Getting results is made easy in Cerberus by the Question & Answer Wizard. The main calculation tasks are presented as questions, and you simply click on the one you are interested in. The symbols on the left indicate the type of result or calculation you will see, for example a numerical result, a graph or a calculation wizard. The questions are divided into four logical sections, as shown below. [Note that some of the questions are different for wireline and coiled tubing, click on the links to see those versions]

• Selecting the BHA

• Getting into and out of the well

• Performing the job at depth

• Other calculations

What size BHA will be able to navigate the bends in the well? - this invokes the Toolfit Wizard, which will tell you what tool dimensions (length and diameter) will fit in a given well size and dogleg severity. If it is necessary to bend the toolstring to get around the corner, the Wizard will tell you how much force is needed.

GETTING INTO AND OUT OF THE WELL

Can I reach the target depth and return to surface safely? - can you reach the target depth without the pipe and then return to surface without exceeding the yield strength. This issue is not as critical for large pipe as it is for wireline or coiled tuibng, but it can still be relevant in some situations. Example

Plot a graph of surface weight against depth - this essential graph shows you what the surface weight readings should be while running into and out of the well. Print this graph for comparison with actual measurements. The same graph displays the pipe breaking strength, and hence what your available overpull is at each depth if you should get stuck. Example

Plot a graph of maximum set-down force (WOB) against depth - how much force can you set down at the end of the toolstring (by slacking off at surface) for each depth. This is extremely important for drilling, as it tells you the maximum weight on bit. Example

Plot a graph of maximum pick-up force against depth - this very important graph shows you how much pull you can apply at the end of the toolstring for each depth before you break the pipe. Example

Plot a graph of stretch against depth - the program calculates what the stretch is at each depth, and hence the “true” depth. It takes into account the shape of the well and how the stretch is distributed by the curvature, unlike conventional stretch charts which are very unreliable in deviated wells. Example

If the production tubing is buckled, will I be able to pull out? - buckled, or corkscrewed, production tubing can present a major problem for thru-tubing operations. Going into such tubing may pose no difficulty, but as soon as you reverse direction and try to come out, the pipe pulls against the helical tubing and the greatly increased drag may make it impossible to pull out without exceeding the breaking strength. This Wizard enables you to estimate the degree of buckling, and then superimpose this profile on the well geometry when performing the regular calculations. This feature is unique to Cerberus. Example

PERFORMING THE JOB AT DEPTH

How much does the set-down force (WOB) vary with weight? - this is a very important result, especially for drilling applications, showing how the WOB varies with surface weight. This can also be used in real-time for predicting WOB at the rig floor without needing downhole tools.

How much pull can I apply at this depth? - the program calculates the maximum pull, and the corresponding surface weight.

How much stretch will I have at this depth? - the program calculates the stretch at each depth, which can be used to correct your measured depth at the wellsite.

What are the forces acting of the pipe and BHA at this depth? - this feature gives a detailed break-down of the component forces which are contributing to the net situation and can be particularly useful when trying to understand complex cases.

Plot a graph of pipe tension vs depth - this is one of a family of graphs which display the conditions along the pipe with the BHA fixed at a particular depth. The other graphs include hydrostatic pressure and wall contact force.

View a 3D animation of pipe tension vs depth - this diagram shows the status (tension/compression /yield) of the BHA and pipe relative to the well geometry. You can animate the diagram in order to view how the status changes with depth. This is particularly useful when demonstrating a difficult point to a client.

Where is the neutral point? - this Wizard calculates where the neutral point is for a given surface weight, and also tells you what the surface weight would need to be in order to place the neutral point at a particular depth, as would be the case for a back-off operation.

OTHER CALCULATIONS

Use the Report Wizard to generate a full analysis and print a report - this Wizard allows you to perform all the key calculations and print a summary in one step, rather than do each one separately. This task is usually done last, after a detailed analysis has been completed manually.

Run a sensitivity analysis of key parameters - this task is extremely important, in order to assess whether the job is marginal or straightforward. Running the project for only one set of input parameters runs the risk that slightly different conditions encountered during the job may produce a different result. The user should test the robustness of the results by trying a range of parameters. The Analysis Wizard automates this task. Example

The pipe is stuck. Perform a pull test and estimate the stuck depth - the Stuck Point Wizard allows you to perform a pull test to determine where the pipe or BHA is stuck downhole. This calculation is relatively simple in a vertical well, but in deviated conditions only this program can account for all the downhole forces when answering this question. Example

If the well continued on the same trajectory, how much further could I go? - results may indicate that you can do the required job at the current depth, but if the well were to be extended a little further would this change matters? This is particularly useful for operators who are considering re-entry and well deepenings. Also, this result is a qualitative indicator of the difficulty of the present job - if a hypothetically deeper well can be entered successfully, the current well will most likely pose few problems. Example

What is the risk of differential sticking? - this Wizard allows you to specify downhole conditions which can potentially lead to differential sticking, and then estimate the effect of this sticking on the surface weight and the ability to pull hard enough to get free should it occur. Example

Find the friction coefficients which give the best match to observed data - this Wizard automates the task of finding what the friction coefficients should be to match measured data to model predictions. Previously, this involved a trial-and-error approach of manually changing the friction coefficients and generating the surface weight graph, noting the offset and going through the process again with slightly modified coefficients until a match is obtained. Example