Use of chemical additives for the control of wax formation and to improve flow properties of waxy crude oil is increasingly being adopted by oil industry operators. Most of these additives, such as pour point depressants, wax crystal modifiers or wax inhibitors are synthetic polymeric compounds, with poly acrylates and methacrylates, poly(alkylmaleate-co-α-olefin), poly(styrene-co-alkylmaleamide) and poly(ethylene-co-vinyl acetate) constituting the dominant chemistry. The high specificity of pour point depressant formulations to oil wells and the considerable expense incurred by industry operators on chemical injections continue to increase the interest for the development of better and cheaper chemical solutions to the wax formation problem. The present work reports the application of natural Cashew Nut Shell Liquid (CNSL) as a flow improver for waxy crude oils and its potential as a veritable resource for the development of new pour point depressants for waxy crude oils. CNSL was solvent-extracted from the shells of Cashew Nut (Anacardium Occidentale L.) using a soxhlet extractor. The physico-chemical properties of CNSL were determined. Functional group characterization was carried out by Fourier Transform Infrared Spectroscopy (FTIR). Rheological evaluation of CNSL at temperatures ranging from 10°C to 60°C using a coaxial cylinder rotational viscometer showed Newtonian behavior. Two Niger-Delta waxy crude oils were characterized to determine their API gravity, water content, kinematic and dynamic viscosity, pour point, Wax Appearance Temperature, wax content, asphaltene content and paraffin carbon number distribution. Wax formation in neat and CNSL-dosed crude oil was studied using cross-polarized microscopy. The pour point of a test crude oil dosed with CNSL at 4000ppm was depressed by 6°C. CNSL reduced the viscosity of the two waxy crude oils by 60% and 35% respectively during couette flow at a temperature of 10°C. CNSL can function as a pour point depressant and viscosity reducer for waxy crude oils and holds promise as a renewable chemical feedstock for the production of pour point depressants and other oilfield chemicals.
Paraffinic crude oils are desirable because of their high content of saturated hydrocarbons but may present handling challenges due to crystallization of high molecular weight paraffin at low temperatures. The prediction of wax properties and behavior of waxy crude oil is important in order to adopt appropriate mitigative measures to forestall flow assurance problems associated with wax crystallization and deposition. Accurate predictive models are limited mainly by the sheer complexity of crude oil composition. Result of analysis of saturates, aromatics, resins and asphaltene content of crude oils (SARA) has been used as a simple tool to predict and interpret crude oil properties and behavior but has been found inadequate in predicting wax instability. In this paper, we report on the use of SARA analysis and paraffin distribution data to interpret the wax properties and flow behavior of Niger-Delta crude oils. The crude oil properties determined include wax content, asphaltene and resin content by gravimetry, pour point, wax appearance temperature by cross-polarized microscopy and paraffin carbon number distribution of whole oil and wax precipitate by GC-FID. Asphaltene and resin content were found to influence the oil pour point, while saturates content, paraffin carbon number of crystallizing waxes and wax content control its low-temperature flow properties.
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