بررسی آزمایشگاهی تأثیر غلظت آسفالتین و یون‌های دوظرفیتی محلول در آب بر کشش بین سطحی سیستم هپتول/آب شور

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی نفت و گاز، دانشگاه صنعتی سهند، تبریز، ایران

چکیده

کشش بین‌سطحی یکی از مهم‌ترین پارامترهایی است که مستقیماً بر نیروهای مویینگی تأثیر می‌گذارد. از این رو، در فرآیند تولید نفت خام از مخازن نقش مهمی دارد. در این پژوهش با استفاده از روش قطره آویزان، اثرات غلظت آسفالتین در شوری‌های مختلف و یون‌های دوظرفیتی محلول در آب بر کشش بین‌سطحی بررسی شده است. فاز نفتی به شکل مخلوطی از تولوئن و نرمال هپتان (هپتول) در نظر گرفته شده و سپس آسفالتین به آن اضافه گردید تا فعالیت سطحی مولکول‌های آسفالتین و تاثیر آن بر کشش بین‌سطحی بررسی شود. آب با غلظت ppm 000/40 به‌عنوان سیال مبنا و غلظت‌های ppm 4000 به‌عنوان آب با شوری کم و ppm 000/80 به‌عنوان آب با شوری بالا تهیه و کشش بین‌سطحی فاز نفتی-فاز آبی اندازه‌گیری شد. نتایج نشان داد که با افزایش آسفالتین تا غلظتی مشخص در دامنه شوری‌های مختلف، کشش بین‌سطحی هپتول/آب شور کاهش پیدا می‌کند. کمترین مقدار کشش بین‌سطحی در شوری‌های مختلف، در آب با شوری ppm 000/40 مشاهده شد که نشان از این دارد که در شوری بهینه‌ای، حداکثر غلظت آسفالتین به سطح تماس هپتول/آب شور مهاجرت کرده و کشش بین‌سطحی را از mN/m 23 به عدد mN/m 16 کاهش داد. همچنین غلظت 5/0% آسفالتین بیانگر غلظت مهم مایسلی شدن مواد فعال سطحی بود که نشان داد که سطح تماس هپتول/ آب شور تقریباً توسط مولکول‌های آسفالتین در غلظت 5/0% اشغال شده است. بنابراین در غلظت‌های بیشتر از این مقدار، کشش بین‌سطحی کاهش نیافت. در بخش آخر نیز اثر یون‌های دو ظرفیتی محلول در آب بررسی شد و نتایج نشان داد که با افزایش یون کلسیم تا 4 برابر، کشش بین‌سطحی هپتول/آب شور به mN/m 15 (حدود 10% کمتر از حالت مبنا) رسید که به نسبت تمامی نمونه‌ها کمترین مقدار بود.
 

کلیدواژه‌ها


عنوان مقاله [English]

Experimental Study on the Effect of Asphaltene Concentration and Water-soluble Divalent Ions on the Interfacial Tension of Heptol/brine System

نویسندگان [English]

  • Amir Mohammadi
  • Mohammad Chahardowli
  • Mohammad Simjoo
Sahand Faculty of Petroleum and Gas Engineering, Sahand University of Technology, Tabriz, Iran
چکیده [English]

Interfacial tension (IFT) is one of the most important parameters that directly affects the capillary forces, which affects oil recovery. This research investigates the effects of asphaltene concentration and water-soluble divalent ions on IFT. A mixture of toluene and n-heptane, which is called heptol, is used as the model oil, and then asphaltene was added into Heptol to study its effect on the surface-active properties of the model oil. Brine in a salinity of sea water (SW) with a concentration of 40,000 ppm was considered as the base aqueous phase. A diluted brine with a concentration of 4000 ppm was prepared as a low salinity water (LSW), and a concentrated 80,000 ppm aqueous solution is considered high salinity water (HSW). Afterwards, the dynamic IFT of the oil phase/aqueous phase interface was measured using the pendant drop method. Results show that with the increase in the asphaltene concentration, IFT of heptol/brine system was decreased. The lowest value of IFT was observed in the salinity of 40,000 ppm. This may show an optimum salinity range to facilitate migration of asphaltene molecules into brine/heptol interface, which led to an IFT reduction from 23 to 16 mN/m. Results indicated that an asphaltene concentration of 0.5% can be was considered as the critical micelle concentration. At the end, the effect of divalent ions, i.e. calcium, magnesium and sulfate ions in the aqueous phase was investigated, and it is shown that the calcium ion has a larger effect on IT reduction compared to the magnesium and sulfate ions.
 

کلیدواژه‌ها [English]

  • Dynamic Interfacial Tension
  • Heptol
  • Asphaltene
  • divalent ions
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