CCQTA Bitumen Dewatering and Volumetric correction...• This method is best described in “ASTM...

CCQTA BITUMEN DEWATERING AND

VOLUMETRIC CORRECTION

This project was created to set guidelines for the best practices when preparing bitumen samples for analytical work, as well as assess the

applicability of API 12.3 “Calculation of Volumetric Shrinkage Resulting from Blending Light Hydrocarbons and Crude Oil” to blends of bitumen and

practical diluents.

April 15, 2016

Participants Project Manager Alberta Energy Bill Lywood Alberta Innovates – Technology Futures Crude Quality Inc. Cenovus [email protected] ConocoPhillips Author Husky Sam Lywood Maxxam Crude Quality Inc. Suncor [email protected]

April 15, 2016 Table of Contents

Executive Summary ................................................................................................................................... 3

Original Scope ....................................................................................................................................... 3

Expanded Scope .................................................................................................................................... 3

Sample Preparation .................................................................................................................................. 4

Sample Description and Properties .......................................................................................................... 7

Blending Procedure ................................................................................................................................... 7

API 12.3 Volumetric Shrinkage Resulting from Blending Light Hydrocarbons with Crude Oils ................ 8

API 12.3 Overview ................................................................................................................................. 8

API 12.3 Limits ....................................................................................................................................... 9

Blend Study Results ............................................................................................................................... 9

Correction Factor for API 12.3 When Blending Native Bitumen with Diluent .................................... 14

Error Summary .................................................................................................................................... 16

Limitations........................................................................................................................................... 17

Conclusions and Recommendations ....................................................................................................... 18

Bitumen Dewatering ........................................................................................................................... 18

Volumetric Correction ......................................................................................................................... 18

Appendix A: Laboratory Operating Procedures ...................................................................................... 19

List of Tables Table 1: Bitumen Properties ......................................................................................................................... 7 Table 2: Diluent Properties ........................................................................................................................... 7 Table 3: Error on Volumetric Shrinkage Calculations by Bitumen .............................................................. 17 Table 4: Error on Volumetric Shrinkage Calculations by Diluent ................................................................ 17

List of Figures Figure 1: Sample Preparation Flowchart ...................................................................................................... 6 Figure 2: 975 Ideal Blend Performance......................................................................................................... 9 Figure 3: 1000 Ideal Blend Performance..................................................................................................... 10 Figure 4: 1010 Ideal Blend Performance..................................................................................................... 10 Figure 5: 1020 Ideal Blend Performance..................................................................................................... 11 Figure 6: 975 API 12.3 Performance ........................................................................................................... 12 Figure 7: 1000 API 12.3 Performance ......................................................................................................... 12

Bitumen Dewatering and Volumetric correction Page 1 of 20

April 15, 2016 Figure 8: 1010 API 12.3 Performance ......................................................................................................... 13 Figure 9: 1020 API 12.3 Performance ......................................................................................................... 13 Figure 10: 975 API 12.3 with Correction Performance ............................................................................... 14 Figure 11: 1000 API 12.3 with Correction Performance ............................................................................. 15 Figure 12: 1010 API 12.3 with Correction Performance ............................................................................. 15 Figure 13: API 12.3 with Correction Performance ...................................................................................... 16


April 15, 2016 Executive Summary Alberta bitumen is extracted from the ground in numerous ways and from greatly varying formations. This results in a slurry of water, sand, and oil with the possibility of a tight emulsion. Analysis of bitumen requires the removal of water and sediment while impacting the bitumen as little as possible. This is an imperfect process and the best that can be offered is a recommended best practice for cleaning Alberta bitumen. Different preparation techniques can result in slightly different clean bitumen. A recommended best practices method ensures that a similar preparation method is used between samples and allows for the best comparison.

