rubis guided session #3 · rubis guided session #3 a01 • introduction this chapter is an...

Ecrin v4.20 - Doc v4.20.01 - © KAPPA 1988-2011 Rubis Guided Session #3 • RubGS03 - 1/22

Rubis Guided Session #3

A01 • Introduction This chapter is an illustration of some more advanced features of Rubis, in which several waterflood scenarios will be simulated and compared. It is assumed that the basic functionalities shown in the first guided session are mastered. Like the previous guided sessions, this exercise does not pretend to be realistic but to show Rubis features. Key functionalities presented: multi-run document, comparison of results between runs, time dependent skin, delayed perforation openings, creation of an aquifer, vertical anisotropy, output and use of global results. B01 • Creating the Base Case Scenario B01.1 • PVT and Reservoir Geometry Start Ecrin and make Rubis the active module. Create a new document. In the ‘Reservoir – Field infos’ dialog change the reference date to January 15th, 2009 and the default end date to December 31st, 2019:

Fig. B01.1 • ‘Reservoir – Field Infos’ dialog


Rename the current run by clicking on in the run toolbar, and set the run name to ‘Base’. Next click on the PVT icon and set the fluid type to Saturated Oil with Water – we will once again skip the definition of the various correlations, and keep all available defaults:

Fig. B01.2 • PVT definition

Click on OK to validate. Select ‘Geometry’:

Change the number of layers to 4:

Rename the layers, from top to bottom: ‘Top’, ‘Middle 1’, ‘Middle 2’, ‘Bottom’:

Change the top horizon to ‘Data Set’ and click

on to input the corresponding data:

In the first tab of the next dialog click on to resize the table to 5 lines. Manually enter the following data points:


Move to the ‘Interpolation’ tab and change the interpolation method to ‘Inverse Distance Weighting’, with an exponent of 4:

Click on OK to validate. Then in turn set the ‘Middle 2’ layer thickness type to ‘Data Set’, and

click on . Use the pick option

( ) to set a thickness of 50 ft in the South-West and 3 ft in the North-East:

Set the ‘Top layer’ thickness to 50 ft, the ‘Middle 1’ layer thickness to 20 ft and the ‘Bottom layer’ thickness to 21 ft:

The final display of the Reservoir – Geometry should be as shown below:

Fig. B01.3 • Final display of the ‘Reservoir – Geometry’ dialog

Click on OK to validate the new geometry.

Ecrin v4.20 - Doc v4.20.01 - © KAPPA 1988-2011 Rubis Guided Session #3 • RubGS03 - 4/22 B01.2 • Reservoir Properties Let us now define the reservoir properties (petrophysics, KrPc, initial state). Click on ‘Properties’ in the ‘Simulation’ page to edit the ‘Reservoir – Properties’ dialog:

Change the reservoir type to ‘Layered’:

In the assignment table located below the reservoir type, select the two lowest cells:

Click on to create a new property set called ‘Lower zone’:

Add vertical anisotropy to the petrophysics of this property set by checking the ‘Vertical anisotropy’ box. Change k to 25 md, kv/kh to 0.1 and the leakage to 0.01 – this last parameter describes the layer-to-layer permeability reduction:

Edit the Default property set by selecting it in the assignment grid: vertical anisotropy is also checked here, as it is a global reservoir property. However we may change the anisotropy ratio itself locally: set it to 0.05, and change k to 100 md, Phi to 0.15, and the leakage factor to 0.01:

The reservoir petrophysics are now – quickly – defined. To finish, click on the ‘Initial State’ button to enter the reservoir initial fluid levels, and in the following dialog change the GOC to 5940 ft, the WOC to 6065 ft and the reference initial pressure to 4000 psia:


Fig. B01.4 • Initial State dialog

Click on OK to validate, and exit the ‘Reservoir – Properties’ dialog. We do not redefine the KrPc as we will work with default curves and end-points. Before moving on with the wells, edit the reservoir contour properties by double-clicking on it in the 2DMap – the Field contour dialog will show up. The last tab of this dialog displays the reservoir boundary conditions:

Fig. B01.5 • Reservoir boundary conditions


Click on to view all contour segments at once in the table (each segment carrying a number visible on the 2DMap):

Select the table cell on the ‘Bottom’ line and column ‘4’ – as you can check on the 2DMap the segment ‘4’ is the western boundary:

Change the cell type to aquifer – the cell will then turn blue:

Edit the aquifer settings by clicking on . Change the aquifer type to ‘Numerical’, and set the aquifer volume to 1500 MMSTB, the permeability k to 15 md:

Click on OK to validate: the reservoir is now connected to an aquifer on its bottom – western boundary. B01.3 • Creating the Wells We will now define a 5-spot pattern consisting of four water injectors located in the corners and a producer in the center.


