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Abstract Hungarian Oil and Gas plc. (MOL) decided to carry out a more than 1000 square km 3D survey over the mature age Szeged-Algyö Field in 1999. Data acquisition and processing were carried out by Geophysical Services Ltd. (GES). This case history shows how MOL and GES cooperated and interacted in planning and managing of this complex 3D project. During the preparation and operation phases of the survey they had to manage several environmental protection and public concerns, while keeping an eye on the geological objectives of the project. The continuous real time information flow and feedback - between the field crew and quality control organizations of the Client and Contractor - could manage the challenging field conditions. Regular field audits and team meetings monitored the required quality and evaluated the process performance. The improved interaction resulted in smooth operation and good quality data satisfying the Client's requests with zero impact on the environment and public interests. Introduction The Szeged-Algyö Field is the largest hydrocarbon accumulation of Hungary. The oil and gas pools were discovered in 1965 and within two years the CH reservoirs were set on pipe. The producing field is located partially underneath the cities Szeged and Algyö having an improved infrastructure and more than 180 000 inhabitants. The field was explored and developed by extensive drilling activity mainly in the 60s and 70s. The annual production of the Szeged-Algyö field at its peak time - in the 70s and early 80s - reached 7.5 MBBL oil and 100 Mcf gas. Although more than 1000 wells were drilled into the reservoirs to date, complex stratification patterns governed by the original lacustrine deltaic depositional environment prevented unambiguous correlation and spatial definition of the sandstone bodies. By the end of the 90s the declining production of the field necessitated exploration of the forecasted small size satellite fields around the main producing field. Planning and Pre- Szeged and Algyö cities, the Tisza and Maros rivers with their protected wetland forests and large permitting fishing lakes located North to Szeged were the main challenges that 3D seismic had to face to (See Fig. 1). During the pre-permitting phase the work program - containing the theoretical 3D network - was submitted to the competent environmental protection organizations and to other local authorities to ask for their preliminary opinion. Besides the strictly protected exclusion zones there were two main temporal restrictions which basically determined the further planning steps: BLOCK 1 - - FORUM 6 561 LARGE SCALE 3D SEISMIC DATA ACQUISITION ON AN ENVIRONMENTALLY SENSITIVE AREA IN CENTRAL EUROPE because of the spring time breeding season and passage of bird
Abstract In Hungary, the oil prices in the range of $20 makes EOR projects commercially viable. Because of their structures and fluid properties, the oil reservoirs in Hungary are suitable for gas injection EOR methods. This EOR potential is well supported by favourable infrastructure in the local oil industry/surroundings. The paper presents the EOR application for a large reservoir in the Pannonian basin. The Szeged-Móraváros is undersaturated fractured reservoir with Triassic dolomite, Miocene sandstone and conglomerate at the depth of 2630–2450 meters below the sea level. The OOIP derived from material balance is 11.56 million cubic meter and oil gravity is 817 kg/m3. The initial pressure was pr=331 bar, initial temperature was tr=140 °C. In the period of the natural depletion between 1975–1980, the cumulative oil production was 1,27 million cubic meter. In this period, because of the limited water influx, the reservoir pressure dropped below the bubble point and secondary gas cap started to increase. The pressure dropped to pr=244 bar. In 1980, water injection was started to maintain the reservoir pressure. The aim was to increase the reservoir pressure above the bubble point pressure. With this water injection from 1980 to the present time, the oil recovery is 36.4 % with a cumulative oil production of 4.21 million cubic meter. The current reservoir pressure is 250 bar. For studying the further recovery enhancement, laboratory and reservoir simulation studies were carried out to evaluate different gases. Natural gas, nitrogen, and CO2 were selected for the gas injection near the structure top. In Hungary, large CO2 reserves are available 50–250 km distance from the oil field. The natural gas resources are easily available because of the developed gas distribution network and the production of nitrogen by stripping from the air can be also easily realised. At the optimal pr=250 bar pressure, the displacement process is not miscible in the reservoir, and the recovery increment is not sensitive to the type of injected gas or its quality. The reservoir simulation shows the recovery increment is about 12 %. We have selected nitrogen gas as an injection gas based upon economic and environment evaluations. The paper describes how we arrived at this conclusion in a country where there is a well-developed natural gas market. The paper also includes discussion about the methods and criteria used to select the process. Introduction The amount of the produced oil and condensate coming from the EOR processes is 170,4 thousand tons recently. More than 70 % of the total amount is connected to gas injection technologies mainly to CO2 injection but methane and ethane rich gases are also used as the material of EOR injection mass. CO2 is available from natural resources in the Western part of the country, here is the largest CO2 injection project is taking part. In the central area of the country, only limited natural CO2 resources are available. Here a gas enriching plant is working where the CO2 is forming as a sideproduct. CO2 reservoirs are also in the eastern part of the country but their development has not yet begun because of the lack of utilisation. However the most important oil resources of the country are in the Southern, Southern-East areas relatively far from the above mentioned CO2 areas. Therefore, in this region, studying the possibility of methane and nitrogen injection is necessary because of the limited or cost requiring availability of CO2. A systematic screening was made between 1997–2000 for the Southern-Hungarian oilfields. The most important conclusion of the study was that the temperature and pressure conditions, the geological features and the PVT characteristics of the reservoir fluids are favourable mainly for the EOR with gas injection.