Unconventional oils - mainly heavy oils, extra heavy oils and bitumens - represent a significant share of the total oil world reserves. Oil companies have expressed interest in unconventional oil as alternative resources for the energy supply. These resources are composed usually of viscous oils and, for this reason, their use requires additional efforts to guarantee the viability of the oil recovery from the reservoir and its subsequent transportation to production wells and to ports and refineries. This review describes the main properties of high-viscosity crude oils, as well as compares traditional and emergent methods for their recovery and transportation. The main characteristics of viscous oils are discussed to highlight the oil properties that affect their flowability in the processes of recovery and pipeline transportation. Chemical composition is the starting point for the oil characterization and it has major impact on other properties, including key properties for their dynamics, such as density and viscosity. Next, enhanced oil recovery (EOR) methods are presented, followed by a discussion about pipeline and transportation methods. In addition, the main challenges to achieve viable recovery and transportation of unconventional oils are compared for the different alternatives proposed. The work is especially focused on the heavy oils, while other hydrocarbon solid sources, such as oil sands and shale oil, are outside of the scope of this review.

In the welding process, the most interesting regions for heat transfer analysis are the fusion zone (FZ) and the heat affected zone (HAZ), where high temperatures are reached. These high temperature levels cause phase transformations and alterations in the mechanical properties of the welded metal. The calculations to estimate the temperature distribution in multiple pass welding is more complex than in the single pass processes, due to superimposed thermal effects of one pass over the previous passes. In the present work, a comparison is made between thermal cycles obtained from analytical models regarding point (concentrated) and Gaussian (distributed) heat sources. The use of distributed heat source prevents infinite temperatures values near the fusion zone. The comparison shows that the thermal cycles obtained from the distributed heat source model are more reliable than those obtained from the concentrated heat source model.