**Carbone** is an interactive fluid modelling package designed to build and tune EoS or Black Oil fluid models and perform different operations on them. Whilst the most common use case is to build a PVT model to be utilized in the KAPPA workstation or any other Black oil or compositional modeling platform, Carbone can also be used for in-depth fluid studies, including multi-sample EoS model building, wax, asphaltene and hydrates studies.

With speed and ease of use at its core, processes such as phase envelope generation, flash results and model comparison are automatically performed for any fluid and synchronized with fluid editing.

Carbone is powered by the technical kernel from IFPEN as part of our ongoing technical partnership.

Built as part of KAPPA Generation 6, Carbone has a web UI and separate back end, allowing various deployment configurations, namely stand-alone, client-server, or through the KAPPA-Automate platform as a microservice.

Carbone offers a multilingual UI, currently supporting English, French, Russian, Chinese and Spanish.

Built-in ‘standard’ (up to C_{20}) and ‘extended’ (up to C_{40}) lists are available for component selection but the user can create and save any custom scenario.

Whilst the properties of pure components are fixed, pseudo component properties (Molar Weight, Specific Gravity, and Boiling Temperature) can be overridden at load time and all other properties are recomputed automatically.

**Twu/Edmister**, **Lee-Kesler Extended**, **Riazi/Edmister** and **Pedersen** correlations are available to compute pseudo component properties.

In addition to selecting components and defining the composition and properties of a fluid in Carbone, fluids may also be initialized by importing files in Eclipse™ compositional format.

**Peng-Robinson** and **Soave-Redlich-Kwong** models are available.

An option for volume correction is also available for density correction.

Internal coherence of Acentric factor (to component boiling point) and Volume Shifts (to component surface density) maybe be forced in the model.

Users can choose to conserve mass or moles when a fluid is modified e.g. in a Regression or Characterization etc...

**Lohrenz-Bray-Clark (LBC)** and **LBC Heavy Oil** models are available for viscosity computation.

Internal coherence of Critical volumes (to **Orrick & Erbar** viscosity correlation) may be forced in the model.

To check the consistency of an EoS fluid resulting from Characterization and/or regression, multiple plots are offered:

1. Component properties (T_{c}, P_{c}, ω, Viscosity, T_{b}, V_{c}, Specific Gravity and Parachor) vs. Molecular weight

2. K_{i} vs. Pressure

3. K_{i} vs T_{bi}

Additionally, if T_{c}, P_{c} or V_{c} are not monotonic or if T_{b}’s fall outside the SCN boiling point ranges published by Katz and Firoozabadi, a warning is issued to the user.

A PT phase envelope is simulated on the fly for any fluid. Multiple phase envelopes can be compared.

Flash results, including mixture properties, oil and gas phase composition, thermodynamic, transport and thermal properties are automatically computed and output at reservoir and standard conditions. Users can also specify additional pressures and temperatures at which to compute flash results.

A detailed, multi-sample, field-wide characterization can be carried out in Carbone. The process steps include:

1. Molar Distribution Models: Choose between **Exponential** or **Gamma** distribution models and tune model parameters to match a single or multiple samples

2. Characterization Factors: Correlate molecular weight and specific gravity of one or multiple samples from a field using **Watson**, **Jacoby** or **Søreide** Characterization Factors.

3. Boiling Point Estimation: Correlate pseudo-component molecular weight and boiling points using **Twu** or **Søreide** correlation.

The tuned characterization can help QC any bad quality GC data and systematically replace bad quality GC data with reliable estimates from the model. In the absence of extended GC data, the plus fraction can also be split into heavier fractions from the characterization.

Once a characterzation is created, it can be applied to any compatible fluid, allowing users to develop field-wide EOS models.

The split process is used when the initial compositional analysis of the fluid is not sufficient to correctly simulate the laboratory experiments.The end goal is to split the plus fraction into a certain number of pseudo-components.

Carbone offers three different Split procedures:

1. Standard oil characterization to C_{80}

2. Heavy oil characterization to C_{200}

3. 'Automatic Wax': This is an automatic split scheme, used to produce a Wax fluid. All fractions with carbon number greater than N (where 6 ≤ N ≤ 16) and less than M (where 17 ≤ M ≤ 100) are split into Paraffin (P), Naphthene (N) and Aromatic (A) families. Users can specify which of the three families will form part of the solid (wax) phase.

Constrained split allows the characterization of two fluids to the same pseudo-component fractions.

Lumping is used to reduce the number of components of a given fluid. The following lumping methods are available:

1. User defined: groups of components are created by the user. Carbone computes the equivalent properties of these components and assigns them to the groups.

