This article is extracted from PESGB Monthly Newsletter, January 2007 and republished with permission.
Recent Exploration in the Carpathians – Revival of the
“Vintage” Terrain?
Piotr Gawenda and Helena Dobrova - IHS, Geneva, Switzerland
Summary
The sedimentary basins of the Alpine-Carpathian mountain belt extend from France to Romania. The eastern extension of the chain, containing prolific hydrocarbon provinces known since the mid-XIX century, still represents an important exploration area in several countries. Although mature, the basins of the Czech Republic, Poland, Slovakia, Ukraine and Romania attract considerable interest following the political changes in the early 1990s and application of the latest petroleum-related technologies. Since the late 1990s, a growing number of small- and medium-size independent companies seeking E & P opportunities operate in the area. During the 2000 – mid-2006 period, numerous new exploration permits were granted, 2D/3D seismic programs were recorded and over 250 exploratory wells were drilled, resulting in some 150 successful operations. The bulk of the action occurred in Poland (125 wells) and Romania (over 110 wells). Significant new discoveries of the period are e.g. Jasionka, Terliczka, Trzebownisko, Stobierna in Poland, and two Bilca wells and Fratauti in Romania. The remaining hydrocarbon potential is believed to be principally associated with the prospects at greater depths, sub-thrust plays, stratigraphic traps and trailing plays involving redefinition of existing geological concepts.
Introduction
The sedimentary basins in the eastern part of the Alpine-Carpathian mountain belt extend from the Czech Republic to Romania across Slovakia, Poland and Ukraine, stretching from the west to the south-east for over 750 km (Fig. 1). Following break-up of the Pangea supercontinent, the basins and their substratum underwent a series of tectono-stratigraphic pulses. The last major phase of crustal development (Africa-Eurasia convergence) resulted in a diachronous formation of multiple fold-and-thrust mountain systems and their respective foreland basins.
Figure 1: Simplified map of sedimentary basins along the Alpine-Carpathian mountain belt with focus area marked red (valid concessions included).
Several basins in the region, being known prolific hydrocarbon provinces since the mid-XIX century (e.g. the flysch/foredeep successions in Poland and Romania), remain major targets of exploration today. Some 10,000 wells have been drilled in the region. The exploration efforts resulted in the discovery of at least 55 fields in the Czech Republic, 20 in Slovakia, 165 in Poland and 275 in Romania, with total recoverable reserves of over 7 Bbbl of liquids and roughly 20 Tcf of gas (Fig. 2).
Figure 2: History of reserves additions in a) Czech Republic, Slovakia, b) Poland, c) Ukraine and Romania. Main discoveries indicated.
After political transformations in the early 1990s, markets opened in the central-eastern European countries. Following these changes, major international explorers showed interest in the newly opened acreage, but subsequently, they gradually pulled out of exploration in the area. Since the late 1990s, importance of small- and medium-size independent companies seeking E & P opportunities has been growing. Some of these companies carry out ambitious high-risk, high-reward exploration programs, often with astounding results. Additionally, many view rehabilitation of the vintage oil and gas fields, non-economic for larger domestic and international companies, as a viable commercial option. Interestingly, larger international operators are now taking a new look at the area.
Since 2000, some 250 exploratory wells have been drilled, of which approximately 150 have been reported as successful. The bulk of the action was recorded in Poland and Romania (some 125 and over 110 wells, respectively). The most significant discoveries of the period include Jasionka, Terliczka, Trzebownisko, Stobierna in Poland, as well as two Bilca wells and Fratauti in Romania. The following paragraphs include an overview of the exploration efforts in the Carpathian basins, highlighting recent significant events (Fig.3).
Figure 3: Overview map showing location of concessions, wells and fields cited in text.
Czech Republic
The principal explorers within the Carpathians are domestic Moravske Naftove Doly (MND), Unigeo, Ceska Naftarska Spolecnost (CNS) and Australia-based Carpathian Resources. Since 2000, the contractual situation has remained busy, with awards of numerous exploration contracts (e.g. Svahy Ceskeho Masivu, Morava, Frydland nad Ostravici-Celadna). Since 2004, MND has acquired three 3D seismic programs in the Svahy Ceskeho Masivu permit, including a 150 sq km seismic project in 2006. Another program, Uhrice NW, is underway. Also, some 25 exploratory wells have been drilled. Most of these wells were located in the proximity of the existing oil/gas fields - Damborice, Uhrice, Zarosice. During 2005, Carpathian Resources recorded 2D seismic over its Janovice, Roznov and Morava project areas, put the Janovice field on-stream and abandoned dry well Janovice 11. Year 2006 seems “quiescent”, but, in 2007, the company intends to develop the Janovice field following a reserves upgrade and drill a well on a “large” structure with gas potential. Earlier, in 2003, RWE Transgas completed Dunajovice P1 as a discovery.
Slovakia
The principal exploration terrain is located within the Vienna Basin and the tectonic elements of the Pannonian Basin, with a minor part of the prospective area situated within the Carpathians. At present, solely foreign companies are operating there. In 2005 and early 2006, Wharf Resources purchased acreage in northern Slovakia from domestic Slogold and, since August 2006, there is Aurelian Oil & Gas of the UK. Exploration activity in the region remained limited in the past few years: only the Alexander 1 well, drilled by Vyskum & Vyhladavanie N & P Bratislava in 2003, was situated within the Carpathian limits. However, the newcomer Aurelian is hoping to swiftly instigate exploration programs in the eastern part of the country (Carpathian Flysch Zone), where it had acquired the Medzilaborce, Svina and Svidnik permits.
