Marginal fields based upon complex reservoirs present to the operating companies real challenges in terms of the implementation of viable full field development plans (FFDP). Small NPVs imply a constant and tight costs control and a careful balance between the data gathering cost and the value of the information that can be retrieved from that data. The fields under analysis are located in the onshore Potiguar Basin, NE Brazil. Productive reservoirs are composed by shallow interbedded sandstone channels and fine shale laminations with complex geometry. Seismic imaging has very poor quality and petrophysical interpretation presents a major challenge due to the presence of fresh formation water. The absence of strong aquifers associated with low initial reservoir pressures and a negligible GOR led to the use of artificial lift and, in a near future, the implementation of a water injection scheme. The oil is paraffinic with low pour point temperatures, which easily creates conditions for high deposition of paraffins. All these factors induce very low productivities, ranging from 100 to 300 bbld with high water cuts. An out of the box thinking attitude was fundamental for Partex to be able to design and implement a sound FFDP, which included the building of consistent static and dynamic models, where uncertainties were identified and quantified. Uncertainty reduction was tackled both through planified but limited data gathering campaigns and compilation of existing analogue data. Operational cost reduction without compromising HSE standards was implemented through innovative well drilling and design and a phased development scheme associated with long term testing (early production schemes).
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