6.3 - Anti Collision
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The Anti-Collision page shows the anti-collision results between the selected well (aka the reference well for anti-collision purposes) and any offset wells assigned to the selected well.
Anti-collision rules can be set at operator level in the Object Explorer. For more information see section 5.1 – Operator Level.
Offsets can be selected in the Anti-Collision edit menu, or in the Surveys page. Click on the icon in the bottom right of the page to open the edit menu, which has the following functions:
The Offset Selector displays the Object Explorer, which contains the selectable wells and plans. Note that wells will only display if they are referenced to a compatible CRS. The levels in the tree can be expanded or collapsed by clicking on the + and – symbols.
Click on the checkbox beside each actual well or plan to select it as an offset. Selecting an object in the object explorer also selects everything in the levels below it. The type of object that is selectable in the tree can be filtered by unchecking the Actual Wells, Plans and Principal Plans checkboxes at the top of the window.
The user can use the search box above the object explorer to search for a specific well. They can also select wells based on distance from the selected well’s wellhead by entering a radius in miles into the Global Scan box in the top right. Click on the Search button to select all wells within the specified radius. Click on the Apply button to apply your selection and close the window.
The bottom half of the page displays the Offsets Grid, which contains a list of all of the assigned offsets for the reference well. Clicking on the checkbox beside each offset will select it, and display it on the anti-collision charts at the top of the page. If no offsets are selected, then all of them are displayed on the charts.
MD, Inc, Azi: The measured depth, inclination and azimuth of the reference well.
Off MD, Off Inc, Off Azi: The measured depth, inclination and azimuth of the offset well.
Off TVD, Off NS, Off EW: The total vertical depth, north/south position and east/west position of the offset well.
Ref Casing, Off Casing: The size of the casing for the reference and offset well. Depending on the anti-collision settings on the operator page, these could be added or subtracted to the ellipse of uncertainty for the wells.
TFO: The bearing of the offset well from the reference well.
Ref Ellipse, Off Ellipse: The size of the semi-major axis in ellipse of uncertainty for the reference and offset wells.
Ellipse Sep: The ellipse separation between the reference and offset wells.
C2C: The distance between the centre of the reference and offset wellbores.
SF: The separation factor between the reference and offset wells.
Warning: If any warnings are violated at the current survey point it will be highlighted here.
The top of the page is split into four charts – the anti-collision summary, travelling cylinder, separation factor plot and ladder plot. Hovering over the left or right hand side the page will display a < or > icon. Clicking on these icons will cycle through the charts.
The four charts are described in the sections below:
The Anti Collision Summary lists all selected offsets and show the depths where the centre-to-centre distance (C2C), ellipse separation (ES) and separation factor (SF) are the smallest. The centre-to-centre distance and separation factor are colour coded to show if they have violated any warning levels.
The Travelling Cylinder is specialised anti-collision plot that shows the relative distance and bearing of offset wells. The centre of the plot is the centre point of the reference well. The selected offset wells will display over the entire depth range of the individual offset wells, unless a depth filter has been applied using the TVD Min/TVD Max options.
The distance of a survey point from the centre of the plot represents the centre-to-centre distance between the reference well and that point. The bearing of a point is referenced to well highside or true north depending on the HS Ref setting.
The plot can be zoomed in and out using the mouse wheel. The Travelling Cylinder plot has some extra options on the left:
HS Ref: When checked, the travelling cylinder will be referenced to the highside of the selected well. The bearing of other wells is measured from the highside of the selected well. When turned off, the travelling cylinder will be referenced to true north. The bearing of other wells is measured from true north.
Depth Labels: Adds a measured depth and TVD value to each survey point.
Well Names: Adds the well name to each offset well.
TVD Min / TVD Max: Allows the user to set a depth filter for the plot. Offset wells will only display survey points with a TVD above the TVD Min value and below the TVD Max Value.
The separation factor plot shows the separation factor vs measured depth for all offset wells for the selected well. The lines running horizontally across the chart represent the warning levels are set in the Operator page. The chart can be zoomed in by scrolling the mouse wheel and moved around by left clicking and dragging. Hovering over a line will display the name of the offset well along with the measured depth and the separation factor at that point.
The ladder plot shows the centre-to-centre distance vs measured depth for all offset wells for the selected well. The red bar under each line represents the size of the ellipse of uncertainty for that well. The chart can be zoomed in by scrolling the mouse wheel and moved around by left clicking and dragging. Hovering over a line will display the name of the offset well along with the measured depth and the centre-to-centre distance at that point.
Refresh: Refreshes all data on the page.
PDF: Prints a PDF format anti-collision report. Note that at least one offset well must be selected in the Offsets Grid in the bottom half of the page.
Hide Charts: Hides the charts at the top of the page so that only the Offsets Grid is visible.
Select Offsets: Opens the Offset Selector, which allows the user to assign or remove offsets for the selected well.
To see a detailed breakdown of the anti-collision results for an offset, click on the icon to expand it. Surveys are highlighted in red if they represent the minimum value for either the centre-to-centre distance (C2C), ellipse separation (ES) or separation factor (SF). For each survey point the Anti-Collision page displays the following information:
