The first horizontal well was drilled in Hungary in 1989 and thereafter 60 horizontal sections were completed. The 76% of these wells are in the Algyo field, which is the largest HC accumulation in the Pannonian basin. After a 25-year production, the inaccessible hydrocarbons, which are deposited in unreachable parts of the reservoirs, have become producible by using horizontal wells. The target of the reservoir management was to maximise the long-term profit of the field by acceleration of reserves, reduction of gas and water coning, and by effective use of depleted gas reservoirs and existing vertical wells. In this paper we have summarised the reservoir management approach to enhance the value of the field.

In a complex turbidite sandstone reservoir the oil production capacity is doubled by infill drilling of horizontal wells. This has added 5.0 Million bbl of incremental reserves. In a multilayered part of reservoir Algyo-2 W-2, approximately 1.2 Million barrel of by-passed reserves have became producible after 25 year water injection.

By reducing gas and water coning in the reservoirs Csongrad-Del-1and 2, the oil production rates and the efficiency of well utilisation have been increased.

The depleted Maros-1 sandstone reservoir is now used for underground gas storage and existing gas wells were re-entered and completed to achieve higher daily peak rates.

A gas cap exists in the most part of the oil reservoirs. Development of the gas production well pattern started in the early 90’s. By decreasing the number of wells, improving the daily gas production capacity, and speeding up the exploitation of gas cap reserves, the NPV value was maximised.

In all cases, to reduce costs, existing vertical wells were re-entered and so the over all value of the assets was improved.

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