Advanced strategies for mitigation of asphaltene deposition

Transcription

1 Department of Chemical and Biomolecular Engineering Advanced strategies for mitigation of asphaltene deposition Francisco Paco Vargas * fvargas@rice.edu 8 vargas.rice.edu

2 Background v v v ü Polydisperse mixture of the heaviest and most polarizable fraction of the oil Defined in terms of its solubility Miscible in aromatic solvents, but insoluble in light paraffin solvents Deposition mechanism and molecular structure are not completely understood v Behavior depends strongly on P, T and {x i } (a) n-c 5 asphaltenes (b) n-c 7 asphaltenes J. Buckley, NMT ~mansoori/ Asphaltene.Molecule_html 2

3 Asphaltene Deposition Prediction PRECIPITATION is a necessary but NOT a sufficient condition for DEPOSITION

4 Background (continued) Stable B D C A Reservoir Pressure Reservoir [A] C AOP Unstable D BP VLLE Wellhead [B] Temperature Q. Ge, Y.F. Yap, F.M. Vargas, M. Zhang & J. Chai. 9 th ICHTFMT, Malta

5 Determination of Asphaltene Onset Pressure NIR Spectroscopy Constant T and Composition 5

6 Determination of Asphaltene Onset Pressure NIR Spectroscopy + HPM Constant T and Composition

7 Advanced EOS Modeling On the Prediction of Asphaltene Precipitation Case Study: Fluid B1, Comparison SRK Vs PC-SAFT Pressure, psia 10,000 8,000 6,000 4,000 2, % 30% gas (fit) (prediction) PC-SAFT SRK+P Temperature, F 7

8 Advanced EOS Modeling Modeling using PC-SAFT 10, % gas + 10% gas 8,000 fitted predicted Case Study: Fluid B Pressure, psia Pressure, psia 6,000 4,000 2,000-10,000 8,000 6,000 4, % gas predicted + 30% gas predicted 2, Temperature, F Temperature, F

9 Asphaltene Deposition Prevention A GAME CHANGER is REQUIRED

10 Asphaltene Inhibitors Current testing procedures to assess the performance of asphaltene inhibitors ADT HPHT - SDS Ambient conditions 10

11 SEM image of Asphaltene Aggregate Asphaltene Microstructure (SEM) 5 µm

12 Effect of Dispersants on Asphaltene Aggregation and Precipitation Direct Method Indirect Method Normalized Light intensity Heptane Concentration / (vol. %) vol. % Precipitation onset with inhibitor 30 Crude Oil S vol. % Precipitation onset without inhibitor Disp ppm 25 C 24h Crude OIl Concentration / (vol. %) 0 Normalized Light intensity Heptane Concentration / (vol. %) Crude Oil S 20 Crude Oil Concentration / (vol. %) 10 Disp ppm 25C 24h Precipitation onset with and without inhibitor 0 12

13 Effect of Dispersants Dosage on Asphaltene Aggregation Low Dosage High Dosage Heptane Concentration / (vol. %) Heptane Concentration / (vol. %) E E Normalized Light intensity 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 Blank 25 C 1h Disp 8 70ppm 25 C 1h Disp 9 70ppm 25 C 1h Disp 15 70ppm 25 C 1h Normalized Light intensity 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 Blank 25 C 1h Disp 8 500ppm 25 C 1h Disp 9 500ppm 25 C 1h Disp ppm 25 C 1h 1.E Crude OIl Concentration / (vol. %) 1.E Crude OIl Concentration / (vol. %) 13

14 Asphaltene Dispersants - Efficiency!"#=%&& (% *+,-!./ / *+,- 96-8: ) Heptane Concentration / (vol. %) Heptane Concentration / (vol. %) E E Normalized Light intensity 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 Blank 25 C 1h Disp 8 70ppm 25 C 1h Normalized Light intensity 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 Blank 25 C 1h 1.E Crude OIl Concentration / (vol. %) 1.E Crude OIl Concentration / (vol. %) 14

