above a System – Usually RTE or RKB above Mean Sea Level
When planning a sidetrack, it is important to know what the depth reference of the motherbore is and what the depth reference of the sidetrack is. There are 2 possible situations which the user may encounter.
The first situation is where the depth reference for the motherbore and sidetrack are the same. As the ground level is unlikely to change, the variable in most cases is the RTE above ground level, so this situation is usually experienced when the sidetrack is drilled with the same rig.
The second situation is where the depth reference for the motherbore and sidetrack are different. This is usually experienced when the sidetrack is drilled with a different rig, where the RTE above ground level is different when compared to the motherbore.
The following two sections detail the steps required to deal with these two situations.
3.0 –Sidetrack & Motherbore with the same depth reference
This section will cover the creation of a sidetrack using the same depth reference as the motherbore.
Firstly, the user needs to open the well properties and ensure that the Motherbore Depth Reference is checked as Default. In this situation it is likely that other than the Default datum on line 1, the motherbore depth reference will be the only other option. Once selected, hit Apply and then Close.
In the Database Tree, right-click on the well containing the motherbore and select one of the following options:
Insert new actual well if the sidetrack is a survey.
Insert planned well if the sidetrack is a plan.
The Plan Properties/Actual Wellbore Properties dialog will appear. Fill in the Properties, Vertical Section and Magnetics Sections as normal
If the motherbore depth reference was correctly selected as default, then this should be referenced in the Depth Reference section. If it was not correctly selected as default, something else will be referenced here and the user will need to select the correct reference from the drop down menu.
If the user needs to do this, a warning box will appear. Choose the option Preserve TVD’s.
In the Sidetrack Details section, check the “Plan is tied to” or “Well is a sidetrack” checkbox, depending on if you are creating a plan or survey.
Select the mother bore from the Parent Well/Plan drop-down box and enter the sidetrack depth in the Sidetrack Depth box. Note that the depth must be within the range of the motherbore i.e. a motherbore with a TD of 1000m MD can’t be sidetracked at 1010m MD etc. Then click on the Create Tie-on / ST box.
As soon as create sidetrack has been selected, the below warning will appear. This is warning that proceeding will reset the survey program in the plan or actual wellbore properties. This is not an issue as this section will currently be blank anyway. Select Yes.
The Survey Program and Tie-On sections will automatically update based on the sidetrack depth entered. The survey program will now mirror the survey program of the motherbore down to the sidetrack point, and the tie-on section will automatically show the details of the tie-on line. Click on Apply and then Close to close the Plan Properties/Actual Wellbore Properties.
At this stage the process differs, depending on whether the user is creating a planned or actual sidetrack.
3.1 – Planned Sidetrack
When the sidetrack is a plan, all the user needs to do is open the plan by double right clicking on the plan level. This will open the plan and the tie-on line in row 1 will mirror the sidetrack depth entered in the plan properties dialog.
The user can now build their sidetrack plan as per their planning requirements.
3.2 – Actual Wellbore Sidetrack
When the sidetrack is an actual wellbore, the first thing the user needs to do after selecting the ST depth and closing the Actual Wellbore properties (Section 3.0) is to create a new survey. The actual wellbore will already contain the motherbore surveys from surface to the ST depth, but in order to enter the ST surveys, the user must first create a new survey.
To do this the user should right click on the actual wellbore and select Insert New Survey.
In the survey Properties Dialog, select From Survey in the tie-on section and from the drop-down section, select the survey that you want to sidetrack. Note that when the appropriate survey has been selected the MD cell will be populated with the deepest survey station for the selected survey. If required, the user can then manually overwrite this value with the appropriate ST depth.
The user can then select the appropriate Survey Instrument from the drop-down menu and select Apply and then Close.
The user can now double right click on the newly created survey. This will open the survey and the tie-on line in row 1 will mirror the tie-on depth entered in the survey properties dialog.
The user can now enter the appropriate surveys as they are received.
