Modeling Heavy Oils in Aspen HYSYS. Engineering Excellence Webinar Series 26 January 2010

Transcription

1 Modeling Heavy Oils in Aspen HYSYS Engineering Excellence Webinar Series 26 January Aspen Technology, Inc. All rights reserved

2 Modeling Heavy Oils in Aspen HYSYS Dr. Mohammad Khoshkbarchi Senior Project Manager, Process Ecology Sanjeev Mullick Director, Product Marketing, AspenTech Aspen Technology, Inc. All rights reserved 2

3 Agenda Heavy Oil Overview Best Practices for Modeling Heavy Oils in Aspen HYSYS Sample Applications Recommendations and Conclusions Q&A 2010 Aspen Technology, Inc. All rights reserved 3

4 What is Heavy Oil? By definition, has API gravity < 20 & viscosity > 1,000 cp Has over 60 carbon atoms, and hence, a high BP & MW Mainly comprised of hydrocarbons heavier than pentanes, with a high ratio of aromatics and naphthenes to paraffins High amounts of nitrogen, sulfur (~5%), oxygen and heavy metals Exists in a semi-solid state and may not flow in its naturally occurring state 2010 Aspen Technology, Inc. All rights reserved 4

5 Comparative Oil Properties Oil Viscosity: Conventional Crude <~ 30,000 cst Conventional Heavy 30,000 40,000 cst Thermal Heavy 200, ,000 cst Diluent cst Oil API: Conventional Crude Conventional Heavy Extra Heavy (Thermal) Tar Sand > 25 API API API 12 7 API 2010 Aspen Technology, Inc. All rights reserved 5

6 Where Does it Exist? Heavy oil deposits total almost 5½ trillion barrels (est.); 80% of deposits are in the Western Hemisphere - In the U.S., heavy hydrocarbon deposits are estimated to be more than eight times that of the nation's remaining reserves of conventional crude oil 2010 Aspen Technology, Inc. All rights reserved 6

7 Where Does it Exist? 1. Western Canada Mainly in the form of oil sands in Alberta 44% of Canadian oil production in 2007 was from oil sands, with an additional 18% being heavy crude oil Average density is API = 8 Viscosity within a range ,000 cp, and higher (up to 100,000 cp) 2. Venezuela Mainly heavy oil Viscosity within a range of cp 2010 Aspen Technology, Inc. All rights reserved 7

8 Challenges in Modeling Heavy Oils Characterizing the oil Defaults Data Bulk Curves Viscosity Blending to match properties at wellhead Emulsion viscosity Phase entrainment/carryover Foaming Further effects of adding solvents 2010 Aspen Technology, Inc. All rights reserved 8

9 Implications of Poor Modeling Incorrect wellhead conditions Steam-Oil ratio Properties prediction Flash conditions: vapor when it s really a liquid/vice versa, trivial phases Large pressure gradients Unattainable separations Products: SCO Capacity Yields Over/under design of towers, drums Misrepresented utilities Over/under design of heat exchanger units 2010 Aspen Technology, Inc. All rights reserved 9

10 Agenda Heavy Oil Overview Best Practices for Modeling Heavy Oils in Aspen HYSYS Sample Applications Recommendations and Conclusions Q&A 2010 Aspen Technology, Inc. All rights reserved 10

11 Best Practices Workflow Assay Setup Enter Assay lab data Check Correlation set Verify/alter Extrapolation & Conversion Methods Oil Properties Enter User Cutpoint ranges Blend Assay & Cut into Hypos Compare Property Plots Install Oil Build PFD Blend Oil & Water streams Alter emulsion viscosity, if necessary Incorporate entrainment Use Utilities to check products 2010 Aspen Technology, Inc. All rights reserved 11

12 Oil Characterization in Aspen HYSYS Purpose: convert lab analyses Aspen HYSYS library and hypothetical components 3 steps in Oil Characterization: 1. Characterize the Assay 2. Generate Pseudo Components Cut/Blend 3. Install the Oil in the Flowsheet 2010 Aspen Technology, Inc. All rights reserved 12

13 True Boiling Point (TBP) FBP True Boiling Point Curve 1200 Bolining Point (C) IBPi FBPi 200 IBP Alternative Methods: ASTM D86 (atmospheric batch distillation) ASTM D1160 (vacuum batch distillation) ASTM D2887 (chromatography) Usually unsuitable for heavy crudes Volume % Distilled 2010 Aspen Technology, Inc. All rights reserved 13

