UNFC and National Classifications National Case Study - Poland

Transcription

1 UNFC and National Classifications National Case Study - Poland Marek Hoffmann - Polish Oil and Gas Company, Warsaw Stanisław Przeniosło - Polish Geological Institute, Warsaw Barnówko-Mostno-Buszewo and Kościan fields 1. Description of Fields Introduction Late 1990s extensive exploration for oil and gas provided in Western Poland with application of the newest technology, especially 3D seismic surveys, resulted in two significant discoveries (Fig. 1): Barnówko-Mostno-Buszewo called also BMB (oil, gas and condensate) and Kościan (gas). In the common opinion in that area rather small gas fields were expected. The experience showed that it does not have to be a rule. The BMB is one of the greatest on-shore oil fields in this part of Europe. The Permian Basin is the main target of exploration for oil and gas in Western Poland. Porous Rotliegendes clastics and two Zechstein carbonate formations: Zechstein Limestone (=Werrakarbonat) (Ca1) and Main Dolomite (=Stassfurtkarbonat) (Ca2) are the most important reservoirs. Every depositional system observed there, includes different lithofacies and create different patterns of the reservoir and sealing horizons. Combined traps, with both structural and facies elements involved in their closure, create a comparatively high risk of exploration. Geological setting The Permian Basin was formed in the Late Carboniferous - Early Permian as a result of subsidence and rifting mainly in extension tectonic regime. This process affected an area of Variscan orogenic belts and their foredeeps, and created systems of elevations and troughs. The Rotliegendes clastics formed as a result of erosion of Variscan orogen and early Permian volcanites filled the depressions. However, main tectonic features were still evident at the time of Zechstein transgression, and the morphology of the basin controlled facies distribution. Relatively high carbonate production in the marginal parts of the basin resulted in construction of progradational carbonate barriers during sedimentation of the Zechstein Limestone and the Main Dolomite formations. These are principal oil- and gas-bearing formations within the Polish Lowland. The Rotliegendes clastics, mostly aeolian and fluvial sandstones, and reeftype formations of the Zechstein Limestone produce gas. The sediments of the Main Dolomite barrier-lagoon depositionary system are oil as well as gas prone. The sedimentation of the reef-type build-ups of the Zechstein Limestone and barrierlagoon systems of the Main Dolomite is related to the NW edge of the Wolsztyn Swell. BMB oil, gas and condensate field The transgression of the Zechstein sea has invaded the area of diversified posterosional relief. During the first sedimentary cycle (Werra) intensive sulfate deposition proceeded in shallow-marine environments around elevations formed by

2 volcanites of the Wielkopolska Formation. Structures encountered in vicinity of Barnówko and Mostno can be interpreted as eroded volcanic calderas and system of tectonic fractures where lavas extruded. Expanding sulfate sedimentation covered the area and formed the sulfate platform. The platform has distinct boundaries. The extent of the Oldest Halite (Na1) salts determines the edge of a platform slope. The salt sedimentation on the platform proceeded in local depressions only. On the relief resulting of the Werra cyclothem sedimentation has transgreded the sea of the second (Stassfurt) cycle. The edge of sulfate platform has become the barrier zone of carbonate sedimentation which separated the relatively deeper sea from the shallow lagoon. The sea-floor relief played crucial role in facies development of the Main Dolomite. For exploration for oil and gas most important are carbonate sediments of the barrier zone, lagoon, and in particular conditions platform slopes. Both the depressions and the platform foreland sediments are regarded as barren. In the barrier zone formed oolite and oncolite carbonate sands of very good reservoir properties (porosity % and permeability md). These geological conditions resulted in formation of traps built of porous and permeable carbonates sealed by anhydrites and salts. Good reservoir properties decrease lagoon-wards due to facies change manifested in increase of micrite content in the deeper parts of the lagoon (Fig. 2-3). The very high quality of the data from 3D seismic survey resulted in record of three reflectors instead of only one observed till now. Detailed analysis of maps of these 3 horizons resulted in conclusion that primarily recognized three discoveries Barnówko, Mostno and Buszewo form a single, greatest in the Polish Lowland, reservoir mechanism filled with oil, condensate and gas. The reservoir properties vary within the whole system. The thickness of the reservoir series riches from 34 to 85.5 meters, and porosity from 2 to 26%. The whole reservoir thickness is oil or gas saturated and decrease of the net pay in Mostno-1 well is a result of dramatic decrease of porosity in 8-meter interval at the bottom. The total acreage of the BMB has been calculated as 32 sq. km, the average thickness as 48 m. Oil saturation is observed at the depth of m and the gas cap at the depth m. Oil gravity varies from API (798 kg/cub.m) at the top to API (828 kg/cub.m) at the bottom. Gas contains 43.7% of hydrocarbons, 52.57% of nitrogen and unfortunately 3.33% of H 2 S. The BMB reserves in-place have been determined as 488 MMbbl (64.4 MMt) of oil and BCF (29.4 BCM) of gas and recoverable reserves as MMbbl (10.1 MMt) of oil and BCF (9.9 BCM) of gas. The reserves estimations were provided on the base of minimum recovery factors. The total acreage and the reserves estimations allow to classify the BMB discovery as the largest oil field within Polish Lowland which total recoverable reserves have been estimated as MM bbl (11.49 MM metric tons) of oil and BCF (24.34 BCM) of gas. Dębno oil and gas production facility In December 1999 the biggest production project in the history of Polish petroleum industry production project - the Dębno Project - has been completed and started its production on The main scope of the project was development of Cychry, Różańsko and Barnówko- Mostmo-Buszewo (BMB) fields.

