Date

2014

Author

Ay, Cansu

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An interest in enhanced oil recovery is increasing due to rising oil prices, rising energy consumption and insufficient oil production from conventional techniques. As an EOR technique, alkaline injection is widely used to recover the trapped oil in pore spaces. In this study,the use of sodium hydroxide (NaOH) solutions as an enhanced oil recovery technique for limestone formations in South East Turkey was investigated. Routine core analyses (porosity, permeability and grain density) and spontaneous imbibition for oil recovery observation were performed on 9 plug samples from ‘C’ field and 7 plug samples from ‘G’ field. Since the reservoir temperature of ‘C’field (105 °C) is greater than the limitations of spontaneous imbibition test (~100 °C), the tests were performed at three different temperatures of 50 °C, 70 °C and 90 °C in order to observe the effect of temperature on the experiments. As the test fluids, crude oil samples and formation water samples taken from the fields,as well as fresh water and NaOH solutions at different concentrations were used. High pressure mercury injection capillary pressure and pore throat size distribution analyses were conducted on 9 of the plug samples used in the imbibition tests for core characterization. Core flooding tests and interfacial tension measurements were performed following the completion of imbibition tests. Both imbibition and core flood test results showed that, the existence of NaOH in the water phase and caused additional oil recovery from the samples and reduced interfacial tension between oil and alkaline solution. 1.0wt% NaOH had the highest total oil recovery 69.8%OOIP in field ‘C’ but if the experiments had equal time intervals for each sample, the highest oil recovery might be given by a higher NaOH concentration. The highest oil recovery was given by 0.2wt% NaOH solution 23%OOIP in field ‘G’. But except 0.2wt%, there was a proportional relationship between NaOH concentration and oil recovery. The results show also that, increase in temperature helps to decrease remaining oil saturation.

Subject Keywords

Enhanced oil recovery., Limestone., Carbonate rocks., Sodium hydroxide., Oil fields

URI

http://etd.lib.metu.edu.tr/upload/12618057/index.pdf
https://hdl.handle.net/11511/24105

Collections

Graduate School of Natural and Applied Sciences, Thesis