14 1. Characterizing the Assay Know how your lab handles its analysis: Which analysis type? Are they applying any corrections? Are light-ends included? Or is it a separate analysis? Input Composition Auto Calculate Ignore 2010 Aspen Technology, Inc. All rights reserved 14

15 True Boiling Point (TBP) Conventional Oil TBP Heavy Oil TBP Bolining Point (C) Volume % Distilled Bolining Point (C) Volume % Distilled Heavy oil TBP has much fewer experimental points No FBP or close point to it 2010 Aspen Technology, Inc. All rights reserved 15

16 1. Characterizing the Assay Light Ends handling and Bulk Property fitting: Are Light-ends included in the input curves? Are Light-ends included in the bulk properties? What bulk data do you have? Do you also have property curves? Do you want to control which part of the curve is tuned to match the bulk property? Understand the correlations used Understand which conversion and extrapolation methods are used 2010 Aspen Technology, Inc. All rights reserved 16

17 Best Practices Specify Properties for Heavy Oils Bulk property options include: Molecular Weight > 16 Mass Density = 250 ~ 2000 kg/m 3 Required Watson K Factor = 8 ~ 15 Recommended Bulk 100 F F Required Add other property curves Molecular Weight curve Density curve Recommended Viscosity curve (two curves) Recommended 2010 Aspen Technology, Inc. All rights reserved 17

18 2. Generating Pseudocomponents Blending is used to blend a number of assays. It provides a general presentation of the whole crude. Cutting not only generates the pseudocomponents, but also determines their compositions in the crude Auto Cut: based on values specified internally User Points: specified cut points are proportioned based on internal weighting scheme User Range: specify boiling point ranges and the number of cuts per range 2010 Aspen Technology, Inc. All rights reserved 18

19 Best Practices Creating Hypotheticals for Heavy Oils When generating pseudocomponents for heavy oil fractionation, recommend using User Points or User Defined Ranges How many? Minimum of 4 pseudocomponents per draw Use Composite plot to determine exact number for each temperature range Test accuracy of input assay data against generated hypotheticals How well does my data match with Aspen HYSYS? 2010 Aspen Technology, Inc. All rights reserved 19

20 True Boiling Point (TBP) In the absence of high FBP experimental data the extrapolation of the curve could result in abnormalities. This will have a great impact on the set up of some unit operations such as distillation. The undershoot in the extrapolation could change to overshoot as well Solution: Use a guide point such as FBP or IBP Use other distribution Bolining Point (C) True Boiling Point Curve Volume % Distilled 2010 Aspen Technology, Inc. All rights reserved 20

21 Best Practices Predict Heavy Oil Fractions Use the Distribution Plot to help predict crude products Enter custom cuts to slice oil as desired See product changes with temperature Use these fractions as initial product draw rates for converging the column (i.e., for front end of an upgrader) Approximately how much of every product will I get? 2010 Aspen Technology, Inc. All rights reserved 21

22 3. Installing the Oil Installing the oil in the flowsheet is done by providing a stream name on the Install Oil tab. This: 1. Adds the pseudo components to the Fluid Package 2. Transfers the pseudo component information into the Flowsheet 3. Creates a stream on the Flowsheet with a defined composition If you forget this step, you will not be able to see the oil composition in the flowsheet! 2010 Aspen Technology, Inc. All rights reserved 22

23 Best Practices Stream Utilities for Oils Use stream Utilities to check individual streams against the composite oil Boiling Point Curves: calculates simulated distillation data and critical property data for each cut point and cold properties Cold Properties: shows boiling point curve and breakdown of Paraffins/ Naphthenes/Aromatics for the installed oil 2010 Aspen Technology, Inc. All rights reserved 23

24 Aspen HYSYS Can Accurately Predict Important Heavy Crude Properties The following section looks at special considerations in predicting heavy oil properties, including: Specific Gravity/Standard Density Extrapolation Methods & Fitting Options Viscosity General Oil Properties, i.e., Thermal Conductivity 2010 Aspen Technology, Inc. All rights reserved 24

