Aggregation study of asphaltenes from colombian Castilla crude oil using molecular simulation

Abstract

A molecular simulation model to study the mechanism for asphaltene aggregation is presented. Four species were selected, obtained from structural analysis of asphaltenes from the oil extracted from Castilla oil field, in Colombia. Energetic contributions to the aggregation process for each species were studied, and the solubility parameter was evaluated. Finally, the aggregation process between different species was studied in order to determine the tendency of the molecules towards self-association. Results show that for all species, aggregation state is energetically favorable; also, both Van der Waals interactions and electrostatic forces contribute equally to the aggregation process. It was also found that the molecular structure of the substances has a big influence on the manner in which asphaltenes aggregate. For continental structures, long ramifications cause a physical obstacle for aggregation. On the other hand, the molecular flexibility associated with archipelago structures enables the aggregation with other species, but somehow hinders the process of self-association. The solubility parameter for all four substances was within the range established by literature. RESUMEN:Se presenta un modelo de simulación molecular para estudiar el mecanismo de agregación de asfaltenos. Se seleccionaron cuatro especies, obtenidas a partir de análisis estructurales del petróleo extraído del campo Castilla, en Colombia. Se estudiaron las contribuciones energéticas al proceso de agregación y se calculó el parámetro de solubilidad para cada especie. Finalmente, se estudió el proceso de agregación entre las diferentes especies con el fin de determinar la tendencia de las moléculas hacia la autoasociación. Los resultados muestran que para todas las especies, el estado de agregación es energéticamente favorable, y que tanto las fuerzas de Van der Waals como las fuerzas electrostáticas contribuyen en igual magnitud al proceso de agregación. Se encontró también que la estructura molecular de las moléculas tiene una gran influencia en la manera cómo se agregan los asfaltenos. Para las estructuras continentales, las ramificaciones largas ocasionan un impedimento físico para la agregación. Por otro lado, la flexibilidad asociada a las moléculas tipo archipiélago favorece la agregación con otras especies, pero de alguna manera entorpece la autoasociación. El parámetro de solubilidad para todas las especies se encontró dentro del rango establecido por la literatura.

Deformation and Swelling of Kerogen Matrix in Light Hydrocarbons and Carbon Dioxide

“…To prevent the pore collapse and to create a kerogen matrix with a high porosity (over 10%) we examine three different processes. In two of the methods in addition to kerogen molecules we place, at the beginning of stage 1, inside the simulation box: (i) 12 asphaltene/resin molecules from Collell et al, 64 in the other (ii) 21 immature asphaltene molecules from Leoń-Barreneche et al 92 The asphaltene/resin and asphaltene molecules are used to fill the small pores to keep the large pores intact at the end of the MD relaxation process. The pore system collapses in these two methods.…”

Asphaltene Mesoscale Aggregation Behavior in Organic Solvents—A Brownian Dynamics Study

“…Although crude oils may be single-phase under reservoir conditions, depressurization upon production or solvent injection (particularly in heavy oil reservoirs) often induces precipitation and flocculation of asphaltenes out of the crude oil, which may deposit either in the rock pores leading to significant reduction in the productivity of the reservoir because of reduction in the porosity and permeability of the formation rock or in the wellbores, pipelines, and surface facilities, causing the fluid flow to be notably restricted. , For this reason, asphaltene science has received significant attention in recent years to shed light on the main parameters controlling their stability and to develop predictive models. The existing literature offers tremendous advances in the asphaltene molecular and colloidal properties, − the asphaltene phase behavior, − and the interfacial science of asphaltenes. − …”