ASPHALTENE STABILITY IN LIGHT ALKANE/CRUDE OIL MIXTURES

Transcription

1 INSERT HOL SPHLTENE STILITY IN LIGHT LKNE/CRUDE OIL MIXTURES LLNOS-PEREZ J.. 1 ; RTEG-DELNGEL S. S. 1 ; PLCIO-PEREZ. 2 ; GONZLEZ-DVIL V. 3, SUREZ- DOMINGUEZ E.J Mexica Istitute of Complex Systems. Tlaxcala o. 111 esq. v. Jalisco, Col. Uidad Nacioal. CP 894 Cd. Madero, Tam. 2. Istituto de Igeiería. UNM. Circuito Escolar s/, Ciudad Uiversitaria, Delegació Coyoacá, México D.F. 3. Geo Estratos, S.. de C.V. calle 7 # Col. Jardí 20 De Noviembre C.P Cd. Madero, Tam. This paper has bee selected for presetatio ad/or publicatio i the proceedigs for the 2013 Heavy Oil Lati merica Coferece & Exhibitio [HOL13]. The authors of this material have bee cleared by all iterested compaies/employers/cliets to authorize dmg:evets (Caada) ic., the cogress producer, to make this material available to the attedees of HOL13 ad other relevat idustry persoel. STRCT The heavier oil fractio correspods to asphaltees. These are isoluble i low molecular weight alkaes such as -heptae, -hexae, but soluble i bezee, carbo disulfide, chloroform ad other orgaochlorie solvets. The study of asphaltees is importat because they vary i compositio ad molecular weight from oe oil field to aother. Uderstadig the behavior ad cotet the asphaltees helps to determie the possibility of precipitatio i the productio lies ad pipes. Some of the macroscopic properties of petroleum such as viscosity deped o the asphaltee cotet. The high cotet of asphaltees i the oil is also reflected i the decrease of PI gravity. Therefore the objective of this research is to study the stability of the asphaltees from a heavy oil mixed with light hydrocarbos such as low molecular weight alkaes to improve some properties such as PI degree, the desity ad viscosity of the oil. RV dispersat produced by GEO ESTRTOS was also added to mixtures to avoid asphaltee precipitatio caused by low molecular weight alkaes. INTRODUCTION sphaltee correspods to crude oil heaviest fractio, they are formed by polyuclear agglomerates, isoluble i low molecular weight alkaes such as -heptae, -hexae, but soluble i bezee, carbo disulfide, chloroform ad other chloriated orgaic solvets. (1,2) sphaltee are foud i petroleum such as colloidal agglomerates, where the resis act as surfactats ad kept (3, 4,5) them suspesio. sphaltee depositio is a well kow problem, maily for their effects durig oil trasport where deposits have bee observed, icreasig refiig operatio, productio costs ad processes. (6.7) Some oil properties like viscosity depeds o asphaltee cotet; high asphaltee cotet i crude is also reflected with a reduced PI gravity. (8,9) It has bee proposed viscosity reducers to improve fluid trasport. Diluets, such as diesel ad kerosee, are also used to improve the properties of a heavy or extra-heavy 1

