In general, Oil Companies need a contract with the government to have legal rights to carry out Exploration and Production (E&P) projects. In this work, we discuss contractual and economic issues in (E&P) sector in Brazil and the dynamics of uncertainties throughout the stages of an E&P project. This study uses Petroleum Resource Management System - PRMS (SPE, et al., 2007) concepts, its reserve categorization and indicators to measure uncertainty in oil and gas projects. First, we analyze complexities resulting from different contractual regimes and their limits – time, area and cumulative production – as well as the impact on the management of Field Development Plans (FDP). Under these limits, not all production and resources are included in the contract, affecting volume amount, property rights and fiscal regime. Time limits affect decisions about the remaining reserves after the end of contract, while area issues occur when reservoirs extend beyond the geographical boundary of an exploratory block. Cumulative production limit appears in the Transfer of Rights Agreement (TRA), which authorized the Brazilian Government to assign 5 billion barrels of oil equivalent to Petrobras in 2010. The National Agency of Petroleum (ANP) promoted technical studies that indicated the recoverable volume in the area of TRA exceeds the limits originally agreed.

In the second part, we use the 12-step integrated decision analysis methodology by Schiozer, et al. (2015) and PRMS reserve indicators to describe the dynamics of uncertainties throughout exploration, development and production phases. Through reservoir simulation and the optimization of a production strategy, we measured the key reserve indicators in different phases of a project. The increment of developed reserves due to the introduction of wells, in the development, and the reclassification of resources, in the management phase, are assessed probabilistically.

The novel information of this work is the use of the PRMS international standard and the 12-step methodology to not only calculate reserves, but also describe the dynamics of uncertainties throughout a Development Project and to qualify complex contractual and economic issues.

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