Laboratory tests using a lubricity meter showed that the new ADFR fluid provides better lubricity than commonly used products. (All graphics courtesy Halliburton)

Achieving the benefits of coiled tubing (CT) operations in the extremities of today’s extended-reach wells can be difficult and expensive. Overcoming the frictional forces — drag and torque — that are encountered as the CT is pushed into the well bore often requires the use of tractors: hydraulically operated devices that literally pull the CT into the well bore.

The forces encountered can greatly reduce the amount of set-down and pick-up force that can be applied to the bottomhole assembly (BHA) via the CT. They can prevent achieving the necessary horizontal reach with the CT. If the force that can be applied both in pushing and pulling the CT is significantly reduced, the ability to perform CT-based operations can be severely curtailed. Also, the additional drag and torque can shorten the life of the CT string, affecting both cost and reliability.

The new advanced drag friction reducer (ADFR) fluid addresses all of these challenges and makes CT operations in extended-reach wells more viable, efficient, and economical. The ADFR fluid serves as a lubricant that eases the movement of the CT string in and out of the well bore.

The lubricating property of the ADFR or any fluid is expressed as the lubricity coefficient. The new lubricating technology provides several advantages:
• Enables CT operations in extended-reach deviated and horizontal wells without a tractor;
• Enables higher set-down and pick-up force at the BHA;
• Compatible with fresh water and NaCl (sodium-chloride) or KCl (potassium-chloride) brines;
• Highly water-soluble, non-polymeric gelled fluid can be easily removed if necessary;
• Enhances capabilities of tapered CT;
• Formulations can be tailored for both carbonate and sandstone formations;
• Can be used to help improve the lubricity of completion and workover fluids;
• Applicable up to 300°F (149°C); and
• Effective in cased hole and open hole.

The new ADFR fluid was tested using a lubricity meter and industry-standard procedures. The results were compared to other products widely used for reducing mechanical friction. The ADFR fluid proved to show lower friction coefficients (Figure 1).

The new ADFR fluid can be batched or mixed on-the-fly, depending on the equipment used. The addition of nitrogen for use in low-bottomhole-pressure wells does not affect the friction-reduction properties of the ADFR system.

The ADFR has been used very successfully in several areas around the world.

Case History 1. In the Rocky Mountains an operator needed to set a plug because the well would not pressure-test. The first run into the well was with a mill and motor followed by running a setting tool and plug. The operator wanted to run in dry (using no lubricating fluid) on the first try but encountered a collar at 3,042 ft (927 m) requiring rotation of the mud motor attached to the end of the CT in order to pass through the reduced space adjacent to the collar. This occurred on three occasions. The
CT traveled to only 9,560 ft (2,914 m) before lock-up without pumping and to 9,775 ft (2,979 m) with pumping that provided some lubrication and caused the motor to rotate.

At that point, batches of the new ADFR fluid were pumped, resulting in enough lubrication to enable the CT to continue to the required depth of 9,951 ft (3,033 m). As more ADFR fluid was placed, much less force was required to reach the required depth with the CT. The plug was successfully set at 9,945 ft 3,031 m, Figure 2.

Case History 2. In the Middle East, ADFR fluid helped set a record of 9,775 ft for unassisted horizontal reach with CT. To maximize hydrocarbon recovery, the operator was drilling long horizontal wellbore sections and maximizing reservoir contact by perforating multiple lateral well bores. Completing these wells required the use of CT. The difficulty was that the complex wellbore architecture produced drag forces that had to be overcome for the CT to reach the end of the horizontal sections. Hydraulically operated tractors were replaced by using a relatively small quantity of ADFR fluid.

The operator became so confident in the performance of the ADFR fluid that the third-party CT hydraulic tractors were released from the job in spite of having additional wells yet to be stimulated.

The new advanced drag friction reducer fluid is available from Halliburton as CoilGlide service.