Heavy Oil Simulation

© 2010 Aspen Technology, Inc. All rights reserved© 2010 Aspen Technology, Inc. All rights reserved

Engineering Excellence Webinar Series

26 January 2010

Modeling Heavy Oils in Aspen HYSYS

© 2010 Aspen Technology, Inc. All rights reserved | 2

Modeling Heavy Oils in Aspen HYSYS

• Dr. Mohammad Khoshkbarchi

− Senior Project Manager, Process Ecology

− Email: [email protected]

• Sanjeev Mullick

− Director, Product Marketing, AspenTech

− Email: [email protected]

• http://support.aspentech.com

mailto:[email protected]


http://support.aspentech.com/


Agenda

Heavy Oil Overview

Best Practices for Modeling Heavy Oils in Aspen HYSYS

Sample Applications

Recommendations and Conclusions

Q&A


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


Comparative Oil Properties

Conventional Crude <~ 30,000 cSt

Conventional Heavy 30,000 – 40,000 cSt

Thermal Heavy 200,000 – 250,000 cSt

Diluent 0.5 – 11.0 cSt

Oil Viscosity:

Oil API:

Conventional Crude > 25 °API

Conventional Heavy 25 – 18 °API

Extra Heavy (Thermal) 20 – 12 °API

Tar Sand 12 – 7 °API


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


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 5000-10,000 cP, and higher (up to 100,000 cP)

2. Venezuela

– Mainly heavy oil

– Viscosity within a range of 1000-5000 cP


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


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


Agenda

Heavy Oil Overview


Sample Applications


Q&A


Oil Properties Build PFDAssay Setup

Best Practices Workflow

Enter Assay

lab data

Check

Correlation set

Enter User

Cutpoint

ranges

Verify/alter

Extrapolation

& Conversion

Methods

Blend Assay &

Cut into Hypos

Compare

Property Plots

Install Oil

Blend Oil &

Water streams

Alter emulsion

viscosity, if

necessary

Incorporate

entrainment

Use Utilities to

check products


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


• Alternative Methods:

− ASTM D86 (atmospheric batch distillation)

− ASTM D1160 (vacuum batch distillation)

− ASTM D2887 (chromatography)

• Usually unsuitable for heavy crudes

True Boiling Point Curve

0

200

400

600

800

1000

1200

0 20 40 60 80 100

Volume % Distilled

Bo

lin

ing

Po

int

(C)

IBP

FBP

IBPi FBPi

True Boiling Point (TBP)


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


• Heavy oil TBP has much fewer experimental points

• No FBP or close point to it

Conventional Oil TBP

-100

0

100

200

300

400

500

600

700

800

0 20 40 60 80 100

Volume % Distilled

Bo

lin

ing

Po

int

(C)

Heavy Oil TBP

0

200

400

600

800

1000

1200

0 20 40 60 80 100

Volume % Distilled

Bo

lin

ing

Po

int

(C)



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


Best PracticesSpecify Properties for Heavy Oils

• Bulk property options include:

– Molecular Weight > 16

– Mass Density = 250 ~ 2000 kg/m3 Required

– Watson K Factor = 8 ~ 15 Recommended

– Bulk Viscosity, @ 100°F and @210°F Required

• Add other property curves

– Molecular Weight curve

– Density curve Recommended

– Viscosity curve (two curves) Recommended


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


Best PracticesCreating Hypotheticals for Heavy Oils

• When generating pseudocomponents for heavy oil fractionation, recommend using User Points or User Defined Ranges

• How many?

– Minimum of 4 pseudo-components 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‖?


• 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

True Boiling Point Curve

0

200

400

600

800

1000

1200

0 20 40 60 80 100

Volume % DistilledB

olin

ing

Po

int

(C)

• Solution:

− Use a guide point such as FBP or IBP

− Use other distribution



Best Practices Predict Heavy Oil Fractions

• Use the Distribution Plot to help predict crude products

– Enter custom cutsto 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‖?


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!


Best PracticesStream 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


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

Aspen HYSYS Can Accurately Predict Important Heavy Crude Properties


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


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 canresult 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.


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.


Curve Fitting Options

– Curve Includes L.E.

– Bulk Value

– Bulk Value Incl. L.E.

– Head %

– Head Adjust Weight

– Main %

– Main Adjust Weight

– Tail Adjust Weight

• For each input curve, can specify:


Curve Fitting OptionsExample 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)


Curve Fitting Options Example


Curve Fitting OptionsExample 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 re-adjust the curve to the overall crude

• Solution: Choose to fit with or without light ends, asappropriate:

– 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


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.


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


Heavy Crude Viscosity Trends

Full Crude Viscosity vs. Temperature

0

20000

40000

60000

80000

100000

120000

0 50 100 150

Temperature (C)

Vis

co

sit

y (

cS

t)

Cut Viscosity vs. Final Boiling Point

0

50000000

100000000

150000000

200000000

250000000

0 200 400 600 800 1000 1200

FBP (C)

Vis

co

sit

y (

cS

t)• Use two points from full crude viscosity curve.

• High FBP viscosities are usually a result of extrapolation using a log(log) approach.


Viscosity CurvesExample 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 extra-polation 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


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


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


Example: Improving Thermal Conductivity

Alter coefficients

Regress data


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


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


Agenda

Heavy Oil Overview


Sample Applications


Q&A


Well Pad Emulsion

DILUENT/SYNTHETIC CRUDE

STEAM/HEAT

To Upgrader or Pipeline

Gas-Oil-Water

Separation

[DILBIT/

SYNBIT]

OIL

GAS

Gas Treating

RECOVERED DILUENT/SCO

SOUR GASES

SWEET GASES

Steam Assisted Gravity Drainage (SAGD)

Steam Generation

WATER


STEAM GENERATION

GAS TREATMENT

Well Pad

Diluent

OIL TREATMENT

To Upgrader

or Pipeline

DilBit

Make up Streams

WATER TREATMENT


Aspen HYSYS Model


OPERATIONSDESIGN

• 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

• 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.


– 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


Agenda

Heavy Oil Overview


Sample Applications


Q&A


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: Peng Robinson with Lee-Kesler Enthalpies

Light Hydrocarbons: Peng Robinson

Hydrogen Rich: Peng Robinson

Sour Water: Peng Robinson Sour



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



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


Agenda

Heavy Oil Overview


Sample Applications


Q&A


50

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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

3-5 May 2010 Boston, MA, USA

Westin Copley Place

For more information:

Email: [email protected] or [email protected]: http://www.aspentech.com/aspenoneglobalconference


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Dr. Mohammad KhoshkbarchiSenior Project Manager, Process EcologyEmail: [email protected]

Dr. Glenn DissingerDirector, Product Management, AspenTechEmail: [email protected]

Sanjeev MullickDirector, Product Marketing, AspenTechEmail: [email protected]




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Heavy Oil Simulation

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