This is the world's first field trial where inflow tracers have been permanently integrated into a cased, cemented and then perforated production liner; previous inflow tracer deployments have been into non-cemented lower completions. This field trial took place for an oil production-well in the Vigdis field located in the North Sea. The objectives for the tracer deployment for the field trial were:
To demonstrate a tracer deployment method not causing complications during Run-in-hole or cementing, while allowing tracer marking of produced oil and water.
To demonstrate inflow tracer monitoring specifically for cemented liners
To improve the understanding of inflow and reservoir dynamics specifically for this well and the Vigdis field
Inflow tracers are unique tracer chemicals suspended in a plastic material, designed to release by liquid contact. These were deployed in a metal chamber at the outside of the production liner, to protect from the cementing operations. The liner joints containing the tracers were then spaced out at strategic locations across different reservoir intervals, and the production liner was cemented in place. After perforating, the tracers were exposed to flow, allowing surface sampling and later analysis of each unique tracer. Inflow along the wellbore was then determined through the use of sophisticated tracer transport models.
To ensure the success of this first field trial, the following items were specifically explored:
Care was taken to build the customized metal chamber with a smaller outer diameter than the couplings used for the 7inch liner, and to fill this with low solid oil-based mud. The integrity of the tracer systems and the deployment method were proven by:
No complications were observed during Run-in-Hole (RIH) or cementing
All tracers were detected with strong signals in liquid samples,
Tracer transport models were applied to the tracer signals and related production data, enabling:
Identification of the location of early water inflow
Defining which of two reservoir layers held the highest pressure
Verifying contribution from the toe during cleanup