Case Studies Examine Exploitation Strategies for Development of Mature Gas and Oil Fields

Abstract

This article, written by Editorial Manager Adam Wilson, contains highlights of paper OTC 23373, ’Exploitation Strategy in the Development of Mature Gas and Oil Fields: Case Study,’ by Gina Vega Riveros, Reservoir Consultant, and Emad Yehya, Smoothwell Oil Services, prepared for the 2012 Offshore Technology Conference, Houston, 30 April-3 May. The paper has not been peer reviewed. Copyright 2012 Offshore Technology Conference. Reproduced by permission. Two case studies examine the creation of strategies for the development of mature gas/condensate and oil fields. For the gas/condensate field, the integration of geologic, seismic, production, and reservoir data identified new opportunities for drilling. For the oilfield case study, it is clear that the strategy of exploitation can be improved. According to study results, the oil and gas condensate in place have been increased by 9% and 22%, respectively, compared with the official reserves estimates. Gas/Condensate Case Study Geologic Framework. The gas/condensate reservoirs are in the Roble, San Joaquin, and Guario fields, approximately 11 km southwest of Anaco, Venezuela. The geological model in the Guario 3 reservoir allowed for the integration of four reservoirs as a unique hydraulic unit (Fig. 1). Geologically, the study area is within the greater Oficina area, on the south flank of the Eastern Venezuela basin. The Merecure formation is Oligocene to early Miocene and was deposited in a transitional environment, yielding sandstones with good lateral extension. Petrophysics. In Guario 3, ME-G and ME-H sands have an average effective porosity of 14%. Permeability ranges from 20 md to more than 70 md. The water resistivity of 0.1 Ω·m, cementation exponent of 2.00, saturation exponent of 2.00, and shale volume cutoff of 40% were obtained from field data. Both ME-G and ME-H sands showed similar petrophysical properties. Reservoir Properties. The northwest-ern crest of the Guario 3 reservoir is defined as gas/condensate crude. The eastern part contains a volatile zone of medium gravity with a high concentration of paraffin. The integrated static and dynamic models validated the existence of an areal and vertical communication of four reservoirs into a unique reservoir named Guario 3 (G-3). Geochemical Study. To verify vertical and lateral reservoir communication between ME-G and ME-H sands, gas chromatographic correlations of samples from wells in different reservoirs were used to establish a clear vision about fluid communication. Correlations for Predicting Gas/ Condensate Reservoirs. Many empirical correlations have been reviewed in the literature, and they take into account retrograde condensate. The average ranges for applying the correlations and the equations used can be found in the complete paper. Using the correlations, the original gas condensate in place was 1226.84 billion scf, which was considered satisfactory in comparison with the volumetric method of 1267.37 billion scf.