Detection of the stuck point to locate the lowest possible back-off point can be established by stretching the string and using the stretch charts for drillpipe. This method gives only an approximate value for the free point and shall only be used to locate the approximate stuck point for spotting pipe free pills and to provide a starting point for using the Free Point Indicator Tool.

Free Point Indicator Tool

In order to back-off the string at the deepest possible point, a free point indicator tool (FPIT) can be run on electrical wireline. By applying stretch and torque on the pipe, the FPIT can determine elongation or rotation at any depth by use of an independent sensor placed between two mechanically activated anchors. The FPIT shall be the definitive measurement of the location of the stuck point for back-off depth determination.

A plot of depth versus the percentage of surface torque and pull transmitted downhole will show the deepest point at which the string is free.

Guidelines for Running FPIT

Before running the FPIT

Check anchor tips for wear and correct size for the particular size drillpipe in the hole
Note: All ID’s of the string shall already have been checked to ensure that the tool can pass through

Measure the stretch of the pipe to determine the approximate position of the free point

Pull to the neutral weight of the pipe above the stuck point. Mark the pipe at this point and label this point “Mark 1”

Pull to the neutral weight of the pipe plus the stretch required from the wireline contractor’s tables. Label this “Mark 2”

Note 1: From this point on, the weight indicator gauge shall be observed but not used. All tensions are referred to by the marks on the drillpipe

Note 2: It is essential that the pipe is pulled up to the marks to avoid problems concerning the pipe friction in the hole

Running the FPIT

Run the FPIT to approximately 2ft above the estimated free point

Take the stretch measurement first and then the torque measurement

Check the readings to ensure that the FPIT is not slipping and that the torque has been worked down properly

Take additional readings above and below the stuck point in order to build confidence in the final determination of the free point and where to back off the pipe.

Deviated Holes

When taking free point surveys with the wireline FPIT, the Drilling Supervisor shall be in the logging cabin with the logging engineer to study the behaviour of the tension and torque indications and to get a feel for the string reaction to the pull and torque at various depths required to overcome friction.

When surveying for free point in deviated holes:

• always take tension readings first before taking torque readings (this is especially important in deviated holes where residual torque can give false indications that the pipe is free when tension is applied)
• after each torque reading, the pipe shall be rotated a few turns to the left to get rid of any residual torque
• all FPIT readings taken shall be checked against the wireline operator’s nomograph to confirm the meter point readings.