This paper will outline the challenges faced and solutions employed to enable selective stimulation of a pilot horizontal well in the Tengiz field by mechanical manipulation of fracturing sleeves utilizing an electric line deployed tractor system. Specifically, how the robotic system enabled successful and selective stimulation of nine acid fracturing stages in a challenging operational environment. The scope reviews the planning and execution methodology utilized to enable selective stimulation and production along the lateral section.
While evaluating the concept of drilling a horizontal well through a deeper, previously undeveloped reservoir horizon, it was identified that multiple acid fracturing stages would be required along a 1,000-meter lateral section. The well objectives were such that each of the acid fracturing zones required the ability to be selectively stimulated and produced (selective shut-off of zones post-production if required). This design utilized an open hole completion with compartmentalization via swell packers and fracturing sleeves. Due to the trajectory and horizontal nature of the well, electric line deployed robotics were selected to access the fracturing sleeves.
The well was successfully drilled and completed in 2019 and stimulated in early 2021. All zones were effectively accessed utilizing the selected intervention and stimulation methodology. This was the first use of a robotics intervention technique in the Tengiz field. It was also the first horizontal well drilled and completed into the target reservoir horizon. Intervention challenges included high pressure/high temperature, H2S, well restrictions, drilling muds (with weighting agents), and of course the trajectory of the well with ~ 1,000m lateral section to traverse. The successful outcome was a result of the conceptual engineering, planning and execution of the intervention and stimulation work scope. Formal surface integration test (SIT) was required to identify the best sleeve shifting options, which supported the procedure for the intervention scope. Valued lessons learned and best practices specific to the completion design, tractor deployment and stimulation strategy were gained through the testing and implementation scopes that will be utilized for future similar projects.