25 Specific Gravity Specific gravity is an extremely important data point for the accurate extrapolation of heavy oils, as well as an important data point to generate a missing SG curve Bulk SG is, by default, optional and part of the assay analysis It is therefore recommended that the bulk density (or density curve) be supplied as an input parameter for the accurate characterization of a heavy oil 2010 Aspen Technology, Inc. All rights reserved 25

26 Specific Gravity Example Problem and Solution Problem: Range of discrepancy in estimated density values is 6% at lower NBPs and up to 11% at higher NBPs Solution: Apply different correlation sets for multiple NBP ranges Inconsistent/unreliable SGs at heavy ends can result especially if the SG is estimated from any correlation where NBP is the only independent variable, since SG might also be a function of MW The SG curve generated from input data should be consistent and follow the trend of the boiling point curve Watson K method creates a Watson K curve based on boiling curve and average SG. This Watson K curve is used to generate component SG boiling point, then moved up and down to match bulk SG Aspen Technology, Inc. All rights reserved 26

27 Curve Extrapolation Available mathematical extrapolation methods (for both ends) include: Probability Least squares Lagrange Recommended selections for heavy oils are shown here The linear extrapolation method is not appropriate for extrapolating the SG, MW and viscosity curves for heavy ends. The least squares (2nd order polynomial), applied at both ends, is recommended Aspen Technology, Inc. All rights reserved 27

28 Curve Fitting Options For each input curve, can specify: Curve Includes L.E. Bulk Value Bulk Value Incl. L.E. Head % Head Adjust Weight Main % Main Adjust Weight Tail Adjust Weight 2010 Aspen Technology, Inc. All rights reserved 28

29 Curve Fitting Options Example Problem and Solution Problem: Property curves are shifted along y-axis Solution: To correct discrepancies, you have 3 options: Change Bulk Value (least accurate), or Adjust Main % and Tail Adj Wt. to correspond with data entry points (manual), or Apply Smart Bulk Fitting (automatic) 2010 Aspen Technology, Inc. All rights reserved 29

30 Curve Fitting Options Example 2010 Aspen Technology, Inc. All rights reserved 30

31 Curve Fitting Options Example Problem and Solution Problem: TBP Curve is shifted along the liq. vol. x-axis A TBP, by default, includes light ends; however, if the TBP was obtained from a light-ends free sample, Aspen HYSYS can readjust the curve to the overall crude Solution: Choose to fit with or without light ends, as appropriate: In situations when only partial light ends analysis data is available, Aspen HYSYS can generate overlapping hypothetical components to compensate the missing portion of the light ends, making the output stream matching both the partial light ends input and the other input curves 2010 Aspen Technology, Inc. All rights reserved 31

32 Viscosity Viscosity is key to both successfully understanding the fluid properties of a heavy oil and for predicting oil recovery Both viscosity reduction and thermal expansion are the key properties to increase productivity of heavy oils Viscosity influences every aspect of a heavy oil development Effect of viscosity on pressure gradients For real liquids, the effect of pressure is relatively small when compared to the temperature effect; but large pressure gradients tend to occur with high viscosity oils. At higher flow rates, frictional heating effects can become significant, and the heating tends to reduce the oil viscosity, which in turn, affects the pressure gradient. The net result is that the predicted pressure gradient may be higher than should actually be expected Aspen Technology, Inc. All rights reserved 32

33 Viscosity Options in Aspen HYSYS Since viscosity is the key property to proper heavy oils characterization, we do not recommend omitting this variable Optional to use: Bulk viscosity values (recommended) Only viscosity curve Two viscosity curves (optimal) Higher flexibility on temperature extrapolation Note: Bulk viscosity and viscosity curves can be input at different temperatures 2010 Aspen Technology, Inc. All rights reserved 33

34 Heavy Crude Viscosity Trends Full Crude Viscosity vs. Temperature Cut Viscosity vs. Final Boiling Point Viscosity (cst) Viscosity (cst) Temperature (C) FBP (C) Use two points from full crude viscosity curve. High FBP viscosities are usually a result of extrapolation using a log(log) approach Aspen Technology, Inc. All rights reserved 34