4.0 –Sidetrack & Motherbore with different depth references
This section will cover the creation of a sidetrack which has a different depth reference to the mother bore. This can happen, for example, when a well has been previously drilled with one rig and then sidetracked with a different rig.
In the Database Tree, right-click on the well containing the motherbore. Select Properties to open the Well Properties dialog.
In the Depth Reference section, create a new depth reference in the line below the motherbore reference. Give your depth reference a name in the Datum Name column. In the Elev above system column, enter the depth reference height of the sidetrack. Enter the name of the rig used to drill the sidetrack (if available) in the Rig column. Enter the ground level elevation in the Ground Elevation to MSL box. At this stage it is important to check that the Air Gap has been calculated correctly. If this value is not correct, then an error has been made entering the data and this needs to be addressed.
In the above you can see that the RTE above ground level for Rig 2 is 5m greater than Rig 1. Once the user is happy the new elevation has been entered correctly it is important to then select the new ST datum as the Default. Selecting the new ST datum as default at this stage will save a lot of unnecessary steps during the rest of the process which can lead to mistakes being made, so this is an important selection to make. Click on Apply and then Close to close the Well Properties dialog.
In the Database Tree, right-click on the well containing the motherbore and select one of the following options:
Insert new actual well if the sidetrack is a survey. Note, you can only sidetrack an existing survey with this option. If the motherbore is a plan, then this can only be sidetracked by another plan.
Insert planned well if the sidetrack is a plan.
The Plan Properties/Actual Wellbore Properties dialog will appear. Fill in the Properties, Vertical Section and Magnetics Sections as normal. Check to make sure the depth reference is correct. If the new ST datum was selected as default in the Well Properties dialog, then this should be correct.
In the Sidetrack Details section, check the Plan (or well) is a sidetrack checkbox.
Select the motherbore from the Parent Well/Plan drop-down box. This is now the point where the user should select the appropriate sidetrack depth. The sidetrack depth entered in the cell will be referenced to the Depth Datum selected in the plan properties dialog, which may differ from the motherbore. In the situation where the datum selected is different from the motherbore, the user needs to be very careful at this point to ensure they enter the correct depth.
Referencing the below diagram, if the user needs to sidetrack the motherbore at 1000m MD, then they should enter the sidetrack depth as 1005m MD.
Note that the depth must be within the range of the motherbore i.e. a motherbore with a TD of 1000m MD can’t be sidetracked at 1010m MD etc. Then click on the Create sidetrack box.
As soon as create sidetrack has been selected, the below warning will appear. This is warning that proceeding will reset the survey program in the plan or actual wellbore properties. This is not an issue as this section will currently be blank anyway. Select Yes.
The Survey Program and Tie-On sections will automatically update based on the sidetrack depth entered. The survey program will now mirror the survey program of the motherbore down to the sidetrack point, and the tie-on section will show the details of the tie-on line. Click on Apply and then Close to close the Plan Properties/Actual Wellbore Properties.
At this stage the process differs, depending on whether the user is creating a planned or actual sidetrack. For instruction regarding this process, refer to Section 3.1 – Planned Sidetrack and 3.2 – Actual Wellbore Sidetrack.
4.1 – Checking the ST point is correct
As soon as the user has setup a planned or actual sidetrack the first thing they should do is check that the sidetrack point has been chosen correctly. One way to double check this is to compare the ST tie-on line with the interpolated sidetrack point on the motherbore.
In the below screenshot, the motherbore plan is on the left and the interpolate window shows the interpolated sidetrack point on the motherbore at 1000m MD. To the right is the sidetrack tie-on line. When the RTE between the motherbore and ST are different, it is expected that the MD and TVD will be different when comparing these, but if the inclination, azimuth, NS, EW and TVDss are the same, then the ST depth has been chosen correctly. If these values do not tie in, then the user should double check the sidetrack depth selected and adjust appropriately.
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