Defining the PVT Defining the Reservoir Fluid Oil: this option uses oil as the primary fluid in the reservoir, any gas cap properties will be treated as dry gas

Gas (Dry and wet): wet gas is handled under the assumption that all liquids condensation occurs at the separator. The liquid is put back into the gas as an equivalent gas quantity. The pressure drop is therefore calculated on the basis of a single phase gas, unless water is present

Retrograde Condensate: this model takes into account liquid dropout in the reservoir at different pressures and temperatures

General: this allows a tank to be treated as an oil leg with a gas cap containing a condensate rather than dry gas. In other words a tank can be treated as an oil tank with an initial condensate gas cap or as a condensate tank with an initial oil leg. The first step in entering the PVT data in the fluid properties dialogue box

Enter the following:

Formation GOR: is the GOR at bubble point and should not include free gas production

Oil gravity

Gas gravity

Water salinity

Mole percentage H2S

Mole percentage CO2

Mole percentage N2

Appropriate separator: single or two stage

Select the correlation to apply

Uncheck the “use tables” box if the PVT tables have been entered and you dont want to use them instead of the correlation

Uncheck the “use matching” box if the correlation have been matched and you want to use the original unmatched correlation

Check the “Controlled Miscibility” box and enter the gas remixing percentage if you want to control how free gas redissolves into the oil if the pressure of the fluid increases Correlation Where only basic PVT data is available, the program uses traditional black oil correlations, such as Glaso, Beal, and Petrosky etc. Open the PVT dialog box, and enter the following data:

Formation GOR

Oil gravity

Gas Gravity

Water Salinity

Mole percentage H2S

Mole percentage CO2

Mole percentage N2

Then choose the correlation you want MBAL to use to calculate the rest of the data

Click “Done” Matching Where both basic fluid data and some PVT laboratory measurements are available, MBAL modifies the black oil correlation to best-fit the measured data using a non-linear regression technique. This facility can be accessed by clicking the “Match” command in the fluid properties dialogue box.

Up to 50 PVT tables can be entered which are sorted by temperature

The data can be entered manually or imported from an excel sheet Once the data is entered, click on “match” and after the matching box appears click on “calc” to start the calculation.

To view the match coefficients and fluid properties click on “match param” box, if the data obtained after matching is good for you then click on “done” “done” till you reach the fluid properties dialogue box and then check the “use Matching” box, if not then uncheck it. Tables Is when detailed PVT laboratory data is available. MBAL will use the data in the PVT tables in all further calculations only if the “use tables” box is ticket. Up to 50 PVT tables can be entered and each table may use a different temperature, if the program requires data that is not entered in the tables it will calculate it using the selected correlations.

To access the PVT tables click on the “Table” icon, and enter the data either manually or import it from an excel sheet.

To access the next PVT table click on the arrow next to the word Table 1. After entering the data click on “done” and go back to the fluid properties dialogue box and check “use tables”, after you are done click on “done” to exit the fluid properties dialogue box. General In the system options first choose in the reservoir fluid field “General” 1 2 Then open the pvt fluid properties window, you will find three tabs: Oil, Condensate, and Water

In the oil tab enter the same data you used to enter before, and the same options of tables and matching and controlled miscibility exist. 3 In the condensate tab you will have to enter:

Separator pressure

Separator temperature

Separator GOR

Separator gas gravity

Tank GOR

Tank gas gravity

Condensate gravity

Dewpoint at reservoir temperature

Reservoir temperature

Reservoir pressure

Mole percentage H2S

Mole percentage CO2

Mole percentage N2

Here we also have the same options to use matching or from tables directly exactly like mentioned before in oil 4 If we choose tables we will have to enter the data in the table or import it and we can also add more than one table with the variable being the temperature and the dew point 5 In the water tab you will have to enter just water salinity And we can also use tables to input the data or import it 6 Checking the PVT Calculation To check the PVT data entered choose calculator from the PVT menu

Enter the range of temperatures and pressures you want to view the data of and the steps you want in between the intervals

After that click on calc again to show the results, and to view a plot of the results click on plot, and to change the variables that are plotted click on variables. Oil Decline Curve Analysis Defining the Fluid From the tools select decline curve

Open options to define the reservoir fluid and production history method:

By tank: this requires to enter the history of a single well or the reservoir as a whole