Using the option in the 2DMap toolbar, create five vertical wells approximately located as shown opposite – the center well first, then the four corners one:

Click on the ‘Wells’ button in the Simulation page to edit the ‘Reservoir – Wells’ dialog:

Fig. B01.6 • ‘Reservoir – Wells’ dialog

Rename the five wells as follows: ‘Producer’ for the center well, and ‘Inj’ followed by the spatial location for the other wells:


Edit the producer geometry by selecting it in the table and clicking on the ‘Geometry’ icon. In the ‘Producer – Geometry’ dialog, reset X and Y to 0 ft:

Then move to the ‘Cross-Section View’ and click on the Adjust Well trajectory button

( ) to correct the well path and make it intersect the entire reservoir:

Repeat the same operation on the four injectors – manual modification of the coordinates and trajectory correction – with the following coordinates:

Well X (ft) Y (ft) Inj NW -4500 4500 Inj NE 4500 4500 Inj SE 4500 -4500 Inj SW -4500 -4500

B01.4 • Well Perforations Back to the ‘Reservoir – Wells’ dialog select the Producer well in the table and click on ‘Perforations’. In the ‘Producer – Perforations’ dialog move to the ‘Cross-Section View’ tab and

use the ‘Create new perforation’ button ( ) to create two perforations as shown below – the first perforation in the ‘Middle 2’ layer (green), and the second perforation across the two top layers:


Fig. B01.7 • Creating perforations for the Producer well

In turn, select each perforation and click on to adjust their lengths to the layers they intersect. In the end, both perforations should be visually joined:

Move now to the ‘Perforations’ tab and set the opening time of the top perforation to January 15th, 2020 by checking the box in the ‘Opening time’ column and setting the right date (in practice, we are making sure that the top perforation will never be opened during this run). Set the skin of the lower perforation to +3:

Click on OK to validate the changes – perforations are now defined for the Producer well. Let us now perforate the four injectors:


Select each well in the ‘Reservoir – Wells’ table:

Click on the ‘Perforations’ button:

In the following dialog, move to the ‘Cross-

Section View’ tab and using create a perforation in the bottom layer:

Click on to have the perforation entirely intersect the layer:

B01.5 • Well Controls We will not use flow correlations to compute the pressure drop along the wellbores and rely on a simple hydrostatic computation of the pressure gradient instead. As a result, we do not need to define nor use a wellbore model for any of the wells. But we need to describe the history schedule of each well. In the ‘Reservoir – Wells’ dialog, select the Producer and click on ‘Controls’ to edit the ‘Producer – Controls’ dialog. Create a downhole pressure target (‘P (BH)’) of 3500 psia, controlled by a total bottomhole rate constraint (‘Q Tot (BH)’) of 10000 B/D:

Click on in the ‘Conditional constraints’ window to activate the constraint that closes the well when the total bottomhole rate reaches the zero value. Now, select each injector well in turn, change its mode to Injector and define a constant bottomhole pressure target (‘P (BH)’) of 4000 psia, controlled by a maximum bottomhole rate constraint (‘Q Wat (BH)’) of -10000 B/D. Add a conditional constraint for each well.