Transportation of crude oil is essential in the petroleum industry and blends of crude oil are often created to meet specifications and efficiently move oil. This is particularly true in Western Canada, as vast reserves of heavy viscous crudes need to be shipped. Based on their intrinsic properties, conventional heavy and oil sands derived crudes need to be blended with diluent to reduce their high viscosities. Blends of bitumen and diluent, known as dilbit, are commonly created as a medium in which these heavy high viscosity crudes can be shipped efficiently. When blending any two or more crudes of varying composition, there is a deviation from ideal behavior which, in the petroleum industry, usually results in loss of volume. In short, when one mixes one volume of bitumen with one volume of diluent the result is less than two volumes of dilbit. This phenomenon is known as volumetric shrinkage. As delivery measurements are recorded by volume at both the input and output locations, it is essential to have a model for predicting shrinkage as accurately as possible. This allows suppliers and shippers to differentiate between volume lost due to shrinkage and volume lost through the system. An accurate estimation of shrinkage would also impact the predictability of blending operations.

Original Scope When this project was initially proposed to the CCQTA, focus was primarily meant to cover dewatering and shrinkage. It was realized fairly early on in the project that Alberta Energy would be doing extensive work involving various techniques to bitumen extraction for their Bitumen Assay Program. Coordination between the two projects would result in one document of recommendations for public release. Shrinkage would be evaluated on Alberta bitumens through a traditional blend study and the results would be compared with previously established models. These results would lead to either the modification of an established model to include heavy Alberta hydrocarbons or creation of a new model.

Expanded Scope During meetings involving the project participants, it was decided to expand the scope of this project to include blended viscosity modelling. Having such a large group of carefully prepared and blended samples provided an excellent opportunity to evaluate viscosity for all of these mixtures. Requiring three or four measurements at various temperatures, analytical work related to viscosity measurement became a significant portion of the project. The viscosity related data have been separated into a standalone project and are not part of this report.


April 15, 2016 Sample Preparation As part of the Bitumen Assay Project, Crude Quality Inc. proposed a starting point for discussions, and participated in a cooperative evolution of a standardized extraction method for native bitumen. The developed process is applicable to all bitumen samples, regardless of their native nature or production technique. The process yields bitumen that has been isolated from production fluids to the degree where reliable assay distillations are achievable on a consistent and repeatable basis.

The challenges in sample collection and preparation are to collect the samples in a manner to retain lighter components (Dean-Stark Distillations prove inadequate for this reason) and to subsequently isolate the bitumen from the water and solids (the laboratory’s initial objectives were 0.5 vol%, as per industry standard pipeline specifications). Collecting bitumen samples prior to diluent addition, however, means that sediment and water would be included in high concentrations in the samples. Finding an effective way to remove these contaminants without affecting the bitumen was critical to this project.

The steps outlined below for the recommended method have been designed to meet these challenges:

1. Using thermal methods to break emulsions present in the produced fluids

2. Distilling water from the native bitumen while simultaneously isolating and retaining lighter components (“lighter” components in bitumen are C8’s x C12’s)

• Water removal by distillation can be conducted through a variety of methods, including but not limited to, rotary evaporation with or without vacuum and ASTM D5236 vacuum distillation.

• Condensed vapours may be recovered using standard cooling coils circulating chilled glycol and dry ice traps.

• Observations in the Bitumen Assay Program indicate that the vacuum rotary evaporation method employed was consistently capable of producing native bitumen with water concentrations below the 5000 mg/kg level. There may be limited need to distill the sample beyond this point, however laboratories can be anticipated to reduce bound water concentrations to values less than 5000 mg/kg on a regular and routine basis simply to make sure that they have achieved that upper limit.

• Phase separation can then be conducted on the overheads to isolate the hydrocarbon light ends from distilled water using a separatory funnel, and the former will be recombined with the clean bitumen in the final step

3. Modifying the bitumen density with toluene (Cold Extraction)

• Reducing the native bitumen density and viscosity with toluene vastly improves the subsequent bitumen extraction processes and the capability to keep the native bitumen “whole”. Since the toluene is added quantitatively, it can be removed and accounted for


April 15, 2016 quantitatively. The “tol-bit” blend density target of 960 kg/m3 is not cast in stone, and minor deviations from this target should be considered acceptable. The “tol-bit” target density is meant to balance toluene consumption and subsequent extraction efficiencies.

• In the process of the investigation, it was repeatedly demonstrated that the use of toluene does not alter the chemical properties or constituents of the native bitumen and that its impact on the physical properties (density, viscosity) can be corrected for the measurable residual in the “clean” bitumen.