By well: this is a well by well option that requires to enter the production history for each well or group of wells Entering the Production History Click on the "Input" button then enter the following:

Well name

Choose the decline type:hyperbolic, harmonic or exponential

Production start date

Abandonment rate (optional):the minimum production rate for the well

Decline periods

Production history

After that click on match and then regress to match the decline curve. Setting up the prediction Open prediction setup

Enter prediction start and end dates along with the abandonment rate Setting Reporting Schedule Set the production schedule to automatic, this option tells the program to display a calculation every 90 days.

press done to run the prediction Running the prediction Click on "calc" to start the prediction

You can also plot the results by using the plot tool Production data can be fitted to Hyperbolic, Exponential pr Harmonic declines. These can be then extrapolated into the future generation of forecasts. This tool analyses the decline of production of a well or reservoir versus time. It can be used for production history matching and/or production prediction. Monte Carlo Simulation This tool enables the user to perform statistical evaluations of reserves. Distributions can be assigned to variables like porosity or thickness of the reservoir and the program will generate the range of probabilities associated with a reserves range. This technique is used to evaluate the hydrocarbons in place. Defining the Primary Fluid of the Reservoir From the tools select monte carlo

Go to options

Next step is supposed to be defining the PVT but this has already been explained before in this lecture. Entering Reservoir Parameters From input chose "distribution"

Input the following:

Number of cases: the number of segments of equal probability that the distribution will be divided into

Histogram steps: the number of steps that will be plotted on the histogram

Temperature

Reservoir initial pressure

Chose the method to be used in calculating the pore volume

Select the appropriate distribution type for each reservoir parameter, and enter the values required. Starting the Calculation Click on "Calculate" under calculation

Then press on "calc" Viewing 90,50,10 P's In the calculation window click on "Results"

To view the calculations graphically on a histogram click on "plot" 1 D Model Introduction This model uses the classic buckley leveret tool of predicting breakthrough times and saturations in a water flooding scenario

This model assumes:

A rectangular reservoir with a injector well at one end and a producer on the other end

Both the producer and injector well are perforated across the entire formation thickness

The injection rate is constant

The fluids are immiscible

The displacement is considered as incompressible

The saturation distribution is uniform across the width of the reservoir

Linear flow lines are assumed, even in the vicinity of the well

Capillary pressures are neglected

The reservoir is divided into cells, a time step is computed according to the injection rate and the size of the reservoir, at each time step and each cell MBAL claulates:

Water gas and oil relative K’s based on cell’s saturations

Fractional flow of each fluid based on their relative k’s

Cell production into the next cell based on fractional flow’s

New cells saturation based on the production Defining the Primary Fluid Open system options to define the primary fluid in the reservoir, in this tool only oil is available Inputting Reservoir Injection & Fluid Properties Open input reservoir parameters to input reservoir injection and fluid properties, Input:Injection fluid: water or gas

Injection rate: in STB/day

Start of injection

Oil density

Oil viscosity

Oil FVF

Solution GOR: used in gas injection only

Water/gas density

Water/gas viscosity

Water/gas FVF

Reservoir length

Reservoir width

Reservoir height

Oil/water contact or gas/oil contact

Dip angle

Permeability

Porosity

Connate water

Cut-off water cut or GOR: value at which MBAL will end the simulation

Number of cells: maximum 500 Inputting Relative Permeability’s Corey Functions Tables Open input relative permeability’s to access the relative permeability’s

Choose from where to get the relative permeability’s: corey functions or user defined input tables

After defining by using any of the methods, you can plot the relative permeability curve to check the quality of the data If you choose corey functions, enter the following:

Residual saturations: the connate saturation of the water phase and the residual saturation of the oil phase for water flooding.

End points: is the relative k’s at its maximum saturation for each phase.

Corey exponent: defines the shape of relative permeability curve between the residual saturation and maximum saturation for each phase. If you choose from tables:

Enter both data for Sw and Krw along with So and Kro Running Simulation Now we can run a simulation, by clicking on calculations and then run simulation, then press calculate again. A graph like this will show. For a complete output click on output results. Plotting Calculated Variables To plot the output variables against each other we can use the plot button, then click on variables to choose between any two variables. Multi Layer Relative Permeability’s averaging for different layers can be done using this tool. The purpose of this tool is to generate pseudo relative permeability curves for multi-layer reservoir using immiscible displacement. These can then be used by other tools in MBAL such as Material Balance. Specifying Reservoir and Injected Fluid Choose from tools the multilayer tool and then click on options to define the following:

Initial reservoir fluid type

Injected fluid

Calculation method: buckley-leverett, stiles, communication, simple

After that the PVT description is entered as shown before Reservoir Description To specify the reservoir parameters click input reservoir parameters and enter the following:

Reservoir initial pressure

Reservoir temperature

Reservoir dip angle

Cut-off water cut or GOR: value at which MBAL will end the simulation

Injection rate

Reservoir width Layer Description Basic Layer Description Choose input layer properties to enter the layer properties, enter each layers:

Thickness

Porosity

Permeability

Water break saturation Defining each layers Relative Permeability Curve Click on rel perm to enter the Relative permeability curve

Choose from where to get the relative permeability’s: corey functions or user defined input tables

After defining by using any of the methods, you can plot the relative permeability curve to check the quality of the data. Corey Functions If you choose corey functions, enter the following:

Residual saturations: the connate saturation of the water phase and the residual saturation of the oil phase for water flooding.

End points: is the relative k’s at its maximum saturation for each phase.

Corey exponent: defines the shape of relative permeability curve between the residual saturation and maximum saturation for each phase. Tables If you choose from tables:

Enter both data for Sw and Krw along with So and Kro Running Simulation Now we can run a simulation, by clicking on calculations and then run simulation, for a complete output click on output results, and these variables can be plotted against each other using the plot button. Reservoir Allocation Introduction When a well is producing from multiple layers, it is essential for an engineer to know how much each layer has contributed to the total production. MBAL improves allocation by allowing the user to enter IPR data for each layer and calculates the allocation by taking the rate of depletion into account as well. Crossflow is also accounted for in the model, as well as different start/finish times for each well. Impurities are also tracked and can provide as effective measure of the quality of the underlying assumptions in the case where few data is available. Defining the Reservoir Fluid Choose from tools the reservoir allocation toolClick on options to enter the reservoir fluid type And enter if there is impurities that need to be tracked in the model for comparison with measured percentages at the end of the allocationAfter that enter the PVT data as shown befire Defining Tank Data Tank Parameters Click on input and then tank data and enter:

Tank temperature

Initial pressure

Porosity

Connate water saturation

Water compressibility

Initial gas cap

OOIP

Start of production

You can add as many tanks as you wish by clicking on the plus sign Relative Permeability Corey Functions If you choose corey functions, enter the following:

Residual saturations: the connate saturation of the water phase and the residual saturation of the oil phase for water flooding.

End points: is the relative k’s at its maximum saturation for each phase.

Corey exponent: defines the shape of relative permeability curve between the residual saturation and maximum saturation for each phase. Tables If you choose from tables:

Enter both data for Sw and Krw along with So and Kro Click on rel perm to enter the Relative permeability curve

Choose from where to get the relative permeability’s: corey functions or user defined input tables

After that you can plot the graphs of the relative permeability's to check the quality and validity of the data. Defining Well Data Setup Choose the well type and if you want to add wells you can add by clicking on the plus sign Choose input well data to define the wells. Production History Now enter the production history by clicking on the production history tab, this can be imported from an excel sheet or entered manually Inflow Performance Now enter the inflow performance of the well

Enter the productivity index of the well Calculation Setting up allocation size Click on calculation and then setup

Set the allocation setup size to automatic Start Calculation Click on calculate and then run allocate and click on calculate to start calculating

We can use the tank result option to display the tank and results from a production allocation Comparing between Wells and layers If we want to compare between wells and layers we can use the well/layer results option to plot and compare graphs of each layer and each well Material Balance Introduction This tool incorporates the classic use of material Balance calculations for history matching through graphical methods. Detailed PVT models can be constructed for oils, gases and condensates. Furthermore, Prediction can be made with or without well models and using relative permeabilities to predict the amount of associated phase production.

