Performance Evaluation of Cashew Nut Shell Liquid CNSL as Flow Improver for Waxy Crude Oils

Abstract

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.