2 crude oil, however this is a alterative from the petroleum fractioal distillatio, therefore this is ot either cheap or sustaiable solutio. () Furthermore, there is a productio of orgaic fluids i some gas wells that are ot use i the idustry, such as codesable, cosistig of low molecular weight aliphatic hydrocarbos. These hydrocarbos may be a viable optio for petroleum dilutio without affectig treatmet processes ad icreasig the productio of heavy crude. This alterative has ot bee widely aalyzed at preset. The objective of this study was to determie the stability of mixtures of 16 to 23 PI obtaied from a PI crude oil mixed with low molecular weight alkaes codesed from a gas reservoir ad a viscosity bioreducer used as asphaltee stabilizer. sectios aalyzed of the mixtures usig a cofidece level of (P = 0.01). RESULTS ND DISCUSSION The crude oil had a viscosity of 25,000 cp 25 C, desity of 0.99g/cm 3, a asphaltee cotet of 27.0% ad PI for specific gravity. The codesate had a iitial viscosity of cp@ 25 C, desity of 0.68 g/cm 3, asphaltee cotet <0.1% ad 76 PI. The codesate ifrared spectrum shows sigals of the iteractio ow of a alkae betwee CH as a C6 ad C9 (Figure 2). METHODS For all mixtures it was used as basis a heavy crude oil from the orth of Mexico. The specific gravity was determied uder STM-D287, desity uder STM D5002 ad viscosity uder STM-D6560. We obtaied codesate samples from a ot producig well, but that provides gas, located i the state of Sa Luis Potosi, Mexico. For codesate it was performed a ifrared spectroscopy aalysis ad viscosity, specific gravity ad desity were determied. Mixtures of oil ad codesate were prepared accordig to figure 1 addig RV i two cases, used as asphaltee stabilizer, PI gravity ad viscosity were determied from the orms above. For 30 days cotet of asphaltee, i top ad bottom of the mixture, was moitored. Mixtures M1 - Crude 85% + 15% codesate 0% RV M2 - Crude 85% + 15% codesate 2% RV M3 - Crude 85% + 15% codesate 3% RV M4 - Crude 70% + 30% codesate 0% RV M5 - Crude 70% + 30% de codesate 2% RV M6 - Crude 70% + 30% de codesate 3% RV Figure 1. Descriptio about the prepared mixtures Mixtures were allowed to stad i a chamber at 30 C i a system at atmospheric pressure. Figure 2. Codesate ifrared spectrum. We foud that this liquid should be a straight chai alkae based o the absorptio bads observed. We also made a fractioal distillatio from wich we foud a boilig poit rage from 5 to 118 C. The mixture desity was calculated theoretically usig the desity of oil ad codesate (Equatio 1) x (1) m m is the mixture desity i (g/cm 3 ), is the desity of elemet i (g/cm 3 ) ad x is the fractio o mass of elemet. To kow the PI was substituted the results obtaied i equatio 1 i equatio 2. (11) PIGravity (2) m sphaltee cotet i the upper ad lower sectio of mixtures were aalyzed statistically through aalysis of variace to kow if sigificat differeces exist betwee the 2

3 PI Viscosity (cp) PI Viscosity of the mixtures was theoretically calculated usig the Lederer equatio. (12) l x l x l (3) x V V V (4) Without RV 2% RV 3% RV x 1 (5) x where is viscosity of mixtures (cp), x fractio o mass of elemet, viscosity of elemet (cp), while x correspod to fractio o mass of elemet ad their viscosity (cp); α is a empiric costat, V is a volume of elemet ad V is the volume of elemet, ased o theoretical results show i Figure 3 we decided to prepare mixtures with 15% ad 30% codesate because with these percetages we ca obtai 16 PI ad 22 PI respectively; those specific gravities values are usually required i petroleum storage ceters located i Ciudad Madero, Tamaulipas. The aalysis results of some variable i the mixtures are located i figure 3 too % Light lkae Figure 4. Shows the PI i the mixtures o-dosed ad dosed at differet cocetratio of RV. The results of viscosity for mixtures are show i figure 5. It was foud that the presece of RV causes a decrease i viscosity i bleds of crude PI Teoric PI Experimetal Teoric Without RV 2% RV 3% RV % Light lkae % Light lkae Figure 3. Relatios betwee theoretical PI ad experimetal for differet mixtures of crude-codesate Figure 4 show the PI from o-dosed mixtures ad differet doses of RV for differet alkae cocetratios. It ca be see that mixtures with RV show a improvemet of 5% specific gravity compare with samples without RV. Figure 5. The viscosity results obtaied for differet ratios of codesate to differet RV s dosages. The theoretical results were obtaied from the Lederer equatio. Figure 5 shows the values obtaied for the viscosity of the mixtures, which were dosed with RV. They have a 3

