The Friction Wizard (new in release 6.5) is used to determine what friction coefficient(s) give the best match between modeling predictions and observed data. It is used either during the job in real-time, or during post-job analysis. Knowing the best friction coefficients for a well often helps in the job planning of offset wells with similar properties.

Prior to the Friction Wizard, it was necessary to find the best match by a process of trial-and-error, starting with the default coefficients (which are close to the “correct” values in most cases), generating a graph of surface weight vs depth to compare the predictions with the observed data, and then editing the friction coefficients and repeating the process to obtain a better match. The Friction Wizard automates this process.

The first step in the Wizard is to choose between matching a single data point (for example, noted manually during the job) and multiple data points (such as might be obtained from a data acquisition log).

If you want to match a single data point, you need to specify the depth, surface weight, wellhead pressure and (for pipe operations) pump or circulating pressure, as well as the direction of movement. The calculation “rules” allow you to control how the apparent friction coefficient will be calculated – by varying the coefficients equally throughout the well, or just at the local depth.

The Wizard then calculates the Apparent Friction (the coefficient which forces the prediction to match the observed reading) for this single data point. You can then view the Surface Weight graph for all depths and compare the match using the original and newly calculated values of friction coefficient. You may then exit the Wizard, either restoring the original coefficient(s) or switching to use the new one.

Multiple Data Point Calculations

First, the data must be loaded (if it has not already been elsewhere in Orpheus). You can load from either a text-based (ASCII) file or from CTES’ Orion data acquisition. If pressure data is included in the log, you can use it in the modeling. If not, then you must specify a single fixed value which will be used throughout, as shown in the example below.

Data Handling Options allows you to filter the data to a much smaller size, speeding the calculations. Data is typically averaged over 100ft (30m) lengths. You can also disregard data in the near-vertical section of the well, since this will not contribute to the drag and hence friction calculations.

Once the data is loaded, you can choose to either calculate the best friction coefficients for the whole well using the Optimize All button, or calculate each section of the well independently.

The original values for the friction coefficients are shown in blue and the apparent (calculated) values in red. A popup menu allows you to change the project coefficients either collectively or individually. You can also view the calculation details for each well section, to see how many data points were used and how many were rejected for any reason.

The following graph shows some field data plotted on the surface weight graph using the default friction coefficients…

… while this graph shows the same data using the apparent friction coefficients…