Curve-fitting variants to model Brazil's crude oil offshore post-salt production

Abstract

This study estimates oil production curves applying single and multi-cycle Hubbert models and Hubbert variants for the case of Brazil. The application of a top-down modeling approach is necessary, as the size of oil fields discoveries is usually confidential data and therefore not disclosed in Brazil. Despite fragilities of curve fitting methodologies, this approach therefore continues being widely used, due to its simplicity and relatively low data requirement. The classic Hubbert methodology was improved in this study by considering the asymmetry of production. Additionally, a hybrid model considering techno-economic aspects explains the deviation of the crude oil production rate from the prediction of the Hubbert curve by means of regression analysis. This analysis indicates that the deviation of the crude oil production rate from the Hubbert curve follows, with a four-to five-year lag, changes in oil price. The findings show that the URR of Brazil's post-salt offshore basins hover between 15 and 21 billion barrels of oil. An annual average growth rate of 8% in the pre-salt oil fields can compensate for the decline in post-salt offshore oil production for the period 2016-2025. Error and URR estimates stabilize after peak production for single and multi-cycle Hubbert curves, though the single cycle model proved to be more unstable before peak production than the multi-cycle models.