3 The main bulk client for gas is Elektrociepłownia Gorzów S.A. (Gorzów CHP) power plant - the first gas driven in Poland. The concept had to take into consideration the necessity of finding customers for all products, and the requirements of safe and environmental friendly production. In the Dębno Oil & Gas Facility (Fig. 4) stabilized crude oil ( BOPD), condensate (2.12 M stcfd), sweet natural gas (44.93 MM stcfd), LPG - propanebutane mixture (4.31 M stcfd), and high quality liquid sulfur (130 metric tons/day) are produced. The different feed parameters and the presence of H2S were the reasons for the application of unique and sophisticated, technological solutions. The whole system consists of 23 wellsites, 2 Group Centers: Sulisław (SGC), Buszewo (BGC), Cychry Gas Separation located at the wellsite, and Barnówko Main Center where separation and stabilization of final products takes place. The Barnówko Main Center (BMC) works in the following main technological units and process equipment: 1. High Pressure Inlet Separation where oil, gas and water are separated under high pressure; 2. Sour Water Treatment where the pressure of the separated produced water is reduced and methane, ethane, propane, H2S, and other gas components dissolved in water are separated; 3. Oil Stabilization where pressure of the separated oil is reduced and oil is degassed, and H2S is removed from oil in the distillation column; 4. Water Wash where solid particles are removed from sour gas; 5. Amine Sour Gas Sweetening where H2S is removed in process of absorption in 50% methyldiethanolamine (MDEA) and MDEA regenerated in H2S desorption process; 6. Low Temperature Gas Separation where sweet gas is chilled by liquid propane and separated in distillation columns; 7. Mercaptans (RSH) Removal where organic sulfur compounds are removed from liquid propane-butane mixture in an adsorption and desorption process on molecular sieves; 8. SuperCLAUS Process where H2S is burned with a precisely controlled amount of air and reduced to elementary sulfur in catalytic process; 9. Shell Process where liquid sulfur is degassed; 10. Tail Gas Incineration where tail gas from SuperCLAUS and Shell Processes is incinerated; 11. Acid Gas Recycling where acid gas from low pressure processes is recycled to the process; 12. Vapor Recovery Unit where light (vapor) hydrocarbons are collected from the oil, condensate and water storage tanks; 13. Storage system which consists of: water storage tank (capacity of 254 CM), condensate storage tank (capacity of 350 CM), three LPG bullets (capacity of each 225 stcm), two oil storage tanks (capacity of each 3500 CM). The whole system is fully automated and controlled by a specially designed computer systems located in production units at the field sites and in Barnówko Main Center. The application of the latest technologies, and strict control of the whole process guarantees the top quality of products and production safety. All elements of

