Overcoming Challenging Openhole Conditions Using Flotation Approach
Authors: Al Haji Ahmed , Zholaushiyev Makhanbet , Neldybayev Alibek 
Published: February 2023

This paper summarizes the use of an interventionless flotation device when deploying casing, liner or completion strings to increase the success rate of reaching the planned target depth (TD). This can be challenging, especially in wells with extended lateral lengths (ERD) and high angled dogleg well profiles. High frictional forces can pose difficulties running different tubular configurations throughout the horizontal open-hole (OH) section to well TD. Sometimes these additional side forces and friction can prevent deployed tubular configurations from reaching target depth.

Flotation devices are deployed as part of the completion configuration, whether casing or a liner, and they allow air to be trapped in a portion of the installed completion. The trapped air increases the buoyancy of the completion string, reducing the frictional forces along the wellbore in the process. Also, some drilling fluid is filled inside the casing and above the tempered-glass flotation device to provide additional forces to push the completion string to TD. At well TD, pressure is applied from surface, shattering the glass into small particles, establishing well circulation for wellbore conditioning and cementing operations. The optimal location of the flotation device is determined based on the well trajectory, casing design and fluid types.

In an ERD well, the challenging wellbore geometry and extended lateral section were identified as major risks that could prevent the completion from reaching TD. The well had more than 10,000 ft of an 8-1/2″ open-hole section, and was planned to be cased off with a 5-1/2″ production casing. The completion string could not reach TD during the first run of deployment, resulting in a decision to pull out of the hole and re-run the completion string with a flotation device in the configuration.

The solution deployed a tempered-glass flotation device, dramatically improving the run-in-hole effectiveness of the completion string, resulting in a successful run to TD. During the second run, the completion was installed successfully with significant reductions in side forces, buckling effects, as well as no operational issues were observed while running through the highest dogleg interval in the open hole (3.6-7.2 degree/100 ft).

This installation was supported with the use of torque and drag software allowing the flotation effects to be modelled, compared against the nonfloated completion optimized based on floatation device placement location.

Some of the flotation device novel features in wells with challenging high angled dogleg well profiles are: reduction in drag forces faced while running into the open hole (~30% reduction) and improvement in the relative stand-off percentage of the completion string (165% improvement), which comes from reducing side forces (lateral forces) and buckling effects faced while running into the open hole.

After successful deployment, fullbore access was granted by shattering the tempered-glass flotation device to small diameter (5-10 mm) particles that can be easily circulated out of the completion.