2. Montel Gouel: a target number of components is specified by the user. Carbone automatically groups and computes the components using the method proposed by **Montel and Gouel (1984)**.

3. SARA: This is an automatic lumping scheme, used to produce an Asphaltene fluid using **SARA** information, from the original fluid composition.

Carbone provides an automatic PNA split scheme. Each fraction with Carbon number greater than N (where 6 ≤ N ≤ 16) and less than M (where 17 ≤ M ≤ 100) is split in to the three P, N and A families. Users can specify which of the three component families will be part of the solid phase. The output of this split is a 'Wax' fluid.

Alternatively, if a fluid is already characterized into solid and non-solid forming components, the component precipitation type can be set when loading this definition.

The wax model in Carbone is derived from the one proposed by **Pedersen (1995)** and is based on the thermodynamic equilibrium between the liquid and solid (wax) phases.
The solid phase is assumed to behave ideally. All constituents of a pseudo-component do not necessarily enter into the wax phase.
The solid-liquid equilibrium ratio, K_{i}^{SL}, is zero for the non-wax-forming parts of all pseudo-components.

WAT and Wax Precipitation curves are automatically generated for any ‘Wax’ fluid.

Carbone allows input of apparent liquid viscosity (η_{apparent}) vs. shear rate data and computes fraction of crystallized wax (ɸ_{wax}) vs. shear rate using the formulation presented by **Pedersen and Rønningsen (2000)**. Plots of both η_{apparent} and ɸ_{wax} are displayed vs. shear rate.

A dedicated ‘Wax’ regression is available for ‘Wax’ fluids, allowing users to regress on Melting Point and Enthalpy of Fusion of the Wax forming components to match WAT, Wax precipitation and/or wax viscosity data.

*Note: other regression types can also be used for a Wax fluid.*

Carbone provides an automatic lumping process, which lumps any fluid into a 10-component ‘Asphaltene’ fluid, based on SARA input. The method is derived from **Scewczyk et al. (1999)**.

Following an internal study at IFPEN, the model was further tuned to speed up the Asphaltene calculation process.

Alternatively, if a fluid is already characterized into Asphaltene and non-Asphaltene fractions, component precipitation type can be set when loading this definition.

Two methods are available in Carbone:

1. De Boer's method **(De Boer et al., 1995)**

2. Colloidal Instability Index (CII) method **(Yen et al., 2001)**

3. Stankiewicz Asphaltene Stability Index (ASI) method **(Stankiewicz et al., 2002)**

The Asphaltene model in Carbone treats Asphaltene as a solubility class and models asphaltene precipitation as Liquid-Liquid demixing. All the constituents are assumed present in all phases and flocculation is considered as the appearance of a second liquid phase.

**Abdoul et al. (1991)** equation of state is used to analyze the various phases.
The entire asphaltene phase envelope for the complete PT spectrum is automatically generated.The solubility curve is also automatically generated for any ‘Asphaltene’ fluid.

A dedicated ‘Asphaltene’ regression is available for ‘Aphaltene’ fluids, allowing users to regress on Tc and Mw of the Asphaltene components to match the asphaltene onset pressure and/or precipitation data.

*Note: other regression types can also be used for an Asphaltene fluid.*

Hydrate structures of type S1 and S2 can be defined. Impact of the following additives on hydrate phase envelope can be modeled:

1. Methanol

2. Ethanol

3. MEG

Water can exist free or in a saturated state.

For a given setup and additive amount, crystallization temperature at a given pressure (and vice versa) can be calculated.

In addition, Hydrate composition and stability graph with and without the additive is also output. Different inhibitor types and concentrations can thus be studied.

The hydrate phase is modeled based on the approach proposed by van der Waals and Platteeuw (1959) and extended by Parrish and Prausnitz (1972). The fluid phase is modeled using the Cubic Plus Association (CPA) Equation of State.

The following experiments can be loaded and simulated:

1. Constant Composition Expansion (CCE)

2. Constant Volume Depletion (CVD)

3. Saturation Pressure

4. Saturation Temperature

5. Differential Liberation

6. Classical Separator

7. Swelling

Data can be easily pasted from clipboard.

In addition to fluid properties, Carbone also allows users to enter oil and/or gas compositions at each pressure step in the experiment.

These compositions may then be included in the objective function to use in regression.

The following experiments related to solid precipitation can be loaded and simulated:

1. Asphaltene Onset Pressure (AOP)

2. Asphaltene Precipitation

3. Wax Appearance Temperature (WAT)

4. Wax Precipitation

5. Wax Viscosity

Data can be easily pasted from clipboard.

