Managing a field in a fluvial or delta environment is complicated due to the number of reservoir units. Many of these reservoir units are small and cannot justify significant studies. Because the data acquisition is limited at the reservoir level, the focus is on understanding uncertainties through a flexible approach allowing sensitivity studies. The Dacion field in the eastern part of Venezuela is one of such fields. This block contains more than 500 reservoir units with sizes from 200 Mstb and up.

The Dacion field came on production about 50 years ago. In the early years of development more than 300 wells were drilled and production reached a peak of 45000 bbl/D of oil in about 1958. After that the drilling slowed down and the field was operated on a rate maintenance basis. By 1997 the rate had fallen to approximately 11500 bbl/D. In 1998 the reactivation project was commenced by Lasmo Venezuela (ENI) and managed by PDVSA as part of the third Venezuelan licensing round. The project has so far more than tripled the production at takeover.

The planning approach was based on work done by Lasmo (ENI) in gas fields in Indonesia and modified to an oilfield. The basis of the approach is single cell simulation models for each of the individual units linked to a geological model for the definition of wellbore planning and estimation of productivity. This paper presents how this approach was applied in the Dacion block and how this links to reservoir simulation studies and facilities optimisation. Examples of individual reservoir models will be illustrated. The key in applying the simplified approach has been in understanding the fractional flow properties and being able to express these as type functions. The outcome is an approximate and flexible method to support management of fields with numerous small reservoirs.

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