Calculation modes

Softdrill NL   

 

One of three calculation modes can be selected in the Settings & Parameters tab on the input screen:

 

Single Depth Mode

 

The Single Depth mode calculates tension and torque along the drill string for a specific depth.  Typically this would be the depth at the anticipated end depth of a BHA run but any depth may be chosen.

 

When the model is calculated, the program calculates the tension, torque and normal force values for each of the 5 operational modes. The calculation results are displayed in the Result graph and in the Result data tabs. On completion of the calculation the program will display the Result graph.

 

Single depth tension graph

Initially, the Tension chart is shown.  This graph displays tension along the drill string against measured depth.  Through the chart menu, the chart may be changed to display torque or normal forces. In addition to the drill string tension, the sinusoidal and helical buckling curves as well as the tension limit line are shown.  The blue and green (dotted) lines represent the hole sections and drill string sections.  These are treated as "virtual" charts series so that color, line thickness, etc. can also be adjusted.

Inclination and DLS graph

This chart plots the inclination and dogleg severity (DLS) against measured depth.  In this case both the input survey data (well plan) and simulated survey data (random tortuosity) are shown.

 

Trip Log Mode

 

The trip log mode calculates the surface tension (or torque) against bit depth.  In other words, the single depth model is calculated against a decreasing measured depth, starting at bit depth. At each step the surface tension (or torque) is stored and plotted on the chart.

 

Trip log indicated weight graph

This chart displays the surface tension (or torque) against measured depth.  For each measured depth (defined by bit depth and step length) surface tension is calculated and plotted.  This plot only displays hole sections in addition to the tension (torque) lines.  Drill string sections, buckling and tension (torque) limits lines are not shown as they are not applicable to a continuously changing drill string with progressing depth.

Inclination and DLS graph

This chart plots the inclination and dogleg severity (DLS) against measured depth.  In this case both the input survey data (well plan) and simulated survey data (random tortuosity) are shown.

 

Friction Factor Mode

 

This mode is essentially the same as the Single Depth Mode above but it allows calculating a target surface tension (within a specified range) by varying the friction factor of a selected hole section.  When calculating the model, the following dialog box is presented:

 

Select hole section

Select the hole section for which to calculate the friction factor.

 

Target operational mode

Select the operational mode for which the target surface tension applies.

 

Target surface tension

The target surface tension.  The friction factor for the selected hole section is varied until the resulting surface tension (single depth) is within the specified margin.

 

Acceptable margin

The acceptable margin for the calculated surface tension.  The friction factor is varied until the calculated surface tension is within this margin (target tension tension margin).

 

 


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