The Prinos Oil Field is the main structure in the Prinos-Kavala basin, located offshore in the Gulf of Kavala. It covers an area of 4 km2, about 8 km north-west of the island of Thassos and 18 km south of the mainland of North Greece, in a water depth of 31 meters. Today, Prinos 2P reserves stand at 11,7 mbbls (2P), which are independently audited. Following the wells drilled in the context of the ongoing drilling programme and the interpretation of the 3D seismic data acquired in the summer of 2015, Energean estimates that there are 10 more million barrels of 2P reserves in Prinos and waits for the independent audition. The 2C contingent resources associated with a notional extension of water injection are 24.7 mln bbls.
Since the summer of 2015, “Energean Force”, Energean’;s own drilling rig, has been executing a 7-well drilling programme in the field, as a part of a new 200-million-dollar investment. After the completion of the drilling of four wells (PA-35A, PA-40, PA-36 and PA-41), production rates exceeded 4,500 bopd of medium grade sour oil plus associated gas. Currently, fourteen wells are producing and four are injecting sea water. After the completion of the drilling of wells PA-40, PA-36 and PA-41, Prinos’oil production averaged 3,177 bbls daily in 2016, that is a 151% increase compared to 2015 production.
The Prinos field is formed by a low relief faulted anticline, with oil trapped in the Prinos Group reservoir of Miocene Age at a depth of between 2490 and 2770 m TVDSS. The reservoir produces under-saturated sour crude oil with an API gravity of between 27 and 30 degrees. Prinos contains up to 60% hydrogen sulphide gas. The onshore ‘Sigma’ plant complexity is driven by facilities to remove this toxic gas and convert it to Sulphur. Sulphur is sold to a local fertilizer plant. Excess gas is sold to the same company.
The Prinos basin was explored in the 1970’s and the Prinos field was discovered in 1974, through the drilling of Prinos-1, the first exploration well drilled in the area. It was developed in the late 1970’s and brought into production in 1981. The initial development of the field, following the drilling of the delineation wells which confirmed the extent of the Prinos reservoir, took place from 1979 until 1981. Facilities were installed offshore and onshore to allow 30,000 bopd to be produced along with associated gas. Two drilling jackets were installed above the Prinos field, bridge linked to an unmanned offshore processing platform. These offshore facilities were linked by pipeline to shore where a complex gas and oil processing plant was constructed along with oil storage tanks (500,000 bbl capacity) and offshore loading terminal. Crude oil production commenced in early 1981, at initial rates of 8,000 to 10,000 bopd. Production peaked at more than 27,000 bopd in 1985, however it has steadily declined since then. Prinos 2P reserves were initially estimated at 60 million oil bbls, but the field has already produced almost 110 million bbls since 1981
The Epsilon Oil Field has 15,3 mmboe 2P reserves which have been audited by ERC Equipoise. STOIIP is estimated at 39mmboe while the recovery factor stands at 1%, as only 300,000 mbls were produced in 2010. The interpretation of the 3D seismic data acquired in 2015 is under process and it is expected that will result in increasing the estimated STOIIP and 2P reserves. Energean has planned to develop the field through a new development project which consists of: (1) The design, fabrication, installation, commissioning and subsequent operation of a new well-head jacket platform (called “Lamda”) approximately 3.5 km’s NW of the existing Prinos platforms. Lamda has been designed to be normally unmanned; (2) The installation of three sub-marine pipelines that connect Lamda to Prinos Delta: (3) The drilling of 5-9 wells. This new development plan will cost approximately $50 million for the jacket and pipelines and approximately $60 million for the wells.
The Epsilon oil field is an anticlinal structure some 3 km to the west north west of the Prinos oil field. The field was discovered in 2000 when Well E-1 tested sour crude oil with an API gravity of 36 degrees in reservoirs belonging to the Prinos Group at a depth of about 2800 m TVDSS. The well was side-tracked a year later to a location some 500 metres to the south east, confirming the reservoir presence and tested oil.
Exploration activity in the Epsilon field area began in the 1990s, when the anticlinic Epsilon structure was identified by interpretation of 2D seismic data. The area remained a low priority, and was only partially covered by the 1993 3D seismic cube. The 3D seismic survey acquired in 1997 however, covered the whole area, and made it possible to map the structure, and consequently upgrade Epsilon as a high priority exploration target. The field was discovered in 2000 when Well E-1 tested sour crude oil with an API gravity of 36 degrees in reservoirs belonging to the Prinos Group at a depth of about 2800 m TVDSS. The well was side-tracked a year later to a location some 500 meters to the south east, confirming the reservoir presence and tested oil. Energean drilled an extended reach multi -lateral well, EA-H1, which was successfully completed in January of 2010 and produced for a 12 month period cumulative oil production over 0.3 MMbbls. The length of the well reached 5,297 m, with more than 450 m horizontal section of each leg, being thus far the longest well in the Mediterranean. A geophysical campaign took place in Q3 2015 as part of the Epsilon development project. A detailed bathymetry survey of the area affected by the Epsilon project was conducted and used as input for both the design and ESIA work stream.
On November 2015, Energean was awarded a 3-year extension in the duration of South Kavala license and has been preparing a new development plan for the period 2017-2019 that will cost approximately US $1.5 million. The project is under evaluation and includes the installation of down-hole pumps in two of the existing wells to remove liquids from the well bores and will enable the field to be placed back into continuous production, increase condensate yields and bring recovery eventually up to 98.5%, as the remaining gas reserves are approximately 2.6 Bcf.
The South Kavala Field was discovered by SK-1, the first exploration well drilled in the Basin in 1972, in the same initial exploration campaign that found the main Prinos oil field and Zeta. The structure was confirmed by 6 more exploration and appraisal wells. It was developed in parallel to Prinos as a remote satellite during the period 1979-1980. Two producing wells are active since then, with an average total depth of 2,050 meters. A single well jacket was installed and linked back to Prinos with a 12” pipeline. South Kavala contained approximately 1 BCM of sweet, lean gas. It was developed to supply fuel gas to Prinos and the onshore plant. In the 1990’s wellhead compression was added to the jacket to maintain production.
The USP Project
The depleted field is suitable to be converted into an Underground Gas Storage (UGS) linked to the TAP pipeline that will transit Greece 2km from Energean’s onshore processing plant. Energean has submitted on 1st July 2011 to the Regulatory Authority of Energy (RAE) an application for the acquisition of a license that permits the installation of the storage and the conversion of the almost depleted field into a UGS, in accordance to the Law No 3428/2005 (relates to the release of the natural gas market in Greece.)This development is on hold awaiting approval from the Greek government. Conversion to UGS would require an investment of approximately initially estimated at US $400 million.
The key characteristics of the project are as follows;
• Investment of €350 -400MM
• Working gas volume 530×2 MCM, with annual Working gas volume 1 BCM, delivery of minimum 2 cycles per year, with a duration of up to 90 days
• Maximum injection 7 mln m3/day
• Pipeline gas for fill-up and operations
• Existing Kappa Platform with new 32 km high capacity pipeline to Sigma site
• 5 wells; 7″ completion; min THP 18 bar
South Kavala is considered a strategic location for the stability of the country and region’s energy supply. The UGS project was adopted by the European Commission as a Project of Common Interest under Regulation (EU) No 347/2013 on Guidelines for trans-European energy infrastructure, but since there are no decision from the Greek State, it was excluded from the list.