4 evaporated alkae (g) % sphaltee viscosity value 50.9±0.5% below of the samples without dosage ad a 88.0±0.5% below of the theoretical value. For results of the asphaltee determiatio of mixtures it was allowed to stad for 30 days. This time was chose because of that time is higher tha the time residece i taks storage. I this period of time o differeces were foud betwee the upper ad lower level of all mixtures; the error associated with the determiatio was 1%. Values of asphaltee percet are show i Figure 6 ad 7 we ca assume that both the top ad bottom are idetical. Figure 8 show the results of the asphaltee cotet i the mixtures over time. Week 0% RV 2% RV 3% RV Sup If Sup If Sup If S S S S S Figure 6. Ratio of the percetage of asphaltee i the top ad bottom of the mixtures with 15% codesate Week 0% RV 2% RV 3% RV Sup If Sup If Sup If S S S S S Figure 7. Ratio of the percetage of asphaltee i the top ad bottom of the bleds with 30% codesate 17,5 17,0 16,5 16,0 15,5 15,0 14,5 14,0 13,5 13,0 12,5 12,0 11,5 11,0,5,0 9, time (week) Figure 8. sphaltee behavior over time i stad mixtures M1 M2 M3 M4 M5 M6 Durig the experimet it was observed a mass loss by evaporatio, which was reflected i a overall icrease i asphaltee cotet but still without fid differeces betwee the top ad bottom of the cotaier. I the case of the samples stabilized with RV was observed a lower mass loss due to evaporatio, which was approximately.1% for mistures dosed with 2% RV while for mixtures RV with 3% reductio i the loss mass was 15.5% (Figure 9) % RV 2% RV 3% RV % 5% % 20% 25% 30% Iitial % alkae Figure 9. Mass loss by evaporatio 4

5 CONCLUSION I this work we obtaied two 16 ad 23 PI mixtures for 15 ad 30% of codesate i crude. The results of ifrared spectroscopy showed that the codesate is maily composed of low molecular weight alkaes amog C6- C9. I the aalyzed mixtures were foud there are o phase separatios due to precipitatio of asphaltees. y usig RV as a stabilizer we foud a lower viscosity tha the bleds without this product i a 80.0±0.05%. 8. Rogel, E., Leó, O., Espidel, Y., & Gozalez, Y. (2001). sphaltee stability i crude oils. Old Productio & Facilities, 16(2), Sirota, E.., & Li, M. Y. (2007). Physical behavior of asphaltees. Eergy & Fuels, 21(5), Perry, R. H., Gree, D. W., & Maloey, J. O. (2008). Perry's chemical egieers' hadbook (Vol. 7). New York: McGraw-Hill. 11. Lederer, E. L. (1933). Viscosity of mixtures with ad without diluets. I Proc. World Cogress, Lodo (Vol. 2, pp ). It was foud that at ormal temperatures ad pressures evaporatio codesate exists durig experimet, but o asphaltee sigificat differeces were observed betwee the top ad bottom of the cotaiers. Whe RV is used we observed up to a 15.5% reductio i the evaporatio of codesate. NOMENCLTURE V Desity Viscosity Volume Empiric costat REFERENCES 1. Riazi, M. R. (2005). Characterizatio ad properties of petroleum fractios. West Coshohocke, P: STM iteratioal. 2. Tissot,. P. (81). Welte. DH (1984)." Petroleum Formatio ad Occurrece,". 3. all, R., & Joes, J. C. (2009). Thermodyamics of the depositio of complex waxes ad asphaltees i crude oil. Ope Thermodyamics Joural, 3, Evdokimov, I. N. (20). The importace of asphaltee cotet i petroleum II Multi-peak viscosity correlatios. Petroleum Sciece ad Techology, 28(9), Frigerio, F. (2009, December). Naoaggregatio ad solubility of crude oil asphaltees from molecular dyamics simulatios. I C.. ulucea, V. Mladeov, E. Pop, M. Leba, & N. Mastorakis (Eds.), WSES Iteratioal Coferece. Proceedigs. Recet dvaces i iology ad iomedicie (No. 5). WSES. 6. Sirota, E.. (2005). Physical structure of asphaltees. Eergy & fuels, 19(4), irdi, K.. S. (2009). Hadbook of surface ad colloid chemistry. CRC Press. 5