NAFTA's drillers have experience not only with drilling shallow wells, but also with wells which reached pre-Neogene formations at approximately 4000 to 5000 m. In total, 125 wells reached those formations. We are proud that we were able to plan, drill, supervise and evaluate Šaštín – 12, the country's deepest well, which was drilled to a T.D. of 6 505 m. Our team is involved in assessing the potential of exploration acreage, in proposing new field wildcats, in appraising, developing and producing discoveries and renders support to the UGS projects group.
NAFTA's E&P group discovered in total 26 oil and gas fields, whereby the bulk of oil and gas reserves was found during the time period from 50´s to 80´s. All producing fields were – or still are – operated by NAFTA. Peak oil production attained 0.63 mmb per year in 1963; the highest annual gas production reached 1.3 bcm, in 1959.
During the last 10 years we acquired 11 blocks of 3D seismic data in the Vienna Basin and in the East Slovakian Basin, covering a total area of 1 150 sq. km. At present we operate exploration licenses covering 2 360 sq. km and production licenses exceeding 300 sq. km in size.
Based on the long lasting E&P activities, a comprehensive database was generated which, owned by NAFTA, obviously represents a unique, valuable asset and which is being used by NAFTA in its everyday operations. Evidently, the data base is increasingly becoming important in other projects, such as carbon dioxide sequestration studies and geothermal projects.
From the year 2002 onwards, after change of shareholders structure, we welcomed colleagues from E.ON Ruhrgas and Gaz de France (today GDF Suez) and we employed international evaluation standards and exploration project risk management. Since then, we have drilled in total 31 wells with a 55% success rate. We would particularly highlight year 2012, with a 71% success rate and 5 successful wells.
Drilling of our prospects and fields, including workovers, is being performed by NAFTA's own drilling department. Thanks to proper drilling management, we achieved to remain about 7 million Euro under budget plans in the post-2004 time period. Our drilling rigs have performed operations outside Slovakia on several occasions.
Besides E&P drilling we supported and successfully managed UGS directional drilling for our UGS centre Gajary-báden, and we are currently contributing to the preparations of activities in the geothermal area.
71% success rate Year 2012 ended with a 71% success rate and 5 successful wells.
6 505 m deep Šaštín – 12, the country’s deepest well, which was drilled to a T.D. of 6 505 metres.
3D seismic data We acquired 13 blocks of 3D seismic data in the Vienna Basin and in the East Slovakian Basin, covering a total area of 1 150 sq. km.
3200 wells So far, approximately 3 200 wells have been drilled.
The involvement of our reservoir engineering group in all phases of production, i.e. from field planning to field life extension, has a long lasting tradition in our company. Upon application of technology optimization, of infill drilling and of proper design of drilling geological workover wells, we extended the production life of existing fields by 8 to 10 years.
In field operations, we have applied a couple of EOR methods, each of them designed to address the reservoirs' particularities:
‒ Secondary recovery techniques: (i) Air injection (used in the Gbely and Stefanov oil fields); (ii) Natural gas injection (Gajary Badenian oil field); (iii) Pattern water flooding (Petrova Ves, Studienka and Dubrava oil fields) and (iv) Barrier water flooding (Gajary Badenian oil field)
‒ Tertiary recovery technique: In-situ combustion (Gbely and Stefanov oil fields)
Outstanding E&P and UGS projects having been coped with by our reservoir engineering team were:
− the conversion of about one quarter of the depleted fields into underground gas storages (UGS), thus substantially adding value to the company assets,
− increasing the company's UGS capacity by adding 0.3 bcmg to existing storages, and developing additional storage objectives / reservoirs to a planned capacity of 0.5 bcmg,
− the preparation of production from the tight gas field Trebisov in the Eastern Slovakian Basin
EOR Via production optimisation and reservoir management, we have extended the production life of existing fields by 8 to 10 years.
25% conversion We were able to convert about one quarter of the depleted fields into underground gas storages.
Increase of our UGS capacity By proper field management, NAFTA achieved increase of its UGS capacity by 0.3 bcm and NAFTA are developing additional storage objectives to a planned capacity 0.5 bcm.
Technology and Investment
In NAFTA, both the implementation of production optimization projects and the management of safe operations is given particular attention, they are in the hands of a group of dedicated specialists, the “Technology and Investment” group.
Good examples of the professionalism of that group are (I) the implementation of production optimization measures such as the creation of treatment centre twins/triplets. (ii) the safety management of fields coping with H2S, e.g. Závod and Trebišov, and (iii) the rigorous remedial measures in surface P&A activities, which were implemented some ten years ago and by which the company's corporate responsibility approach is also visible to the public.