Lante Carbognani

THE EFFECT OF PARAFFINIC FRACTIONS ON CRUDE OIL WAX CRYSTALLIZATION

The influence of the concentration and type of paraffinic crude oil components on the wax appearance temperature (WAT) was evaluated by means of Polarized Light Microscopy. High pour point waxy crudes were doped with paraffin distillation cuts, and changes on cloud points permitted to assess the inefficiency of a polymeric commercial paraffin inhibitor for crudes rich in heavy paraffins. An insensitive crude oil upon the addition of wax inhibitors was fractionated into its hydrocarbon type fractions. Light components were distilled out as the C24 − constituents. C24 + cyclo/iso and linear paraffins were isolated from the distillation residue s saturates by means of 5 Å molecular sieves adduction. The effect of virgin crude oil enrichment with the cyclo/isoparaffins fraction on its cloud point and a polymeric paraffin inhibitor efficiency were evaluated. These components have no significant impact on the inhibitors efficiency at concentrations below 40 wt%, but they increase the crude oil cloud point above 50 wt%, as a consequence of the higher average molecular weight introduced by these components. At this high concentration, a crystal modifier activity enhancement was observed, probably caused by steric hindrance of naphthenic and branched structures. The linear paraffin fraction with more than 24 carbon atoms (nC24+), also isolated from the virgin crude oil, was used for doping experiments on reconstituted crude samples, containing all the original components except this particular fraction. A direct dependence between the cloud point and the concentration of this fraction was assessed.

PARAFFIN DEPOSITION IN OIL PRODUCTION. OIL COMPOSITION AND PARAFFIN INHIBITORS ACTIVITY

ABSTRACT Several commercial paraffin inhibitors were evaluated with highly paraffinic crudes. Pour point depression was observed in some of the studied crudes in the presence of any product, while others showed insignificant changes in this parameter. Crudes characterization was achieved with physico-chemical analysis (pour point, cloud point and API gravity) and hydrocarbon analysis (thin layer chromatography with flame ionization detection, wax content, gel permeation chromatography and high temperature simulated distillation). A correlation between crude oil composition and paraffin inhibitors activity was found. The normal / cyclo+iso-paraffins ratio of the crudes that were not affected by the paraffin inhibitors was found higher compared to the others. The molecular weight distribution of the crudes which responded to modifiers, showed a bimodal character and a concentration of components with more than 24 carbon atoms lower than 39 % wt. On the other hand, the crudes insensitive to the action of the...

Molecular Weight Determination of Asphaltenes from Colombian Crudes by Size Exclusion Chromatography (SEC) and Vapor Pressure Osmometry (VPO)

Abstract Characterization of Colombian asphaltenes isolated from feedstocks to refining units was carried out during this study, emphasizing the determination of their average molecular weights (MW). Experimental conditions used for vapor pressure osmometry (VPO) and size exclusion chromatography (SEC) were investigated aiming to select the most suitable set up that affords the best representative values. SEC was observed to provide the most reasonable MW values, after analysis improvements were achieved by using realistic calibration curves got with phthalocyanines, compounds that closely mimic component structures within oil and asphaltenes fractions. MWs displayed by Colombian vacuum residua asphaltenes fall within the range 1,700 ± 200 Daltons, reported previously for asphaltenes from different reservoirs worldwide.

PREPARATIVE COMPOUND CLASS SEPARATION OF HEAVY OIL VACUUM RESIDUA BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

ABSTRACT An HPLC system is used to separate deasphalted vacuum resids of heavy oils, into saturates, aromatics and two types of resins at preparative scale. The separation is achieved using two silica and one cyano bonded silica columns, and cyclopentane, a mixture of chloroform-methanol and dichleramethane as solvents. Automated repetitive injection is required. Recoveries of the sample are around 100%.

Reliable Determination of Any Water Content of Bitumen and Vacuum Residua. Applications and Validation by Comparison with Known Methodologies

The present study shows how water analysis of bitumen samples produced during in situ combustion or solvent/steam laboratory core flooding experiments is a requisite for a comprehensive understanding of the studied processes. The conceived tetrahydrofuran based Karl Fischer titration technique from a previous study was validated and found advantageous for the purpose, when compared with known azeotropic distillation or nuclear magnetic resonance methodologies.

Reliable Determination of Water Contents of Bitumen and Vacuum Residua via Coulometric Karl Fischer Titration Using Tetrahydrofuran

Standard methods for water content analysis in crude oil are difficult to apply or even fail for bitumen and residual samples that are routinely enriched in water contents. A fast and simple coulometric Karl Fischer (KF) determination of water contents in heavy oil samples was conceived. Tetrahydrofuran was selected for bringing oil and bitumen samples spanning any water percentages into homogeneous solution. Analysis repeatability was deemed reasonable (less than 1.6% relative standard deviation). Correction factors were found mandatory for getting accurate results, as electrode symmetry overtitration effects were observed to affect the analysis.

Monitoring Bitumen Upgrading, Bitumen Recovery, and Characterization of Core Extracts by Hydrocarbon Group-type SARA Analysis

Abstract Hydrocarbon group-type analyses are presented in this work for characterization of samples related to the Province of Albertas abundant bitumen reserves that demand more effective ways of utilization and valorization. The main objective of the study is the evaluation of thin layer chromatography with flame ionization detection (TLC-FID) for rapid hydrocarbon group-type monitoring of bitumen samples and determination of the feasibility of each method for application with very small sample amounts. TLC-FID is a known technique for hydrocarbon (HC) group-type analysis. Different methods of utilization of TLC-FID are assessed here. The analytical techniques employed and data obtained are presented and compared. HC group types are presented in term of saturates, aromatics, resins, and asphaltenes (SARA). Applications are shown for three types of studies related to bitumen: with respect to ultradispersed catalytic bitumen upgrading; solvent-based enhanced bitumen production (Vapex); and characterization of organic extracts from reservoir cores. Techniques are evaluated and validated for each utilization and the preferred methodology indicated.

Preliminary Insights on the Crude Oil Maturation Effects on Asphaltene Stability and Processing

Abstract Geochemical characterization of crude oils is one important classification and exploration tool within the oil business. One maturation parameter is the ratio of cyclic/open demetallized porphyrins (ratio DPEP types/Ethio types). Chromatographic properties of porphyrinic compounds are briefly reviewed. One high-performance liquid chromatography (HPLC) method was selected for measurement of the DPEP/Ethio parameter. This tool is suited for whole crude oils, vacuum residua, and nonvolatile fractions such as asphaltenes. Exploratory data from heavy, medium, and light crude oils; their vacuum residua; and asphaltenes suggest a correlation between maturity [DPEP/(DPEP + Ethio) parameter] and aspects such as solid deposition and processability during upgrading operations. Results with the studied set of samples will be discussed by considering “Earth” (time under reservoir conditions) as a reactor that steadily converts hydrocarbon mixtures, disproportioning them into two major types: I. light ends, II. molecules with a set of undesirable properties such as extended condensation, loss of alkyl appendages, higher density, higher intermolecular aggregation tendency, and high coking indexes. Examples with Venezuelan crude oils will illustrate these aspects.