35 Viscosity Curves Example Problem and Solution Problem: Calculated and inputted viscosity values don t match. Depending on the application, bulk values are good, but in other cases (like heavy oils) the cuts value (i.e., residue) is better. Quite a typical case: Low quality viscosity curves for extrapolation purposes It is a measure range problem Inconsistent data leads to a mismatch of input to calculated Solution: Manipulate bulk value by trial and error to match residue viscosity 2010 Aspen Technology, Inc. All rights reserved 35

36 Indexed Viscosity Viscosity cannot be blended linearly, so a methodology is adopted that substitutes a function of the measured viscosity that is approximately linear with temperature. A linearized equation for viscosity is given by Twu and Bulls (1980). On the Parameters tab for equation of state methods, you can change the viscosity calculation method from HYSYS Viscosity to Indexed Viscosity to determine the blended liquid viscosity 2010 Aspen Technology, Inc. All rights reserved 36

37 General Oil Properties When comparing Aspen HYSYS-predicted property values against vendor, lab, or plant data, for properties such as liquid density, viscosity, thermal conductivity and heat capacity, there can be some discrepancies, since: They are generated from general thermodynamic models It is not realistic to expect model predicted results to exactly match real data To improve the accuracy of these properties, use the Tabular feature in Aspen HYSYS to: Edit the coefficients for property correlation Regress lab data directly in Aspen HYSYS 2010 Aspen Technology, Inc. All rights reserved 37

38 Example: Improving Thermal Conductivity Alter coefficients Regress data 2010 Aspen Technology, Inc. All rights reserved 38

39 Checklist for Modeling Heavy Oils Enter lab data distillation data, light ends, bulk properties, and/or curve data (MW, density, viscosity) Verify correlation set used for assay over entire temperature range Validate appropriate selections for assay extrapolation and conversion methods Blend and cut assay using user cutpoint ranges Compare plots of input data vs. calculated TBP curve, gravity, viscosities, etc. Install oil 2010 Aspen Technology, Inc. All rights reserved 39

40 Checklist for Modeling Heavy Oils Blend water and oil streams; check emulsion properties Build flowsheet Incorporate phase entrainment in separators (using carryover function) and columns (via efficiencies) Use stream utilities (BP curves, Cold Properties) to check individual streams against the composite oil 2010 Aspen Technology, Inc. All rights reserved 40

41 Agenda Heavy Oil Overview Best Practices for Modeling Heavy Oils in Aspen HYSYS Sample Applications Recommendations and Conclusions Q&A 2010 Aspen Technology, Inc. All rights reserved 41

42 Steam Assisted Gravity Drainage (SAGD) DILUENT/ SYNTHETIC CRUDE RECOVERED DILUENT/SCO Gas Treating SOUR GASES GAS SWEET GASES Well Pad Emulsion Gas-Oil- Water Separation OIL [DILBIT/ SYNBIT] To Upgrader or Pipeline WATER STEAM/HEAT Steam Generation 2010 Aspen Technology, Inc. All rights reserved 42

43 Steam Assisted Gravity Drainage (SAGD) Aspen HYSYS Model Make up Streams GAS TREATMENT Well Pad DilBit Diluent To Upgrader or Pipeline OIL TREATMENT STEAM GENERATION WATER TREATMENT 2010 Aspen Technology, Inc. All rights reserved 43

44 Steam Assisted Gravity Drainage (SAGD) DESIGN Model wellpad characteristics Model separation of water, oil, and gas phases Perform profit calculations (upgrade to SCO or sell) Consider new technology partial upgrading in-situ, combustion, VAPEX, etc. OPERATIONS Use model to make decisions in all phases of operation preheat, steam injection & oil production, and blowdown Track and report key components sulfur, etc. Determine how operating improvements Additions of diluent and/or solvents, their flow conditions, separation scheme & recovery Bitumen treatment and recovery Steam generation Water treatment (incl. softening) Increase bitumen separation/ recovery Reduce energy requirements Improve water usage 2010 Aspen Technology, Inc. All rights reserved 44

45 Agenda Heavy Oil Overview Best Practices for Modeling Heavy Oils in Aspen HYSYS Sample Applications Recommendations and Conclusions Q&A 2010 Aspen Technology, Inc. All rights reserved 45

