Epsilon Oilfield, Aegean Sea

The Epsilon oilfield lies at a water depth of 30m in the Aegean Sea. Discovered in 2000, the field is owned and operated by Energean Oil & Gas (formerly Aegean Energy), and situated approximately 4.2km north-west of the Prinos oilfield.

Energean Oil & Gas has the concession rights to develop the field along with Prinos and South Kavala oilfields..

Epsilon geology and reserves

Miocene sandstones are primarily found in the Epsilon field. Oil of the asphaltic type with sulphur content is mostly found in three areas of the field, namely, Epsilon Main, Epsilon North and the Prinos West Flank area. The quality of oil at the field is similar to that of Prinos, North Prinos and Ammodhis.

Epsilon contains immature oil with a high proportion of hydrogen sulphide and carbon dioxide. Its oil reserves are estimated to be over 30 million barrels.

Prinos development

Greece’s Minister of Development agreed to the development of the Prinos area reserves, including the Prinos field, in April 2008. The development involved the drilling of production and water injection wells for an effective recovery rate, and the fabrication and installation of a fixed platform, which was then connected to the Prinos offshore platform, Delta.

The field development started with its first well, Epsilon-1, which was drilled in 2001 without any operational issues, and reached a total depth of 2,981m in an 8.5in hole. In addition, drill stem tests were carried out to confirm a major oil discovery; however, due to mechanical problems, permeability was impaired. The drilling was completed in 62 days.

The well was suspended and re-entered in 2002, and at this stage was referred to as Epsilon-1A. It was redrilled as a bottom-hole assembly and stuck in the object linking and embedding for process control stage in an 8.5in hole at 2,985m.

The well, later referred to as Epsilon-1AS, was drilled to 3,125m and tested. Dry oil was produced from a 6m-deep layer between the oil well and reservoir. The maximum production rate achieved was 1,000bpd.

Electric logs in the original Epsilon well-1 outlined the presence of a minimum of three distinctive reservoir layers compared with only one thick layer in Epsilon-1AS, along with improved reservoir characteristics. The Epsilon-1AS well had a permeability of 12mD and was suspended.

The second phase of drilling started in September 2009 as per the development plan approved by the Ministry of Development. Ensco 85 was selected as the jack-up rig for drilling operations. At the same time, the company signed a finance agreement with Standard Chartered Bank and appointed Schlumberger for drilling management services.

Drilling of the first well, EA-H1, was completed in January 2010. The 5,500m-deep well, which is considered complex, is the longest well drilled in Greece. The drilling was completed within three months.

Energean will develop the field in the future. The development plan includes the installation of a dedicated unmanned platform which will be connected to the Prinos processing platform. Oil will be recovered through water injection.

Epsilon production

The Epsilon project came onstream with the start of the EA-H1 well’s production in January 2010. Epsilon is the first new field in production in Greece in the last 14 years.

By the end of 2009, the field was producing at a rate of 4,000bpd. Energean contracted the GSP Saturn jack-up rig to carry out drilling of new wells and interventions. This will increase the field’s total production to up to 5,000bpd.

Jack-up rigs

The first well was drilled by the Ensco 85 jack-up rig. The rig, which is owned by ENSCO and designed by MLT-116-C, was built in 1981 at the Marathon Letourneau yard in Singapore. The rig has a total drilling depth of 25,000m and can accommodate up to 106 people.

Energean signed a contract for jack-up rig Energy Exerter with Northern Offshore Limited in November 2008. The rig is one of the toughest jack-ups in Energy Exerter’s offshore fleet.

The Energy Exerter rig is specifically designed for operations in the North Sea at water depths up to 300ft and a total length of below 112m. The independent leg cantilever-type jack-up rig has a power of 2,000hp and can drill at a depth of 7,500m.