Input tab - Hole sections & Drill string

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The second sub-tab of the Input tab contains the hole sections and drill string input.


Hole sections

The hole sections define the geometry of the borehole.  The following fields must be entered:


1.MD Bottom: The bottom depth (along the borehole) of the hole section.  Using the bottom depths, MD Top for each hole section will be calculated with the first section starting at 0.00.

2.Section type: Select one of the following types from the drop-down list: Casing, Liner, Open hole.  The value selected here, determines whether data lookup is available.  For Casing or Liner, the ellipses button [...] may be clicked in the Hole Size column to select the casing (liner) ID from the catalog and fill in the Hole Size cell.

3.Hole Size: The diameter of the open hole or ID of the casing/liner.

4.Friction factor: Dimensionless number used to calculate torque & drag.  For details, please refer to Friction Factors.


Hole sections should be input to reflect the exposure to the drill string only.  For example:


In case a casing string consists of casing with different ID's, the Hole Section may be split.  For example, if the bottom part of a casing string has a smaller ID (greater wall thickness) than the top part, simply create two hole sections.  The first section will then have the Hole Size set to its ID and its MD Bottom will be equal to the top depth of the casing on the bottom of the string.

It is also possible to simulate open hole sections with different friction factors (some formations may yield more friction). Simply create three (open) hole sections.  For example, in the hole sections below a higher friction factor (0.40) is defined for the open hole section between 2400 and 2600m MD.  Above and below, a friction factor of 0.30 is defined.



Drill string

The drill string must be entered from the bottom up (i.e. from the bit upwards).


1.Type: Defines the type of tool.  Multiple options are available and each option is internally mapped to a relevant lookup tool type.  Lookup (from the catalog) is accessed through the ellipses button [...] in the Description field.  For example: if the Type field is set to 'Stabilizer', the lookup catalog for 'Drill collar' is shown when the ellipses button is clicked.  Note that for some Types, lookup is not available (e.g. Bits).

2.Description:  The Description may be freely entered as required.  If a selection is made from the lookup dialog, the Description will be completed from the lookup data if the Description field is still blank.  If the Description field already contains a value, the option will be given to leave the Description as it is or to overwrite it.

3.OD: The primary OD of the tool.  For example for drill pipe this must be the pipe body OD (not the tool joint OD) and for a stabilizer it must be the fish neck (body) OD and not the stabilizer gauge OD.

4.Torque OD: The maximum OD of the tool.  For example for drill pipe this must be the tool joint OD (not the pipe body OD) and for a stabilizer this must be the stabilizer gauge OD and not the fish neck (body) OD.  It is not possible to enter a Torque OD smaller than the tool OD; the program will automatically correct smaller values to the tool OD value.

5.ID: The internal diameter of the tool.  For tools that have no specific ID (e.g. mud motors, MWD's) an equivalent ID may be entered.  Based on a relative stiffness of the tool, this can be calculated using the Moment of Inertia.

6.Length: The total length of the tool or group of tools. Tools of the same type and specification may be grouped as a single tool (e.g. drill collars, drill pipe).

7.Nom. Wt.: Nominal Weight of the tool.  For drill pipe this will be different from the actual weight. Note that this field is provided for reference only; it is not used in calculations. For clarity: this weight is entered per meter of per foot, not the total weight of the tool.

8.Act. Wt.: The Actual Weight (corrected weight) of the tool. Primarily applicable for drill pipe (i.e. including tool joints).  Other tool weights may be manually corrected by dividing the total tool weight by the length of the tool.

9.Tension limit: Maximum tension that may be applied on the tool.  Typically this value is automatically entered from the lookup dialog but is may also be calculated manually by multiplying the material tensile strength (e.g. pounds per square inch) with the cross-sectional area of the pipe.

10.Torsion limit: The maximum torque that may be applied on the tool.

11.Make-up torque: The maximum recommended make-up torque for the tool's connections. If this value is  lower than the Torsion limit (normally the case), it is used in calculating the maximum allowable torque for the drill string.

Tension limit, Torsion limit and Make-up torque must be entered at 100%. They will be corrected in the calculation with the Safety Factor and Margin of Overpull specified in the Setting & Parameters tab.  Applying  a safety factor to these values will cause the values to be too low and the calculation result to be too conservative!

There is no need to input individual drill string elements for tools that have the same OD and ID; these may grouped together.  For example a BHA may be simplified as shown below.  Note that if one or more of the stabilizers has a different gauge, the BHA still can be simplified but should be split in sections with similar torque OD.



Move up button

Select a tool record and click this button to move it up by one position in data grid (i.e. down the drill string). If no tool record is selected, or if the top-most tool record is selected, this button is disabled.


Move down button

Select a tool record and click this button to move it down by one position in the data grid (i.e. up the drill string). If no tool record is selected, or if the bottom tool record is selected, this button is disabled.






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