Once all targets and constraints have been defined over all wells, you may use the well selection box located in the bottom left of the dialog to compare ‘All’ controls from all wells in the same table:


Fig. B01.8 • Well controls

Click on OK to validate all changes – and exit the ‘Reservoir – Wells’ dialog. B01.6 • Viewing the Reservoir Geometry Before the simulation, we can visually check the current definitions. Draw two cross-sections

( ) in the 2DMap, the first one crossing the reservoir from SW to NE and the second one from NW to SE – make sure that the cross-sections pass through the wells:

Fig. B01.9 • Cross-sections drawn in the 2DMap


Double click on each cross-section to view it and click on to visualize the fluid contacts:

Fig. B01.10 • SW to NE cross-section view, layers (left) and fluid contacts (right)

Fig. B01.11 • NW to SE cross-section view, layers (left) and fluid contacts (right)

Ecrin v4.20 - Doc v4.20.01 - © KAPPA 1988-2011 Rubis Guided Session #3 • RubGS03 - 13/22 B02 • Simulating the Base Case Scenario B02.1 • Grid Construction and Run Settings Click on the ‘Grid’ button in the ‘Simulation’ page and accept all default settings to go ahead with grid construction:

Fig. B02.1 • After grid construction

Edit the ‘Simulation – Run Settings’ dialog. In the first tab (‘Time Settings’), check that the simulation end date is set to December 31st, 2019:

Move now to the ‘Results’ tab, and change the ‘time period’ of the ‘Field Results’ to 150 days:

In the same tab, specify that we wish to output the reservoir total oil cumulative production and the global water influx (water coming from the aquifer) by checking the ‘Qo’ and ‘Water Influx’ nodes under the ‘Global results’:

Click on OK to validate all changes.

Ecrin v4.20 - Doc v4.20.01 - © KAPPA 1988-2011 Rubis Guided Session #3 • RubGS03 - 14/22 B02.2 • Initialization and Simulation Click on ‘Initialize’ and ‘Simulate’ to perform the Rubis simulation:

Fig. B02.2 • After numerical simulation

When the run is completed, maximize the ‘Global Results’ plot and double-click on the ‘Cumulative’ view to check the field total cumulative oil production:

Fig. B02.3 • Global results, field total oil cumulative production

Ecrin v4.20 - Doc v4.20.01 - © KAPPA 1988-2011 Rubis Guided Session #3 • RubGS03 - 15/22 In the same plot maximize the ‘Influx’ view to visualize the water influx coming from the aquifer into the reservoir – a total of approximately 0.3 MMSTB of water has invaded the reservoir after 11 years of production:

Fig. B02.4 • Global results, water influx vs. time

Maximize the 2D Geometry plot, choose ‘Sw’ as the property to be displayed and click on in the plot toolbar to change the current display settings:

Fig. B02.5 • Property map display settings

Ecrin v4.20 - Doc v4.20.01 - © KAPPA 1988-2011 Rubis Guided Session #3 • RubGS03 - 16/22 In the above, set the display type to ‘gradient’ and uncheck the ‘Show grid’ box. Click on OK to validate the changes.

Click on the Select depth button ( ), check the stratigraphic depth option and select the Middle 1 layer. Then compare the first and last water saturation fields by navigating with the

appropriate buttons in the time navigation toolbar ( and ):

Fig. B02.6 • Water saturation fields in the Middle 1 layer, in 2009 (left) and end-2019 (right).

A small advance of waterfront is noted. Maximize the cross-section plot corresponding to the NW-SE cross-section, display the saturation fields (ternary display) and once again compare the first and last field outputs to check the evolution of the water front and the gas saturation decrease in the upper gas cap because of the recompression of the reservoir:

Fig. B02.7 • Saturations ternary display in the NW-SE cross-section,

in 2009 (left) end end-2019 (right)

Ecrin v4.20 - Doc v4.20.01 - © KAPPA 1988-2011 Rubis Guided Session #3 • RubGS03 - 17/22 C01 • Running Alternative Scenarios C01.1 • Opening the Producer Top Perforation We will evaluate now how the oil production is affected if the (always closed so far) producer

top perforation is opened during the life of the reservoir. First, click on in the run toolbar to create a new run by copy of the Base one – name this run ‘Perf’:

Fig. C01.1 • Creating the ‘Perf’ run

In this new run, edit the wells by clicking on the ‘Wells’ button in the ‘Simulation’ page. Select the producer and click on ‘Perforations’, then change the top perforation opening time from January 15th, 2020 to January 18th, 2014:

Fig. C01.2 • Top perforation opening time, before (top) and after (bottom) the changes

Edit the producer controls, and click twice on the Add button to add two more lines in the grid:

Change the starting dates of the two new controls to January 15th, 2014 and January 18th, 2014, respectively:

Ecrin v4.20 - Doc v4.20.01 - © KAPPA 1988-2011 Rubis Guided Session #3 • RubGS03 - 18/22 Specify that the target of the second control is a shut-in (‘Q Tot (BH)’=0, no constraint), and set the third and last control to be identical to the first one (target of type ‘P (BH)’ = 3500 psia, with a constraint ‘Q Tot (BH)’ = 10000 B/D) – the shut-in is inserted to take into account the time necessary to perform the perforation job:

Click on OK to validate all changes. We do not need to rebuild the grid, as no modification was made in the reservoir geometry. Visit the ‘Simulation – Run Settings’ dialog to confirm the various options copied from the previous run, and proceed with the simulation. When it is completed, maximize the Cumulative view in the Global Results plot to check that the total oil cumulative production is now slightly higher than the base case:

Fig. C01.2 • Global results, field total oil cumulative production of the ‘Perf’ run

C01.2 • Improving the Producer Skin Let us now see what happens if the opening of the producer top perforation is replaced by an improvement of the middle perforation skin – as the result of a fracturation job, for instance. Create another run called ‘Frac’ by copy of the ‘Base’ run:


Fig. C01.3 • Creating the ‘Frac’ run

In this new run, edit the wells by clicking on the ‘Wells’ button in the ‘Simulation’ page. Select the producer and click on ‘Perforations’, then move to the ‘Completion’ tab:

Fig. C01.4 • Editing the completion of the producer perforations

In this tab, select the lowest perforation

(Perf#2) and click on to edit its skin value(s):

In the second line of this table, enter -1 for the skin value and change the corresponding t@start to January 20th, 2014:

Click on OK to validate: in the above, we have set that the Perf #2 skin will switch to -1 after January 20th, 2014. Before this date the skin value will remain at its default value recalled in the first line of the table: skin = 3.

Ecrin v4.20 - Doc v4.20.01 - © KAPPA 1988-2011 Rubis Guided Session #3 • RubGS03 - 20/22 Let us now edit the Producer controls and, similarly to the previous case, model the fracturation job as a shut-in just preceding the completion change: Click on ‘Add’ twice to add two new controls to the history schedule:

Change the starting dates of the two new controls to January 15th, 2014 and January 20th, 2014, respectively:

Specify that the target of the second control is a shut-in (‘Q Tot (BH)=0’, no constraint), and set the third and last control to be identical to the first one (target of type ‘P (BH)’ = 3500 psia, with a constraint ‘Q Tot (BH)’ = 10000 B/D):

Click on OK to validate all changes. Rebuild the grid (the grid needs to be rebuilt here because the well minimum skin has changed) and re-simulate the problem. Observe the cumulative oil production. C02 • Comparing the Different Scenarios We will now compare the output of the different scenarios in the Browser tab of Rubis – click

on the icon to display that tab:


Fig. C01.5 • Rubis browser tab

Expand the various browser nodes as displayed on the right and select the ‘qo (surface)’ node of the ‘Producer’ well in the ‘Simulation Output’ of the ‘Base’ simulation. Drag and drop it to the ‘Data store’, in order to create a copy of this result gauge. Proceed similarly to drop the ‘qo (surface)’ simulated gauges of the ‘Perf’ and ‘Frac’ runs into the ‘Data store’. The ‘Surface Rate’ node of the ‘Data store’ will now contain the 3 gauges:

In the Data store select the ‘qo (surface) – Base – Producer’ and edit its properties with the

right-hand side toolbar button. Change its screen color to red in the ‘Aspect’ tab. Change the screen color of the respective surface rate nodes to blue and green, for ‘Perf’ and ‘Frac’

runs. Select the main ‘Data store – Surface rate’ container and click on to visualize all curves graphically:


Fig. C01.6 • Comparing the Producer surface pressures simulated in all scenarios

Repeat the same operations with the total reservoir oil cumulative production (Qo node contained in the Global Results container of each run), to obtain the final display:

Fig. C01.7 • Comparing the total cumulative oil production simulated in all scenarios

As can be seen above, the ‘Frac’ scenario results in a production increase of approximately 193,000 STB, while the ‘Perf’ scenario leads to a lower production gain of 112,000 STB.

rubis guided session #3 · rubis guided session #3 a01 • introduction this chapter is an...

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