Naphthenic acids represent a subfraction of the crude oil resins that contains predominantly carboxylic acids with saturated cyclic structures and corresponds to a complex mixture of compounds. The naphthenic acids can cause deposition problems. These compounds however also play an important role in some phenomena occurring, and then separation from crude oil would improve oil quality during the production. In this contribution, some aspects of the solution behavior of naphthenic acids are presented. It was observed that these compounds form stable liquid mixtures with organic solvents in a wide range of solubility parameters. When added to partially soluble liquid mixtures, such as n-heptane/methanol, they improve the mutual solubility of these liquids, increasing the solubility domain and partition into both liquid phases. The precipitation onset for asphaltenes dissolved in toluene titrated with n-heptane was increased by the addition of naphthenic acids, indicating that these compounds contribute to the solubilization of asphaltenes representing a “good solvent” for this fraction. Applying the polymer solutions to the asphaltenes dissolved in liquid mixtures, treating the naphthenic acids as pure pseudo-components, and assuming that asphaltenes precipitation onset occurs at a particular solvent composition corresponding to a “critical solubility parameter” value from 20 to 23 MPa1/2 were obtained for the naphthenic acids that are in good agreement to those obtained by differential scanning calorimetry (DSC).

Summary: This work describes a method to evaluate, in reduced scale, the performance of polymer samples as drag reduction agents in aqueous solutions. To measure the pressure drop in a turbulent regime, a specially adapted capillary viscosimeter was used, with reduced dimensions adapted to produce the desired regime and adequate pressure measurement points. To verify the technique's reliability, samples of polyacrylamide were synthesized with different molar masses, by varying the quantity of the polymerization initiator. The molar masses obtained were determined by size exclusion chromatography (SEC). The efficiency of the polymer as a drag reducer, as expected, increased as the molar mass increased, which validates the use of this method to study the drag reduction properties of polymer materials in aqueous solutions.

In Brazil, for the last four decades, Petrobras, a state-owned company, had retained a monopolistic concession for the exploration of Oil & Gas prospects, when, in 1998, the law was changed and a broad range of opportunities were created. Since then, Petrobras has been offering a series of Join Venture opportunities for foreign oil companies to farm in. Presently, a number of international oil companies installed offices locally and started to participate in the upstream sector. ANP, the National Petroleum Agency, is offering for tender various blocks both offshore and onshore. The first bid round was a major success, in mid 1999, the second bid round being scheduled for the third quarter of year 2,000. Blocks leased in the first bid round are now being explored by means of 2D and 3D seismic, and the first exploratory wells will be soon drilled. This article presents a framework to perform an economic evaluation of oil & gas prospects, taking into account the risk factor. The Net Present Value of each block is first computed based upon an average value. Following that, Monte Carlo simulation is used to compute the downside risk. The inputs are determined by means of probability distributions. Reservoir parameters, capital and operating costs and oil prices are fed into the program, revealing the NPV sensitivity to each factor. The problem is further structured by means of decision trees. The Expected Monetary Value, based upon perceived probabilities of success, is estimated, utility functions being used to account for risk aversion. The optimum level of participation in each prospect is determined, using the so-called Certainty Equivalent concept. Finally, the formation of an optimum portfolio is discussed, so that any oil company can establish its strategy in joint bids and farm ins. Four hypothetical prospects are evaluated; with different levels of investment and risk profiles, namely, from higher probability of success to new frontier, lower probability of success. The correspondence with real life may be, respectively, the Campos Basin, where 70% of Brazilian oil production comes from, and basins like Pelotas, where there are no producing wells, with little seismic available. The framework suggested in this work could be useful for any company that is currently involved with exploration activities. Additionally, it may be used for analyzing any investment with a certain degree of uncertainty or volatility.