Poland
The main operators in the Carpathians, where almost the entire prospective area is under license, include domestic PGNiG, Medusa (100% subsidiary of RWE Dea) and Eurogas. PGNiG concentrates its activities primarily in the Outer Carpathian Foredeep, with few undertakings in the Carpathian Flysch Zone. Since 2000, the company has completed almost 4,000 km of 2D and approximately 650 sq km of 3D seismic. Some 125 exploratory wells have been drilled in the past five years, placed primarily close to the existing Zolynia-Lezajsk, Jasionka, Kupno and Wola Rozaniecka gas fields (note that many outposts, or new-pool wildcats drilled by PGNiG should be classified as development wells according to international standards).
Important new discoveries during the period include Grodzisko Dolne (2000), Stobierna (2000), Terliczka (2000), Jasionka (2001) and Trzebownisko 3 (2003). Although PGNiG shows good success in discovering new gas pools, findings are small, usually less than 1.5 MMboe. For this reason, the company started drilling deeper wells – Huwniki 1 (PTD below 5,000 m) - aiming at sub-thrust structures.
Eurogas and Medusa hold acreage within the Carpathian Flysch Zone. Following the 2002 Zdynianka 1 and 2003 Ropa 1 wells, both non-commercial gas discoveries, Medusa ran some 80 sq km of 3D seismic in late 2005 to resolve internal structures of the flysch series. Since mid-2006, the company is engaged in a two-well drilling program: deepening of the Ropa discovery is underway and another well is planned in the neighborhood. Eurogas intends to start exploration in the Bieszczady tract.
Ukraine
Little data is available on recent exploration activities in western Ukraine. Apart from the 2005 discoveries of Dubanevitske and Dibrovske, Ukrgazvydobuvannya, a subsidiary of Naftogaz Ukrainy active in the Lviv region, reported two new discoveries Dobryanske (oil) and Lugovske (gas) for the period January-August 2006. Foreign operators are scantily represented in western Ukraine. In September 2006, the Swedish oil company Capital Oil signed a preliminary cooperation agreement with the Ukrainian state-owned company Bogorodchanynaftygas for joint development and production of a number of oil fields in western Ukraine.
Romania
To date, over 7,500 MMboe have been discovered in the Romanian Eastern Carpathians (Carpathian Foredeep and Carpathian Flysch Zone; Fig. 2). Almost the entire prospective area is currently licensed, with the main operators in the studied region being Petrom, Romgaz, Aurelian Oil & Gas (former Falcon Oil & Gas), Rompetrol, Toreador, Europa and Amromco. One of the significant rightholding events of the period under review is the acquisition of Romania’s Petrom SA by OMV AG of Austria in 2003. Licensing has been very busy: since 2003, the country’s 5th, 6th and 7th licensing rounds have been organized for exploration as well as production acreage, the 8th round being scheduled for early 2007.
On the operational side, in the last five years, more than 13,000 km of 2D seismic and 450 sq km of 3D seismic have been acquired. Of this total, at least 3,400 km were acquired within the Carpathian area. Also, over 110 exploratory wells have been drilled (information on Petrom’s wells is incomplete), resulting in at least 23 discoveries, including those deemed non-commercial. In recent years, Petrom continued recording 2D seismic and, following OMV’s experience from the Vienna Basin area in Austria, in 2005 started a series of 3D seismic programs, which continued into 2006 (Targoviste). Since 2003, Aurelian Oil & Gas has acquired several 2D campaigns in the Brodina, Bacau and Cuejdiu blocks. In 2005, Rompetrol ran its first 2D seismic in the Zegujani block. Toreador is preparing to start its multi-well drilling campaign in the southern part of the Viperesti block in 2007.
The most important discoveries were Aurelian’s Bilca 1, Bilca 2 and Fratauti 1 drilled in 2004-2005 (Fig. 3). All tested commercial gas and, in September 2006, they commenced production. Tullow’s first well Costisa 1 and sidetrack Costisa 1Z drilled in 2005 were unsuccessful; Costisa 1Z is scheduled to be re-entered for additional testing in late 2006.
Concluding Remarks
Despite decades of exploration history, the Carpathians remain an area of considerable interest even today. Creaming curves (Fig. 2) show that little “new oil” has been added to the existing hydrocarbon reserves since the mid-1970s (in Romania ten years later). Apart from Poland, a diachronous gas plateau is observed for the majority of the basins since the mid-1980s.
Although it seems that the current strategy of some domestic operators (e.g. in Poland and Slovakia) is oriented towards maintaining the existing production levels from progressively aging fields, new discoveries, small in most cases, are still being made (Fig. 3). These discoveries result from a redefinition of vintage concepts, better imaging of the subsurface using latest seismic techniques, and from a better understanding of a complex interplay between tectonics and stratigraphy in compressive systems.
The remaining hydrocarbon potential in the Carpathian basins is believed to be associated primarily with the prospects at greater depths, sub-thrust plays and subtle stratigraphic traps. In the latter case, improved exploration results are expected following the deployment of 3D seismic on a larger scale.
For further information on this article or on IHS, please contact andrew.hayman@ihs.com (+41 22 721 1717)