46 Recommendations for Heavy Oils 1. For Assay data, generally suggest entering Gravity, Boiling Point Range, Watson K; For Heavy Crudes, recommend including Viscosity Bulk or Curve 2. When generating Pseudo-Components, Auto-Cut option is not the best choice for heavy oil fractionation; recommend using User Points or User Defined Ranges; generate a minimum of 4 pseudo-components per draw 3. Suggested Thermodynamic Methods are: Heavy Hydrocarbons: Light Hydrocarbons: Hydrogen Rich: Sour Water: Peng Robinson with Lee-Kesler Enthalpies Peng Robinson Peng Robinson Peng Robinson Sour 2010 Aspen Technology, Inc. All rights reserved 46

47 Recommendations for Heavy Oils 4. Verify usage of: Correlations set Extrapolation methods for property curves Fit option with light ends 5. Use Plots and Utilities to match data to model and correct for any deficiencies in data Plots: Composite, Oil Distribution Utilities: Cold Properties, BP Curves 6. Integrate lab/plant data into thermodynamic parameters 2010 Aspen Technology, Inc. All rights reserved 47

48 Recommendations for Heavy Oils 7. Aspen HYSYS can match Heavy Oils data for simulation studies as validated in three papers Hyprotech, HYSYS, and Oils Technical Audit of Heavy Oil Characterization Methods Heavy Crude Oil Handling 8. Simulation Basis Manager Chapter 4, Aspen HYSYS Oil Manager provides all the technical details and options 9. Support Knowledge Base offers many solutions on this topic Sample files Technical tips: keywords such as, viscosity, thermal conductivity, density Example file: The usage of Indexed Viscosity option in HYSYS with an example 2010 Aspen Technology, Inc. All rights reserved 48

49 Agenda Heavy Oil Overview Best Practices for Modeling Heavy Oils in Aspen HYSYS Sample Applications Recommendations and Conclusions Q&A 2010 Aspen Technology, Inc. All rights reserved 49

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57 aspenone Global Conference May 3-5, 2010 in Boston, MA 3-5 May 2010 Boston, MA, USA Westin Copley Place Focused sessions including: Aspen Process Modeling Chemicals - Aspen Plus and ACM Energy - Aspen HYSYS Family Aspen Exchanger Design & Rating (HTFS) Capital Project Engineering Aspen Economic Evaluation (Icarus) Aspen Basic Engineering (Zyqad) Batch and Pharma Process Development Format: In-depth sessions on product families, solution areas and industry verticals Panel discussions Share best practices and experiences with other users and AspenTech experts Open discussions to share new ideas and provide feedback to AspenTech Tutorials and training on latest capabilities Clear understanding of future product direction For more information: sanjeev.mullick@aspentech.com or dan.mccarthy@aspentech.com Web: Aspen Technology, Inc. All rights reserved 58

58 aspenone Global Conference May 3-5, 2010 in Boston, MA Focused sessions including: Aspen Process Modeling Chemicals - Aspen Plus and ACM Energy - Aspen HYSYS Family Aspen Exchanger Design & Rating (HTFS) Capital Project Engineering Aspen Economic Evaluation (Icarus) Aspen Basic Engineering (Zyqad) Batch and Pharma Process Development 3-5 May 2010 Boston, MA, USA Westin Copley Place More User Presentations. Format: In-depth sessions on product families, solution areas and industry verticals Track agendas are incorporating additional user presentations slots up to 100 total so attendees can see and learn how best practitioners are implementing the latest solutions. More Networking Connections... Panel discussions Share best practices and experiences with other users and AspenTech experts The 2010 program will make it easier for attendees to connect with their peers, giving more opportunities to exchange ideas that are relevant to their specific business needs. Open discussions to share new ideas and provide feedback to AspenTech More Integrated Solutions and Product Updates... Tutorials and training on latest capabilities Back by popular demand, the AspenTech Plenary Session, the Solutions Center, and dedicated product update sessions will bring more focus on integrated solutions, product news and what's ahead in product development. Clear understanding of future product direction For more information: sanjeev.mullick@aspentech.com or dan.mccarthy@aspentech.com Web: Aspen Technology, Inc. All rights reserved 59

59 Dr. Mohammad Khoshkbarchi Senior Project Manager, Process Ecology Dr. Glenn Dissinger Director, Product Management, AspenTech Sanjeev Mullick Director, Product Marketing, AspenTech Aspen Technology, Inc. All rights reserved 60