Throughout the reservoir the following assumptions apply:

•Homogenous pore volume, gas cap and aquifer

•Constant temperature

•Uniform pressure distribution

•Uniform hydrocarbon saturation distribution

•Gas injection in gas cap Defining the System Choose from tools the material balance tool

Click on options to access system options box to enter the reservoir fluid type

Enter Reservoir fluid type: oil, gas, ret condensate, general

Now define the PVT as shown previously Defining the Tank Data Tank parameters Click on input tank data, choose tank parameters then enter the following:

•Tank type: oil, water

•Temperature

•Initial pressure

•Porosity

•Connate water saturation

•Water compressibility(optional): this can be entered or left empty and MBAL will extrapolate it from the PVT tables or will use an internal correlation to evaluate it

•Initial gas cap

•Initial oil in place

•Start of production date Water Influx Choose water influx

Select an aquifer model from the following:

Small pot

Schilthuis steady state

Husrt steady state

Husrt-van everdingen odeh

Hurst-van everdingen dake

Vogt wang

Fetkovich semi steady state

Fetkovich steady state

Husrt-van everdingen modified

Carter tracy

Enter the following:

Aquifer system: radial aquifer, linear aquifer, bottom drive aquifer

Reservoir thickness

Reservoir radius

Outer/iner radius ratio

Encroachment angle Rock Compressibility Choose Rock Compress.

Choose from the following:

From Correlation: MBAL will use an internal correlation to evaluate the compressibility as a function of the porosity

Variable vs Pressure: you can enter rock compressibility values that vary with pressure, compressibility can be defined on original volume or on tangent

User defined: the formation compressibility must be entered and MBAL will assume that the compressibility does not change with pressure

None: if there is no rock compressibility Rock Compaction Choose rock compaction

Check the Enable Model box

Check the Reversible box: if this option is not checked the pore volume will not increase back to the original volume if the reservoir re-pressurises

Enter in the table the Tank pressure and the Compaction factor corresponding to it Relative Permeability Tables If you choose from tables:

Enter both data for Sw and Krw along with So and Kro and Sg and Krg Corey Functions If you choose corey functions, enter the following:

Residual saturations: the connate saturation of the water phase and the residual saturation of the oil phase for water flooding.

End points: is the relative k’s at its maximum saturation for each phase.

Corey exponent: defines the shape of relative permeability curve between the residual saturation and maximum saturation for each phase. Click on rel perm to enter the Relative permeability curve

Choose from where to get the relative permeability’s: corey functions or user defined input tables

After that you can plot the graphs of the relative permeability's to check the quality and validity of the data. Entering Tank Production History Choose production history

Then enter the following data:

Date

Reservoir pressure

Cumulative oil production

Cumulative gas production

Cumulative water production

Cumulative gas injected

Cumulative water injected

These data can be imported from an excel sheet History Matching Viewing History Matching Plots Click on history matching and then all to view the history matching plots Activating the Regression Analysis In the history matching plots click on the analytical method plot, then click on regression to match the model with the measured data in the analytical method plot.

Select the parameters with the least trusted or the ones for which values were assumed rather than measured, then click on calc to start the regression.

The values are observed on the right hand side, if they are satisfying, then the values can be used in the model by clicking on the arrow beside Best fit.

After that the history match plots are re plotted to see if the plots are satisfactory or not. Checking the History Match using Simulation Click on history matching, then choose run simulation and then click on “calc” to start the simulation.

After the simulation is calculated, click on plot to view the pressure vs time plotted for both simulation and history data, if both curves are overlapping, then this is a good history match. Matching Relative Permeabilities Fractional flow curves are created to match relative permeabilities.

Click on History matching then choose Fw matching

After the fractional flow curves are plotted, the regression tool is chosen to regress the available historical data in order to fit the fractional flow curve, this will create a set of rel perm curves that will be used to predict the fractional flow of water. Prediction Prediction With No Wells Prediction Setup Click on production Prediction and then prediction setup

Choose Predict Profile from Production Schedule (No Wells)

And tick Use Relative Permeabilities Production Constrains Click on Production prediction then choose production and constrains

The oil production desired is entered in the constrains along with the start date

This production will be kept constant throughout the prediction, until the reservoir does not have enough energy to support it. Reporting Schedule Click on Production Prediction and then choose reporting schedule, then choose one of the following settings:

Automatic: MBAL displays a calculation every 90 days

User List: a list of dates can be set in the table

User Defined: any date increment in days, weeks, months or years can be defined

Click on Done Running Prediction Click on production prediction, then run prediction, in the window that appears click on calc to start the calculation. Plotting the Prediction In the production prediction window click on plot and then choose variables to choose what variebles you want to plot vs each other. Prediction Using a Well Prediction Setup Go to the prediction setup window by clicking on production prediction and then production setup