4. Using centrifuge methods to separate the solids from the density modified bitumen

• This method is best described in “ASTM D4007 - 11 Standard Test Method for Water and Sediment in Crude Oil by the Centrifuge Method”. The centrifuge does not physically alter the bitumen, does not require solvent addition and can provide for thermal control.

• Experience indicated that solids and sediment concentrations can be reduced to less than 500 mg/kg using the centrifuge technique(s), thereby minimizing the influence of solids concentration and density variations on the final native bitumen density calculations.

• As a target based on the review of sediment density impacts and the composition of typical sediments, it is recommended that 1000 mg/kg sediment by ASTM D4807 be the upper limit in the centrifuged “tol-bit” blend. It was observed, and it is anticipated, that sediment concentrations of less than one-half this upper limit are consistently achievable using equipment, personnel and processes employed at all hydrocarbon laboratories in the industry.

5. Rotary evaporation to remove toluene

6. Recombination and reconstitution of hydrocarbon components.

• The weights for all components are compiled to a data management spreadsheet and a ratio of light ends to bitumen is calculated. Light ends and clean bitumen are recombined according to this calculated ratio. Note that the weight of clean bitumen before solids removal is used to calculate the ratio while recombination occurs after solids removal. The weight of solids removed compared to the mass of clean bitumen is considered insignificant.

Below is a detailed diagram of the recommended extraction process.


April 15, 2016

COMBINE**

COLD EXTRACTION

CENTRIFUGE

Distillation / Rotovap*

BITUMEN /

EMULSION

WATER and LIGHT

ENDSBITUMEN

WATER LIGHT ENDS

Phases separation

Sediment Content <0.5

mass%

SOLIDS FREE

BITUMEN

BITUMEN WITH

SOLIDS

YES

CLEAN BITUMEN ready for

BAP

NO

TOLUENE

Add enough For density<960 kg/m3

BITUMEN WITH

TOLUENE

SOLIDS

ROTOVAPTOLUENE

* Oil-in-water and water-in-oil emulsions are processed separately

in order to minimize the effect of bitumen thermal treatment

** Blending ratios are corrected for bitumen losses

Figure 1: Sample Preparation Flowchart

The mass balance procedure for the process flowchart above, as provided by the laboratory, can be found in Appendix A


April 15, 2016 Sample Description and Properties Bitumen samples were obtained from the Alberta Energy Bitumen Assay Program. Retains that were set to be discarded were instead used for this project. The bitumen samples were not required to be representative of any specific production, so minor changes to composition during storage are inconsequential. Samples were chosen in an effort to cover variability seen from typical Alberta bitumens. Density, production type, producing formation, and region were all considered when selecting samples. A summary of bitumen properties can be seen in the table below:

Name Density (kg/m3)

Viscosity (cSt)

Sediment Water

15°C 70°C 80°C 90°C (ppmw) (ppmw) 975 Bitumen 973.2 124.4 76.8 49.85 5746 2876 1000 Bitumen 999.5 302.0 178.8 112.7 2612 5910 1010 Bitumen 1004.9 1340 710.5 399.4 4887 463 1020 Bitumen 1019.8 3124 1521 791.2 232 1190 Table 1: Bitumen Properties

Due to wide variability and often unpredictability of diluent quality in Alberta, four lab manufactured diluents were created to cover the spread of common diluents. Interest in a much lighter diluent was expressed later into the project and a fifth was added to the blend study as received. In addition to traditional C5+ condensates, a sweet synthetic diluent was manufactured from a mixture of readily available synthetics. A summary of diluent properties can be seen in the following table:

Name Density (kg/m3)

Viscosity (cSt)

15°C 0°C 5°C 10°C 20°C Diluent A 741.0 1.251 1.185 1.111 - Diluent B 724.3 0.9860 0.9353 0.8865 - Diluent C 707.7 0.8449 0.7898 0.7500 - Diluent D 690.3 0.6834 0.6527 0.6214 - Super Light 663.0 0.5130 0.4924 0.4727 - Sweet Synthetic 863.3 12.01 - 8.329 5.966

Table 2: Diluent Properties

Blending Procedure Rough drafts of the blending procedure were circulated to participating members prior to the start of any bench work. Consensus was agreed that the procedure, provided by the lab, followed best practices for maintaining sample integrity throughout the entire process.