4 production and transportation equipment meet the regulations of Polish as well as European Community industrial and environmental protection standards as well as the standards of American Society of Mechanical Engineers (ASME), American Petroleum Institute (API), American Society of Testing and Materials (ASTM), International Federation of Standardizing Associations, Instrument Society of America (ISA), American National Standard Institute (ANSI), National Association of Corrosion Engineers (NACE). In order to provide secure and stable gas supply to EC Gorzów (CHP) power plant an alternative gas delivery system have been constructed. The system is based on the gas from the Zielin field located nearby mixed with gas from the gas system. The alternative supply system have been used in initial production stages. Kościan gas field Gas accumulations in Kościan area are known since 1970 s. Development of exploration technology resulted in discovery of five gas fields in the area (Fig. 5-6). At the elevations of the sea bottom build of Carboniferous sandstones and/or early Permian volcanites developed series of shallow water, reef-type build-ups that have existed in association with oolite-oncolite sedimentation. In depressions between reeftype structures sedimentation of basin facies developed as thin (5 m) micrite limestones and mudstones. This sequence has been named as the Zechstein Limestone (Ca1). The carbonate formations of Ca1 are sealed by sulfates of the Werra Anhydrite (A1) and locally by salts of the Oldest Halite (Na1) formations. The second stage of field formation is connected with sedimentation of the Main Dolomite (Ca2) which is developed as a sequence of deeper sea grained, locally nodular dolomites at the bottom, and laminated marly, micritic and oolite dolomites and dolomitized limestones at the top. The Main Dolomite is sealed by a thin layer of the Basal Anhydrite (A2) sulfates and salts of the Older Halite (Na2). Gas accumulations are connected with both Ca1 and Ca2 formations. The reef-type structures of Ca1 are rather large and homogenous. The thickness of Ca1 varies from 22 to 67.5 m, the porosity varies from 10 to 19 % with average value of 13.65% and permeability varies from 0.1 to md. Gas accumulated in Ca1 is of methanenitrogen type with no H2S admixture, and contains 81.3% of hydrocarbons (80.5% CH4) and 18.1% of nitrogen. The development of Ca2 formation is much more differentiated. It is as series of separated m thick rock bodies which porosity varies from almost 0 at the bottom to 30% at the top where the rock is cavernous and fractured. The gas saturation varies from 70 to 96%. Every rock body contains gas of different composition. The gas contains 11.6 to 61.6 % of hydrocarbons ( % of CH4) and 36.2 to 86.9% of nitrogen with H2S admixture of 0.48 to 1.13%. The total recoverable reserves are estimated as BCM ( BCF) of gas 11 BCM (388 BCF) of which are accumulated in Kościan field. In 1999 year the utilization project for the Kościan field has been constructed. The main bulk client for the gas are power plant in Zielona Góra, low methane grid system and local consumers. In 3-4 years new gas production utility Kościan-Brońsko should produce 1.5 BCM of gas. Kościan gas production facility In January 2002 started production at a new facility constructed on Kościan field (Fig. 7). In the first stage production is performed from 4 of 15 wells. Gas from the Kościan field contains some amounts of water which is removed by ethylene glycol

5 (TEG/DEG) working in closed circulation. Water from gas dehydration is pressed into the field, and glycol regenerated. Dry gas is pressed into mercury removal system and than sold to the system. The production will be successively extended onto next wells. In 3-4 years gas production utility should produce 1.5 BCM of gas yearly. At the beginning the accumulation in Ca1 will be exploited. The utilization of accumulations in Ca2 reservoir because of technical reasons is possible after depletion of Ca1 reservoir which is planned no earlier than 2030 (Fig. 8). 2. Comparison of Classifications 2.1 Oil and Gas Field Barnówko-Mostno-Buszewo (BMB) Oil quantities in-place (in thousand metric tons): Key Number Geology axis in-place (GI) I 0 In-place quantities unclassified I 1 Proved in-place quantities I 2 Explored and delineated in-place quantities I 3 Discovered in-place quantities I 4 Perspective in-place quantities Oil recoverable quantities on (in thousand ton): Key number Ekonomic axis (E) Field project axis (F) Geology axis (G) -10 Produced petroleum Commercial Committed projects Proved geology Contingent commerciality Contingent projects Explored and delineated geology Not commercial Exploration projects Discovered geology Prospective geology 41

6 Gas quantities in-place (in million cubic meters): Key Number Geology axis in-place (GI) I 0 In-place quantities unclassified I 1 Proved in-place quantities I 2 Explored and delineated in-place quantities I 3 Discovered in-place quantities I 4 Perspective in-place quantities Gas recoverable quantities on (in million cubic meters): Key number Ekonomic axis (E) Field project axis (F) Geology axis (G) -10 Produced petroleum Commercial Committed projects Proved geology Contingent commerciality Contingent projects Explored and delineated geology Not commercial Exploration projects Discovered geology Prospective geology 41

7 2.2 Gas Field Kościan S Gas quantities in-place (in million cubic meters): Key Number Geology axis in-place (GI) I 0 In-place quantities unclassified I 1 Proved in-place quantities I 2 Explored and delineated in-place quantities I 3 Discovered in-place quantities I 4 Perspective in-place quantities Gas recoverable quantities on (in million cubic meters): Key number Ekonomic axis (E) Field project axis (F) Geology axis (G) -10 Produced petroleum Commercial Committed projects Proved geology Contingent commerciality Contingent projects Explored and delineated geology Not commercial Exploration projects Discovered geology Prospective geology Conclusions - both classifications have been matched using examples of two hydrocarbon fields in Poland; - there are slight differeences in clessifications; - segments of Polish classification (A, B, C1, C2) can be placed and included into UNFC classification.

8 51 30' 51 30' Gdañsk Russia 17 Szczecin 53 30' Szczecin Germany Gorzów Wielkopolski Poznañ ódÿ Warszawa Belarus 53 30' Stargard Szczeciñski Choszczno Czech Republic Wa³cz Kraków Slovakia Pi³a Ukraine 53 00' Trzcianka Barnówko Mostno Buszewo 53 00' Gorzów Wielkopolski 52 30' Kostrzyñ Szamotu³y Miêdzyrzecz Poznañ 52 30' 52 00' Germany Zielona Góra Koœcian 52 00' Lubsko Nowa Sól Leszno

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12 gas well well in drilling abandoned well gas field reef-type structures gas field in Ca2 prospective structure in Ca2 structure in Ca2

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