Full Field Subsea WAG Development

Background and Subsurface Setting

The Snorre Area in the Norwegian North Sea consists of the Snorre, Vigdis, and Tordis fields. With production starting in August 1992, the southern part of the Snorre field is developed with a floating tension leg platform (Snorre TLP) and a subsea template. The northern part of the field, the Snorre B, was put on production in 2001 and is developed with a semi-submersible production installation.

Challenge

The Snorre reservoir has a complex structure with varying properties and many flow barriers. Several measures have been implemented in order to increase oil recovery. Extensive use of water-alternating-gas (WAG) injection has contributed to increased oil production. A large-scale pilot project with foam injection (FAWAG) yielded promising results. Reservoir and individual layer production control has been successfully tested on Snorre.

In several areas of the field, individual sand bodies are proven to be non-continuous. The permeability contrasts are significant and faulting changes the flow patterns. All of these factors significantly complicate the reservoir drainage and pressure maintenance strategies. To optimize oil production rates, as well as ultimate reserves recovery, the flexibility provided by remote zone control completion equipment is crucial in these areas.

SmartWell^® Solution

The Snorre B field development is, to a large degree, based on well completions with WellDynamics' SCRAMS® zonal flow control. After the field was put on production, reservoir pressure declined, and water injection was started in February 2002. Both the C-2H and C-6H wells are in communication with the reservoir layers in the water injector, K-4H, and possibly with the WAG injector, K-6H. The K-4H injector and the K-6H injector were completed with the four-position interval control valve (4P-ICV) in four isolated zones.

Customer Value

The pressure response from the water injector K-4H could be observed after one week in well C-2H. The production rate increased after injection started in February 2002 as a result of arresting reservoir pressure decline and optimizing the water injection in K-4H. The produced water cut has been stable at 14%.

The injection control into the various zones that is enabled by the SmartWell® completion has proven to add significant value to the reservoir development. Reservoir modeling of Snorre B demonstrates that conventional sweep efficiency will cause water breakthrough at an early stage in the reservoir's life. Installation of an intelligent injection system has already made a significant improvement to the reservoir sweep efficiency, and will continue to do so as the flexibility that the completion system offers is fully utilized.

Details