No 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.

Oil extracts of Ukpeliede spill samples from Niger Delta (Nigeria) were analyzed by gas chromatography. The amount of polycyclic aromatic hydrocarbons (PAHs), especially the lower-molecular-weight naphthene, fluorine, phenathrene, pyrene, and benzo[a]anthracene, decreased within the sampling intervals of 2 months and 5 months. There was a predominance of three-to-six-ring PAHs over the two-ring PAHs. There was marked disappearance of n-C8 to n-C11 hydrocarbon fractions and the acyclic isoprenoids (pristane and phytane). The depletion of these molecules within the two sampling intervals suggests the possible attenuation of hydrocarbons as a result of the environmental modification within the set interval.

Sandy soil samples spiked with Bonny light crude oil were subsequently treated with Fenton's reagent at acidic, neutral, and basic pH ranges. Oil extracts from these samples including an untreated one were analyzed 1 week later with a gas chromatograph to provide evidence of hydrocarbon depletion by the oxidant. The reduction of three broad hydrocarbon groups-total petroleum hydrocarbon (TPH); benzene, toluene, ethylbenzene, and xylene (BTEX); and polycyclic aromatic hydrocarbon (PAH) were investigated at various pHs. Hydrocarbon removal was efficient, with treatment at the acidic pH giving the highest removal of about 96% for PAH, 99% for BTEX, and some TPH components experiencing complete disappearance. The four-ringed PAHs were depleted more than their three-ringed counterparts at the studied pH ranges.

Use of pour point depressants/flow improvers is an effective strategy for alleviation of flow problems associated with wax formation in paraffinic crude oil. Biobased oilfield chemicals derived from renewables are appealing as low-cost, eco-friendly alternatives to conventional pour point depressants. Cashew nut shell liquid (CNSL) extracted from Anacardium occidentale shells was modified by esterification with glycerol. The CNSL derivatives were evaluated as pour point depressants and low-temperature flow improver for waxy crude oil. Pour point and viscosity of doped crude oil were reduced by a maximum of 15 C and 86%, respectively. Cross-polarized micrographs of doped oil were analyzed with Image J software and showed decrease in wax crystal aspect ratio and boundary fractal dimension indicating modifications to wax morphology and microstructure.