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“Estimulación de Pozos y Recuperación Mejorada Utilizando Enzimas”

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Petroleum Geochemistry

Evaluation of Oil Sample Treated with Enzyme Enhanced Oil Recovery (EEOR) Fluid

WTC-07-000546 Introduction Intertek Westport Technology Center performed a series of experiments on GreenZyme®, a proprietary enzyme fluid. The objective was to verify whether the enzyme fluid in a diluted concentration improves the flow characteristics of the oil sample provided and potentially heavy oil and make an initial determination of the mechanism for any observed improvement. Experimental Program A 10% concentration of GreenZyme® by volume in water was tested on an oil sample.  Prior to testing the light ends in the oil were removed by evaporation. The purpose of the evaporation was to reduce the API gravity and increase the viscosity so the oil would more closely match a target oil for the enzyme fluid. In addition, the evaporation minimized subsequent variations in the sample due to evaporation of light ends that might mimic or mask the action of the enzyme. After evaporation an aliquot of the oil was mixed with diluted enzyme fluid sample. The mixture was hot-rolled for six (6) days to simulate residence at downhole conditions. Aliquots of the sample before and after hot-rolling were tested for viscosity, API gravity, interfacial tension and composition to measure any action of the enzyme fluid. Data and Interpretation The initial oil sample was analyzed for bulk and compositional properties and subjected to evaporation by rotary evaporation and open vessel evaporation.  The post-evaporation oil was analyzed for bulk and compositional properties.  The evaporation process reduced the saturated hydrocarbon in the oil from about 69.9% to about 63.4%. The aromatic and asphaltene components increased by appropriate amounts and the API gravity was reduced from 36.7 to 25.9. An aliquot of the evaporated oil was mixed with the diluted enzyme treatment fluid provided by Jumpstart. The mixture was hot-rolled for six (6) days to simulate downhole conditions during a treatment process.  After six (6) days, the hot-rolled sample was analyzed to determine the effects of the enzyme treatment. The API gravity of the oil was improved slightly by the enzyme/hot rolling process. The difference is small and may indicate a small improvement in producibility by the enzyme.  One possible mechanism for the enzyme treatment to improve oil recovery is to reduce the interfacial tension between the oil and water.  Interfacial tension measurements were performed on evaporated oil/water, evaporated oil/enzyme solution and hot-rolled oil/enzyme solution. The results indicate that the enzyme solution decreases interfacial tension by an order of magnitude compared to water.  The hot-rolled oil did not show a significant difference compared to the evaporated oil.  This suggests that reduction of surface tension may be one mechanism for improved recovery of oil treated with the Jumpstart enzyme fluid. Another possible mechanism for improvement of oil recovery may be the ”breaking up” of larger molecules into smaller molecules. This might be manifested as a reduction in the overall proportion of asphaltenes, or reduction in the amount of wax in the sample. Based on the results of SARA analysis it appears that the relative amount of saturated hydrocarbons was reduced in the sample during the hot-rolling process.  The SARA results indicate that improved recovery is not the result of reduction in asphaltene content. High-resolution gas chromatography was performed on the oil samples to reveal the detailed composition of the hydrocarbons in the oils and enable determination of chemical changes that may have been initiated by the enzyme treatment.  Visual examination of the chromatograms reveals that the pre-evaporation and pre-hot rolling samples contain clearly visible hydrocarbon peaks out to C44.  However, the post-hot rolling sample contains much smaller peaks beyond about C30 and no visible normal hydrocarbon peaks beyond about C37. The observed reduction in high carbon-number paraffins would be consistent with enzyme action that reduces molecular size of the waxes. Wax reduction may be a mechanism for improvement of producibility of oil by the enzyme. Viscosity was measured on the pre-hot rolled and post-hot rolled oils.  The data suggest that the enzyme/hot rolling process produced a significant reduction in viscosity. Conclusions and Recommendations Based on the observed: Small increase in API gravity, Reduction in interfacial tension, Reduction in the waxy components, and Reduction in viscosity. For the enzyme processed oil compared to the unprocessed oil, it appears that the enzyme fluid may improve the producibility of heavy oil.  We recommend further testing for the purpose of: Quantifying and identifying the mechanism(s) for producibility improvement, Identifying optimum conditions and concentrations for enzyme application, and Identifying oil types and subsurface systems that are most favorable for enzyme treatment.
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