Input tab - Settings & Parameters

Softdrill NL   

 

The Input tab is divided into three sub-tabs: Settings & Parameters, Hole Sections & Drillstring and Survey Data. 

The Settings & Parameters tab is for input of general calculation settings and parameters of the individual operational modes:

 

Calculation mode

This field determines the calculation mode.  There are three modes of calculation:

 

1.Single depth

2.Trip log

3.Friction factor

 

Helical buckling

Determines the equation used for calculating the helical buckling force.

 

Stiff string

When this option is selected (checked), the calculation will be performed according to the stiff string model

 

Bit depth

This field determines the length of the drill string.  This may be adjusted as required to evaluate the Torque & Drag model (e.g. surface tension and torque, buckling) at various depth.  If the Bit Depth input is deeper than the last hole section, the depth of this hole section will be adjusted and the user will be warned accordingly when the model is calculated.

 

In the context of a Torque & Drag calculation, all depths are from rotary table.

 

Step length

The Torque & Drag model is a cumulative calculation from the bottom (e.g. bit) upwards.  For this the string is divided into sections (finite elements) and for each section drag and torque are calculated.  These values are then added to the cumulative tension & torque at that depth to finally arrive at a cumulative tension and drag at surface.  The Step length determines the length of each section (i.e. the number of sections into which the drill string is divided).  Changing this value from the default (30m or 100ft) will have a limited (small) effect on the result of the calculation, but will determine how calculated normal forces should be interpreted.

 

Mud weight

Enter the mud weight in use.

 

Safety factor

The safety factor applied to tensile and torsional limitation of the pipe.  Please refer to Safety Factor and Margin of Overpull for more details.

 

Margin of overpull

The margin of overpull applied to the tensile limited of the pipe.  Please refer to Safety Factor and Margin of Overpull for more details.

 

Include block weight

Include the weight of the traveling block and top drive in the calculation.  Note that the block weight is only partially included in the single depth calculation mode.  The plotted chart for the single depth mode can only show tension in the drill string.  As such, the cumulative value at surface (MD = 0) is excluding the block weight.  However, if the block weight is defined and "applied" the surface tension summary on the printed report will also show surface tensions including block weight (i.e. indicated weight).

 

Block weight

The weight of the traveling block (and top drive, if applicable).

 

Number of lines

Number of lines through the block to the draw works.

 

Efficiency

Efficiency of the sheaves.  The default is 98%.

 

Dead line sheave

Type of dead line sheave.  The dead line is the fixed part of the drill line between the dead man anchor and the first sheave (dead line sheave) in the crown block.  If this sheave is rotating it is Active, otherwise it is Inactive.

 

Parameters

Parameters for the individual Operational Modes.  Values not applicable to a particular mode (e.g. WOB for rotating off bottom) are grayed out.  Whilst these parameters should be self-explanatory, it should be noted that BHA Drag and BHA Torque are correction factors.  In principle, BHA drag and torque is calculated from the drill string elements.  If it is suspected that the BHA composition generates additional drag or torque, a value may input in the relevant cell(s) to compensate and adjust the model.  In practice this will be empirical; first the model is calculated with zero values and then adjusted until the model matches actual data within an acceptable margin.

 


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