15 Asphaltene deposition in micromodels Blank In08 Deposition as a function of Inhibitor Concentration However.

16 Probing Asphaltene Deposition Inhibition Using Micromodels Flow rate : 60 µl/min Flow time Commercial Inhibitor concentration 0 ppm 500 ppm 10 min 23 min

17 Novel system to probe asphaltene deposition Syringe pump Crude oil or model oil PTFE Column Effluent Syringe pump Precipitant Ultrasonic water bath 17

18 Effect of Dispersants Dosage on Asphaltene Aggregation Low Dosage High Dosage Heptane Concentration / (vol. %) Heptane Concentration / (vol. %) E E Normalized Light intensity 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 Blank 25 C 1h Disp 8 70ppm 25 C 1h Disp 9 70ppm 25 C 1h Disp 15 70ppm 25 C 1h Normalized Light intensity 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 Blank 25 C 1h Disp 8 500ppm 25 C 1h Disp 9 500ppm 25 C 1h Disp ppm 25 C 1h 1.E Crude OIl Concentration / (vol. %) 1.E Crude OIl Concentration / (vol. %) 18

19 Asphaltene Deposition Effect of Chemicals Amount of Deposited Asphaltenes Vs Dispersive Performance 140 Asphaltene Deposit (mg) y = x R² = Blank Disp 8 Disp 9 Disp 15 Linear (Series3) Dispersive Performance - Efficiency DPE (%) Crude Oil S treated with three commercial asphaltene dispersants 19

20 Mechanism for Asphaltene Deposition

21 Effect of Corrosion on Asphaltene Deposition Ø Corrosion results in the formation of rust on pipeline walls and the variation of surface roughness Ø Study the effect of rust attaching on metallic surfaces on asphaltene deposition Ø Investigate the effect of surface roughness on asphaltene deposition (a) (b) (c) 1000 µm 100 µm (b) 1000 µm 100 µm 1000 µm 100 µm (a) Original sphere (b) Corroded sphere (with rust) (c) Sphere with higher surface roughness(without rust) * Images were taken by using HIROX KH8700 3D Digital Microscope 21

22 Fe(III)-induced asphaltene deposition Deposited asphaltenes, % of total infused asphaltenes Without emulsified water With emulsified water Effect of water 23.4 ± ± 1.5 Without Fe(III) With Fe (III) Effect of Fe (III) 24.9 ± ± 1.4 Without EDTA With EDTA Effect of EDTA 36.2 ± ± 0.5 Although EDTA reduced asphaltene deposition on carbon steel, it increased deposition on PTFE by 170%.

23 Asphaltene Deposition Remediation Best Practices of Deposit Removal using Solvents

24 Asphaltene Deposition Removal Using solvent wash Good Solvent Poor Solvent followed by Good Solvent Immediate Treatment Treatment after 6 days Experiments by Nate Lin & Lisa Biswal Rice University 24

25 Asphaltene Deposition Removal Before washing Washed with poor solvent After 67%heptane and 33% toluene washed (Poor solvent) Experiments by Nate Lin & Lisa Biswal Rice University 25

26 Take-home ideas Asphaltene precipitation is a fully reversible process. Deposition and aging might not be. Asphaltene precipitation is a necessary but not a sufficient condition for deposition (which is the actual problem in oil wellbore). Current experimental techniques (NIR and HPM) are not sensitive enough to detect the true onset of asphaltene precipitation. PC-SAFT is an excellent model to predict the precipitation of asphaltene and design and validate HPHT experiments not so easy to use, though.

27 Take-home ideas (continued) Selection of Asphaltene Deposition Inhibitors is not a trivial task: Chemicals might make the problem WORSE. Most of the current commercial chemical tests are done under unrealistic conditions. New generation of inhibitors must be based on other mechanisms Dispersion might not be the way to go. Surface roughness and iron ions produced by corrosion increase asphaltene deposition. EDTA can reduce asphaltene deposition on metal surfaces but increase deposition on PTFE coatings. When removing asphaltene deposits using solvent wash, the right solvent must be used from the beginning.

28 Department of Chemical and Biomolecular Engineering Advanced strategies for mitigation of asphaltene deposition Francisco Paco Vargas * fvargas@rice.edu 8 vargas.rice.edu