April 15, 2016 API 12.3 Volumetric Shrinkage Resulting from Blending Light Hydrocarbons with Crude Oils

API 12.3 Overview In 1962 the American Petroleum Institute (API) created API 2509C1 to perform shrinkage calculations. As this method was created based on empirical analysis, it was intended to be valid for a range of crude oil densities and light component concentrations. In the 1980’s as the frequency of crude blending increased, industry demanded a correlation with greater accuracy. Data sets from multiple contributors were combined to determine a new correlation covering a wider range of densities and light component concentrations from 0% to 100%. The formula used for API 2509C was also adjusted to permit calculations at 0% and 100% concentration of the lower density constituent. This led to the publication of API 12.32 in 1996, a revised formula for calculating volumetric shrinkage. Like API 2509C, API 12.3 was based off empirical results and thus was limited to a specific range of densities. However API 12.3 did offer an improvement on 2509C. By restricting data to 15°C (60°F) and between 100 kPa (15 psia) and 700 kPa (115 psia), API 12.3 reduced error caused by variations in temperature and pressure. Data for API 12.3 was collected from previous work on shrinkage by Childress3, Scott4, and Schuchardt5. A summary of this data can be found in Tables B-1, B-2, and B-36 respectively in the API 12.3 documentation. It should be noted that although the upper range listed is 979 kg/m3, there are only 18 data points above 936 kg/m3.

API 12.3 is represented by the following formulae:

Imperial: 𝑆 = 4.86 ∗ 10−8𝐶 (100 − 𝐶)0.819𝐺2.28

Metric:

𝑆 = 2.69 ∗ 104𝐶(100− 𝐶)0.819 �1𝑑𝐿

−1𝑑𝐻

�2.28

Where: S = Volumetric Shrinkage, as percent of total mixture ideal volume C = Concentration, as liquid volume percent of lighter component G = Gravity Difference, in degrees API dH = Density of Heavy Component, in kg/m3

1 Volumetric Shrinkage resulting from blending volatile hydrocarbons with crude oils, American Petroleum Institute (API) Bulletin 2509C. 2 API Manual of Petroleum Measurements Standards, Chapter 12 Calculation of Petroleum Quantities, July 1996 3 H.M. Childress. “Volumetric Shrinkage Occurring in Blending Indirect Products Such as Butane, Natural Gasoline, and Produced Distillates with Crude,” Project No. 1237, Exxon Research and Engineering Company, May 1955 4 P.R. Scott. “Volumetric Shrinkage of Crude-Volatile Blends,” Technical Report No. 3-61, Shell Pipeline Corporation, Houston, Texas, January 1962. 5 K. Schuchardt. “Volumetric Shrinkage Resulting from Blending Crude Oils,” DGMK-Project 405, July 1991 6 API Manual of Petroleum Measurements Standards, Chapter 12 Calculation of Petroleum Quantities, July 1996 pp. 87-89


April 15, 2016 dL = Density of Light Component, in kg/m3

API 12.3 Limits Light component density within 581 – 889 kg/m3 Heavy component density within 644 – 979 kg/m3 Temperatures near 15°C or 60°F

Blend Study Results Blends of heavy Alberta bitumen and diluent conformed to past observations made with more traditional blends of crude oils. Greater separation in density between the 2 mixing components led to greater amounts of volumetric shrinkage.

Reliable density measurements were difficult to obtain, possibly due to incomplete homogeneity or interference from solids and water that cannot be completely extracted from the bitumen samples. Considerable effort was required from the lab to get the best possible results. Density measurements were reviewed to make sure linear correlations were observed. If a particular measurement was considered an outlier, a new blend was made from scratch.

The following performance charts show the effects of shrinkage compared to ideal mixing behaviour on a per bitumen basis. Deviation of the raw data from the unit slope is indicating the degree of shrinkage.

