First Application of Cemented, Single-Ball-Shifted Multiple Sleeves for Stimulation of Velkerri Shale
Authors: Ishmeev T. 
Published: October 2023

Increasing the horizontal lateral length of a shale gas well is often seen as a productivity improvement and project economics solution but challenges completion options. Long horizontal wells restrict popular plug and perf (P&P) stimulation techniques. Access to the toe section of the well is limited by coiled tubing reach. We share a case history of the Beetaloo basin completion of a 4,450 m Measured Depth (MD) horizontal well without an intervention. Cemented multi-point hydraulically actuated sleeves with erosion-resistant nozzles provided means to stimulate an extended reservoir section successfully.

To overcome the limitations of the P&P operations in a long horizontal lateral, a first-in-the-region completion technique was implemented. The solution permits a well integrity test after cementing the liner and is reliably functioned without intervention in a cemented casing. A multi-point ball-drop actuated system was proven to be an effective completion to stimulate the reservoir where coiled tubing could not reach.

A hydraulically-actuated toe assembly was deployed to access the deepest section of the reservoir without intervention. The toe assembly is designed to permit the liner cementing prior to arming itself at a designated pressure to shift open. Once opened, the assembly provided the first communication path from the wellbore to the reservoir. An injection test confirmed communication with the reservoir, and the required data was obtained during the test. After the toe section was stimulated, a single actuation ball consecutively shifted four sleeves installed in the second stage. The same ball isolated from the initial toe stage. Erosion-resistant nozzles provided limited entry treatment fluid distribution. Treatment effectiveness was confirmed using gas and water chemical tracers.

This paper publishes lessons learned about horizontal cemented liner completion system with ball-shifted sliding sleeves in a gas reservoir where intervention options were not feasible. The liner passed a pressure test and facilitated communication from the wellbore to the reservoir at the well toe and allowed specific reservoir zones to be hydraulically fractured in the largest treatment in Australia. We have demonstrated the ability to breakdown formation in a complex stress regime without perforating through the zone of near-wellbore stress concentration. Reducing over-displacement volume can be achieved with ball-drop completions. The observed increased pressure on subsequent injections into the same stage could be avoided during future operations by performing treatments in one continuous operation.

The project resolved multiple challenges, such as reaching the distant well toe, cementable tool design, and distribution of the stimulation fluid across four sleeves with designed erosion-protected nozzles. Additional achievements were recognized, including interventionless completion and stimulation operations, increased efficiency, and reduced carbon dioxide footprint. The implemented solution has provided a proof of concept for a multi-point, multistage well completion option in long horizontal, cemented wellbores.