Viscosity reduction of crude oil through structure determination of asphaltene molecule
Asphaltene may be effectively broken into smaller molecules by first elucidating the structure of the asphaltene and then developing a catalyst system based on the elucidated structure. The structure may be determined based on a series of analytical techniques including NMR, FTIR, Raman spectroscopy, XPS, and LDI. The most probable structure is determined using computational methods based on quantum mechanics and classical molecular dynamics and the catalyst system is developed for the most probable structure.
1. A method of catalytically breaking asphaltene macromolecules in a fluid into smaller molecules with a catalyst system, the catalyst system selected based on an elucidated structure of a sample of the asphaltene macromolecules in the fluid, the asphaltene macromolecules having an aromatic core, the method comprising:
(a) collecting the fluid containing the asphaltene;
(b) identifying a target structure of the aromatic core of the asphaltene in the collected fluid by subjecting the fluid to elemental analysis, NMR spectra, Raman spectroscopy and X-ray photoelectron spectroscopy;
(c) estimating the free energy of the target structure using Hartree-Fock;
(d) testing the fluid for the presence of one or more aliphatic groups and one or more functional groups within the asphaltene macromolecules by subjecting the fluid to FTIR, X-ray photoelectron spectroscopy and NMR;
(e) approximating the probability of a molecular structure of the target structure by applying Hartree-Fock to the target structure and then estimating the free energy of the molecular structure;
(f) developing a catalyst system starting with a catalyst inventory wherein the developed catalyst system is capable of breaking the bonds of a most probable molecule; and
(h) breaking down the asphaltene macromolecules into small molecules with the developed catalyst system.
2. The method of claim 1 , wherein the fluid is crude oil.
3. The method of claim 1 , wherein the functional groups are carbonyls, hydroxyls and sulfoxides.
4. The method of claim 3 , wherein the developed catalyst system has a component capable of breaking the bonds of the carbonyl, hydroxyl or sulfoxide functional groups.
5. The method of claim 1 , wherein step (b) further comprises determining the percent carbon, hydrogen, nitrogen, oxygen, sulfur, nickel and vanadium in the asphaltene sample.
6. The method of claim 1 , further comprising, prior to step (c), determining the architecture of the asphaltene sample, wherein the architecture is either rosary, island or a combination thereof.
7. The method of claim 1 , wherein step (b) further comprises determining the presence and quantity of pyridine, pyrrole, sulfoxide and thiophene in the asphaltene sample.
8. The method of claim 7 , wherein the developed catalyst system has a component capable of breaking the bonds of the pyridine, pyrrole, sulfoxide and thiophene.
9. The method of claim 1 , wherein the functional groups in the asphaltene sample are determined in step (b) by x-ray photoelectron spectroscopy.
10. The method of claim 1 , wherein the aromatic core size of the asphaltene sample is determined in step (b) by Raman spectra.
11. The method of claim 1 , wherein step (b) further comprises identifying the chemical bonds in the asphaltene sample from absorption bands using Fourier Transform Infrared analysis.
12. The method of claim 1 , further comprising subjecting the asphaltene sample to elemental analysis.
13. The method of claim 1 , further comprising assessing the aromatic content, aliphatic content and side chain content of the asphaltene sample by solid state nuclear magnetic resonance 1H and 13C (NMR).
14. The method of claim 13 , further comprising, in conjunction with 13C, determining the presence of —CH3, —CH2 and —CH in the asphaltene sample by Distortionless Enhancement by Polarization Transfer.
15. The method of claim 1 , wherein step (b) further comprises determining chains of the asphaltene sample by subjecting the asphaltene sample to heteronuclear single quantum correlation.
16. The method of claim 1 , further comprising determining the molecular weight distribution of the asphaltene sample by subjecting the asphaltene sample to Laser Desorption/Ionization Molecular Weight Determination.
17. A method of catalytically breaking asphaltene macromolecules in a fluid into smaller molecules with a catalyst system, the method comprising:
(a) collecting a fluid sample containing the asphaltene macromolecules, the asphaltene macromolecules having an aromatic core;
(b) identifying one or more target structures of the aromatic core of the asphaltene macromolecules by subjecting the fluid sample to elemental analysis, NMR spectra, Raman spectroscopy and X-ray photoelectron spectroscopy;
(c) determining the free energy of the one or more target structures of the aromatic core using a Hartree-Fock method and identifying oxygen, sulfur and/or nitrogen in the one or more target structures;
(d) identifying the aliphatic and functional groups of the asphaltene sample by subjecting the fluid sample to FTIR, X-ray photoelectron spectroscopy and NMR;
(e) identifying probable molecular structures of the asphaltene macromolecules by geometric optimization analysis using Hartree-Fock and 6-31G* basis set;
(f) selecting a catalyst system from a catalyst inventory capable of breaking the bonds of the asphaltene macromolecules; and
(g) breaking the bonds of the asphaltene macromolecules with the selected catalyst.
18. A method of breaking the chemical bonds of an asphaltene macromolecule with a catalyst system, the method comprising:
(a) collecting a fluid sample containing the asphaltene macromolecule, the asphaltene macromolecule having an aromatic core;
(b) identifying potential structures of the aromatic core of the asphaltene macromolecule by subjecting the fluid sample to elemental analysis, NMR spectra, Raman spectroscopy and X-ray photoelectron spectroscopy;
(c) estimating the free energy of the identified potential structures of the aromatic core of the asphaltene macromolecules using Hartree-Fock; and
(d) identifying the aliphatic and functional groups of the asphaltene macromolecules by subjecting the collected fluid sample to FTIR, X-ray photoelectron spectroscopy and NMR;
(e) identifying potential structures of the asphaltene macromolecules based on the identified potential structures of the aromatic core of step (b) and the identified aliphatic and functional groups of step (d); and
(f) approximating the probability of a molecular structure of the asphaltene macromolecules by applying Hartree-Fock to the identified potential structures of step (e) and determining the free energy of each of the probable molecular structures;
(g) selecting a catalyst system based on the probable structure of step (f) having the lowest free energy; and
(h) breaking down the asphaltene macromolecules into smaller molecules with the selected catalyst.