Figure 2: 975 Ideal Blend Performance

R² = 0.9998

R² = 0.9998

R² = 0.9998

R² = 0.9999

R² = 0.9999

R² = 0.9998

870

880

890

900

910

920

930

940

950

960

870 880 890 900 910 920 930 940 950 960

Idea

l Ble

nd D

ensi

ty

Measured Density

975 Bitumen

Diluent A Diluent B Diluent C Diluent D

Super Light Sweet Synthetic unit slope


April 15, 2016



R² = 0.9999

R² = 0.9997

R² = 0.9997

R² = 0.9998

R² = 0.9996

R² = 0.999

890

900

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920

930

940

950

960

970

980

890 900 910 920 930 940 950 960 970 980

Idea

l Ble

nd D

ensi

ty

Measured Density

1000 Bitumen



R² = 0.9985

R² = 0.9997

R² = 0.9998

R² = 0.9998

R² = 0.9993

R² = 0.9998

890

900

910

920

930

940

950

960

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980

990

890 900 910 920 930 940 950 960 970 980 990

Idea

l Ble

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ensi

ty

Measured Density

1010 Bitumen




April 15, 2016


If we apply API 12.3 correction to the raw data, all results line up parallel with the unit slope. However there is a slight bias that causes API 12.3 to under predict density in virtually all cases. The following performance charts summarize this effect. Visually, the bias is represented by all data points lying just below the unit slope line.

R² = 0.9999

R² = 0.9999

R² = 0.9993

R² = 0.9999

R² = 0.9999

R² = 0.9999

900

910

920

930

940

950

960

970

980

990

1000

900 910 920 930 940 950 960 970 980 990 1000

Idea

l Ble

nd D

ensi

ty

Measured Density

1020 Bitumen

Diluent A Diluent B Diluent C Diluent DSuper Light Sweet Synthetic unit slope


April 15, 2016

Figure 6: 975 API 12.3 Performance


880

890

900

910

920

930

940

950

960

880 890 900 910 920 930 940 950 960

API 1

2.3

Calc

ulat

ed D

ensi

ty

Measured Density

975 Bitumen



900

910

920

930

940

950

960

970

980

900 910 920 930 940 950 960 970 980

API 1

2.3

Calc

ulat

ed D

ensi

ty

Measured Density

1000 Bitumen




April 15, 2016



900

910

920

930

940

950

960

970

980

990

900 910 920 930 940 950 960 970 980 990

API 1

2.3

Calc

ulat

ed D

ensi

ty

Measured Density

1010 Bitumen



910

920

930

940

950

960

970

980

990

1000

910 920 930 940 950 960 970 980 990 1000

API 1

2.3

Calc

ulat

ed D

ensi

ty

Measured Density

1020 Bitumen




April 15, 2016 Correction Factor for API 12.3 When Blending Native Bitumen with Diluent In order to create a correction factor for API 12.3, measured shrinkage was compared with calculated shrinkage by simply taking the residual squared. Then by minimizing the sum of residuals squared by changing the coefficient of the API 12.3 formula, a correction factor was determined. Using the data from this blend study, results with the least error were obtained by using the following:

Imperial:

𝑆𝐴𝐵 𝐵𝑖𝑡𝑢𝑚𝑒𝑛 = 𝟓.𝟕𝟑 ∗ 𝟏𝟎−𝟖𝐶 (100 − 𝐶)0.819𝐺2.28

Metric:

𝑆𝐴𝐵 𝐵𝑖𝑡𝑢𝑚𝑒𝑛 = 𝟑.𝟏𝟕 ∗ 𝟏𝟎𝟒𝐶(100 − 𝐶)0.819 �1𝑑𝐿

−1𝑑𝐻

�2.28

Or by using the correction factor:

𝑆𝐴𝐵 𝐵𝑖𝑡𝑢𝑚𝑒𝑛 = 1.179 ∗ 𝑆𝐴𝑃𝐼 12.3

A simple correction factor for Alberta Bitumen is suitable due to the consistent but slight bias observed in API 12.3. Any further alterations to the formula presented in API 12.3 or the creation of a new formula was deemed unnecessarily complicated with limited benefit. Performance charts are included below:

Figure 10: 975 API 12.3 with Correction Performance

880

890

900

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960

880 890 900 910 920 930 940 950 960

Calc

ulat

ed D

ensi

ty A

PI 1

2.3

with

Cor

rect

ion

Foac

tor

Measured Density

975 Bitumen




April 15, 2016



900

910

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930

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900 910 920 930 940 950 960 970 980

Calc

ulat

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PI 1

2.3

with

Cor

rect

ion

Foac

tor

Measured Density

1000 Bitumen



900

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900 910 920 930 940 950 960 970 980 990