The following QC methods are available for sample composition and the different lab experiments:

1. Auto-screening of sample composition for OBM contamination

2. Oil density mass balance

3. Composition forward material balance / Bashbush plot

4. Composition backward material balance

5. Z-Factor comparison with Standing & Katz chart

6. Y-Function plot for CCE, DLE and CVD experiments

7. Hoffman plot

Eight kinds of regression types are available.

1. **Classical pseudo** regresses on the following pseudo component properties: T_{c}, P_{c}, ω/T_{b}, Volume Correction/Specific gravity and K_{ij}s.

2. **Primary Variables** on pseudo component Tb and Specific Gravity, with automatic recomputation of all derived properties,

3. **EoS parameters** on Ωa and Ωb parameters,

4. **Viscosity Model** on Critical Volumes and Modified LBC parameters,

5. **Automatic Heavy**, on the boiling point of the heaviest fraction to match on the liquid density at standard conditions,

6. **Mw+**, on molecular weight of the plus fraction to match saturation pressure,

7. **Asphaltene**, on Tc and Molecular weight of Asphlatene fractions,

8. **Wax**, on Melting Point and Enthalpy of Fusion of Wax fractions.

Two solvers are available for regression: KAPPA and Hubopt.

Regression variables may be independently varied or constrained using a constant or ramped multiplier.

Multi-fluid regression is offered, where a given regression can use data from multiple lab reports and compositions from multiple fluids to arrive at a common EoS model.

If fluid compositions have been loaded for different pressure steps in lab experiments, they can be included in the objective function for regression

Fluids properties can be defined using a broad range of Black Oil correlations (see Technical References). These correlations can also be tuned to user data.

Alternatively, properties may be defined from user tables.

A Black Oil fluid may also be initialized from either KAPPA or Eclipse™ BO files.

The following Black Oil fluid types can be created:

1. Dry Gas (Hydrocarbon, Pure N_{2} or Pure CO_{2})

2. Wet Gas

3. Condensate

4. Dead Oil

5. Saturated Oil

6. Volatile Oil

Water can be included with any of the fluid type.

Flash results, including mixture properties, oil and gas phase thermodynamic and transport properties are automatically computed and output at reservoir conditions. Users can also specify additional pressures and temperatures at which to compute flash results.

A P-x phase envelope is simulated on the fly for Modified Black Oil formulation (Condensate and Volatile Oil Fluid Types).

Multiple phase envelopes can be compared.

Carbone offers the following compositional formats to export fluid PVT:

1. XML compositional (for KAPPA applications)

2. Eclipse™ compositional

3. PROSPER™ compositional

4. CMG compositional (GEM™)

5. OLGA: EoS CTM, EoS TAB and Wax Table

Black oil tables can be generated for a compositional fluid and exported in one of the following formats:

1. KAPPA BO

2. Eclipse™ BO

3. CMG BO (IMEX™)

Reservoir depletion processes can be modeled using **CCE**, **CVD** or **DLE**. Surface separator train can be defined for the export.

Properties for black oil fluids may be exported in tabular format.

Additionally, an XML output of the black oil fluid setup can be created for easy transfer to other KAPPA modules.

For samples which may have been contaminated by Oil Based Mud (OBM), two methods are available to ‘clean’ the sample composition:

1. Skimming: Assumes an exponential molar distribution model for the uncontaminated fluid; used when the mud composition and contamination are not known.

2. Subtraction: used when the mud composition and contamination are known.

An automatic screening is performed on the sample composition to check for possible contamination. If suspected, a warning is issued to the user:

A separation process is a PT flash at a given pressure and temperature. The inputs to this flash are the feed composition, pressure and temperature.

The output of a separation process is two fluids: separation gas and separation oil. Multiple separators can be connected to either stream to design a separator train.

The mixer option allows the user to mix two different fluids.

The second fluid may be one of the existing fluids in the document or a single fluid component.

There are different mixing criteria available: ‘Target GOR’, ‘Molar fraction of the secondary fluid’, ‘Volume fraction of secondary fluid’ and ‘Miscibility pressure’.

In the absence of direct stock-tank measurements, the shrinkage option can be used to reliably convert oil rates, measured at test/line conditions to standard conditions.

There are two main inputs to these calculations:

1. Device information: Pressure, Temperature and measured Oil and Gas rates

2. Separator information: Pressure and Temperature of different separator stages in the production/processing facility

The results of these calculations are:

1. Well stream composition, honoring device production ratios

2. Fluid composition at each separation stage

3. Oil and gas rates and properties at each separation stage

4. Shrinkage value

An optimization option allows separator pressure and temperature optimization to minimize shrinkage over a given number of separtor steps.

The compositional gradient process calculates the variations in composition and properties of a reservoir fluid as a function of reservoir depth.

For any depth, compositions can be output as a new ‘Fluid’ on which any process may be applied.