An overview of heavy oil properties and its recovery and transportation methods

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 review31357159

Excitonic transitions in GaAs-AlxGa1-xAs multiple quantum wells affected by interface roughness

Time-resolved photoluminescence has been used to study the effects of interface roughness on excitonic transitions in GaAs-AlxGa1-xAs multiple quantum wells. In addition to the luminescence linewidth broadening and Stokes red shift, the interface roughness also strongly affects the dynamic process of optical transitions so that the excitonic transition peak shifts with delay time. However, the heavy-hole exciton transition has red shifts at short delay times and exhibits a turnover at longer delay times. A maximum shift of about 0.1 meV at a delay time of 4 ns was obtained. We have demonstrated that the peak shift is caused by interface roughness in the quantum wells. Furthermore, the decay of the excitonic transition is found to fit a two-exponential form. Based on a model involving interface roughness and two-exponential decay, we calculated the position of the excitonic transition peak as a function of delay time. Our calculations are consistent with experimental results

An overview of heavy oil properties and its recovery and transportation methods

Submitted by Susilene Barbosa da Silva ([email protected]) on 2020-07-09T13:35:58Z No. of bitstreams: 0 Made available in DSpace on 2020-07-09T13:35:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2014 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 31 3 571 590 Document type: Articl

Expression of the hMSH6 mismatch-repair protein in colon cancer and HeLa cells

PRINCIPLES: 10 to 15% of human colon cancers are associated with an inherited or somatic defect of the DNA Mismatch Repair (MMR) system, which has evolved to correct biosynthetic errors such as nucleotide mis-incorporations or misalignments arising during DNA replication in the S phase of the cell-cycle. Although expression of the MMR genes was expected to be cell-cycle dependent, we and others observed that the MMR proteins hMSH2 and hMLH1 are expressed constitutively in proliferating cells. METHODS: In this study we extend our observations to another essential MMR protein, hMSH6. We used immunohistochemistry to evaluate the expression pattern of this protein in human colorectal mucosa and tumours, as well as in synchronised HeLa-S3 cells, in which we analysed its steady-state levels during the cell-cycle. RESULTS: We show that the immunohistochemical pattern of expression of hMSH6 in normal colorectal crypts and in colon cancers differs significantly from that of the other MMR proteins, with a much lower percentage of replicating cells being hMSH6-positive. This implies that hMSH6 could be cell-cycle regulated. In order to test this hypothesis in a model system, we synchronised HeLa-S3 cells with mitotic shake-off and found that the hMSH6 protein was detectable throughout the cell-cycle, but that its steady-state level increased when cells progressed from G1 to S-phase. DISCUSSION: The increase of hMSH6 steadystate level when cells enter S-phase was expected, since MMR acts during DNA replication. However, the overall low level of oscillations of hMSH6 during the cell-cycle in this cellular model apparently does not fit the immunohistochemical phenotype. We believe that this discrepancy is due to the fact that human cell lines proliferate at a much higher rate than normal and neoplastic colorectal cells in vivo