Calc

ulat

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PI 1

2.3

with

Cor

rect

ion

Foac

tor

Measured Density

1010 Bitumen




April 15, 2016

Figure 13: API 12.3 with Correction Performance

Error Summary The following error formulae7 were used to quantify error on the volumetric shrinkage data:

Average Absolute Error = ∑ ��𝑆𝐶−𝑆𝐸�𝑖

𝑁�𝑁

𝑖=1

Average Bias Error = ∑�𝑆𝐶−𝑆𝐸�𝑖

𝑁𝑁𝑖=1

Root Mean Square Error = �∑ [𝑆𝐶−𝑆𝐸]𝑖2

𝑁𝑁𝑖=1

Where:

SE = experimental volumetric shrinkage, as a percent of total volume SC = calculated volumetric shrinkage, as a percent of total volume N = number of data points

The following table summarizes the error observed using the traditional API 12.3 calculation and with the proposed correction factor for Alberta bitumen. In all cases, the prediction using a correction factor produced error smaller than calculations using the tradition API 12.3 formula.

7 API Manual of Petroleum Measurements Standards, Chapter 12 Calculation of Petroleum Quantities, July 1996 pp. 84

910

920

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940

950

960

970

980

990

1000

910 920 930 940 950 960 970 980 990 1000

Calc

ulat

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ensi

ty A

PI 1

2.3

with

Cor

rect

ion

Foac

tor

Measured Density

1020 Bitumen




April 15, 2016 Group Name

Average Absolute Error API 12.3

Average Absolute Error Corrected API 12.3

RMSE API 12.3

RMSE Corrected API 12.3

Bias Error API 12.3

Bias Error Corrected API 12.3

975 Bitumen 0.060 0.039 0.071 0.047 0.060 0.008

1000 Bitumen 0.113 0.075 0.126 0.092 0.112 0.051

1010 Bitumen 0.079 0.040 0.093 0.054 0.079 0.016

1020 Bitumen 0.072 0.040 0.079 0.046 0.072 0.004

Table 3: Error on Volumetric Shrinkage Calculations by Bitumen

Group Name

Average Absolute Error API 12.3

Average Absolute Error Corrected API 12.3

RMSE API 12.3

RMSE Corrected API 12.3

Bias Error API 12.3

Bias Error Corrected API 12.3

Diluent A 0.083 0.053 0.104 0.074 0.083 0.037

Diluent B 0.082 0.042 0.097 0.062 0.082 0.027

Diluent C 0.069 0.045 0.084 0.055 0.069 0.002

Diluent D 0.101 0.036 0.106 0.044 0.101 0.020

Super Light 0.081 0.055 0.094 0.068 0.079 -0.029

Sweet Synthetic 0.071 0.059 0.078 0.068 0.071 0.059

Table 4: Error on Volumetric Shrinkage Calculations by Diluent

Limitations API 12.3 and the correction factor established here were obtained purely using empirical data. A best fit was calculated by minimizing the error between measured and calculated values. Because of this, API 12.3 and this correction factor should only be used with representative data. For the creation of this correction factor, effort was made to cover as wide a range as possible while being applicable to typical bitumen production and blending. Conventional bitumen and condensate were chosen for this study, as opposed to more niche products such as cracked feedstocks or manufactured diluents. For the most accurate volumetric shrinkage results it is recommended that a unique blend study be performed using actual components.


April 15, 2016 Conclusions and Recommendations

Bitumen Dewatering Extraction of low water and solids containing bitumen from produced fluids can be consistently accomplished using the prescribed methodology. Bitumen prepared by this technique results in the cleanest, least impact from preparation, and highly comparable samples. It is recommended that this methodology be released to the public domain with website access and peer communication.

Volumetric Correction Empirical modelling indicates that applying a simple arithmetic correction factor to the existing API 12.3 formula provides better accuracy and precision for calculating blend volume using mixtures of typical Alberta bitumen and diluent. It is recommended that these findings be made available to the public domain with website access and peer communication. It is also recommended that these findings be forwarded to the American Petroleum Institute for further consideration.


April 15, 2016 Appendix A: Laboratory Operating Procedures


April 15, 2016


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