Choose from the drop down menu “production profile using well models”

Then click done Entering the Constrains Click on production prediction then click production and constrains

The well head pressure now needs to be specified in the constrains

Now click on done Defining the Well Click on Production prediction and choose well type definition

Add a well by clicking on the plus sign next to well

Choose from the drop down menu the well type and then click on next Setup Add a well by clicking on the plus sign next to well

Choose from the drop down menu the well type and then click on next Defining Inflow Performance After clicking next now you can choose to enter the inflow performance data using IPR by clicking on match IPR

Then enter the liquid rate and the FBHP corresponding to it along with the reservoir pressure and watercut, then click on calc Defining Abandonment Constrains Click on More inflow and enter the constrains you want if necessary Defining the Outflow Performance In the well input data window click on outflow performance

And enter the outflow performance data which is the liquid rate and the FBHP for every well head pressure, water cut, and GOR.

Then click done and done Setting well Schedule Click on production prediction then well schedule

Enter the well opening or closing time, the number of wells and the well name Reporting Schedule Click on Production Prediction and then choose reporting schedule, then choose one of the following settings:

Automatic: MBAL displays a calculation every 90 days

User List: a list of dates can be set in the table

User Defined: any date increment in days, weeks, months or years can be defined

Click on Done Running Prediction Click on production prediction, then run prediction, in the window that appears click on calc to start the calculation. Plotting the Prediction In the production prediction window click on plot and then choose variables to choose what variebles you want to plot vs each other. Predicting the Number of Well Needed to Achieve Target Rate Running Prediction Click on production prediction, then run prediction, in the window that appears click on calc to start the calculation.

As shown below the number of wells is shown Plotting the Prediction In the production prediction window click on plot and then choose variables to choose what variebles you want to plot vs each other. Setting the Prediction Click on production prediction and then choose prediction setup

Choose from the drop down menu “calculate number of wells to achieve target rate”

Choose the target type

Then click done Entering the Constrains This option need a defined well type to add as many wells of this type as needed to achieve the specified target

Click on production prediction and then choose production constrains

specifying the target rates and the well head pressure along with the starting date

click done Potential Well Schedule In this section we specify how many wells are allowed to be drilled and the minimum drill time needed to drill that well and the type of each well

Click on production prediction and choose potential well schedule, then enter the mentioned data and then click done Matching of Water Cuts In order to quantify exactly how much difference there is in terms of actual water cut in the history and the match of the model. To do that a prediction of history is done where the production history of oil is fixed and the production of water and gas will be calculated based on the fractional flow curves and then compared to the historical production. Setting up the Prediction Click on production Prediction and then prediction setup

Choose Predict Profile from Production Schedule (No Wells)

And tick Use Relative Permeabilities

Set the prediction start to start of production

Set the prediction finish to end of production history Historical production Volumes The historical production volumes of oil have to be extracted from the tank

Click on production prediction then choose production constrains then click on copy to copy the historical rates Reporting Schedule Click on Production Prediction and then choose reporting schedule, then choose one of the following settings:

Automatic: MBAL displays a calculation every 90 days

User List: a list of dates can be set in the table

User Defined: any date increment in days, weeks, months or years can be defined

Click on Done Running Prediction Click on production prediction, then run prediction, in the window that appears click on calc to start the calculation. Plotting the Prediction In the production prediction window click on plot and then choose variables to choose what variables you want to plot vs each other. Select both history and prediction steams to be plotted together, to see if there is a good agreement between the data and the forecast or not, if yes then the model is ready for prediction Introduction MBAL is a package made up of various tools designed to help engineers gain a better understanding of reservoir behavior and perform predictions. The various tools available in MBAL are:

Material balance

Reservoir Allocation

Monte Carlo Volumetric

Decline Curve Analysis

1-D Model (Buckley-Leverett)

Multi-Layer (relative permeability averaging)

This presentation explains the basic procedures to follow in order to set-up an MBAL Oil model. This presentation focuses on how to use the various program features as analytical tools to solve engineering problems. Unfortunately this presentation only focuses on Oil reservoirs, gas and condensate reservoirs are not explained in this guide. This Presentation is done by:

Mohamed Ibrahim Balaha

Under the supervision of:

Dr Atia M Atia

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