Due to low sand strength the preferred completion method for the Heidrun field is gravel packed screens. This has proven to be a well suited sand control method. However, some failures have been encountered with the subsequent loss of the well or a reduced production rate due to sand production. Some of these failures are related to water break through which can induce the production of fines and result in plugging and erosion of the sand screens. When these type of failures result in the onset of massive sand production, it is a challenge to handle the well properly. How do we best produce the well to avoid it being filled with sand, and how do we best identify the point of failure? Identifying a failed sand screen is not straight forward since it is situated on the outside of a perforated base pipe, and no direct measurements can be achieved.
This paper describes a method used on several wells in the Heidrun field to mitigate failures in gravel packed screens. The method described, includes; how to identify sand production, the preferred way to run the well after sand production has been identified and how to perform data acquisition to determine the point of failure. The data acquisition described includes gravel pack logging, injection logging and saturation logging.
This method has been used with success on several wells in the Heidrun field, wells which would have been considered lost otherwise.
The Heidrun field is located on Haltenbanken in the Norwegian Sea. The sea depth in the area is 350m. The field has been developed with a floating concrete tension leg platform (TLP), installed over a subsea template with 56 well slots. The northern part of the field is developed with 5 subsea templates. The field's oil and gas production started on October 1995.
The reservoir consists of sandstones in the Garn, Ile, Tilje and Aare formations of Early and Middle Jurassic age. The reservoir is heavily faulted. The Garn and Ile formations have good reservoir quality, while the Tilje and Aare formations are more complex. Most of the formations produced on the Hedirun field have a moderate to low sand strength, and are prone to sand production. Several approaches to sand control has been tried, and the current base case solution is open hole gravel packed screens.
The recovery strategy for the field is pressure maintenance using water and gas injection.