Eclipse中煤层气模拟实例

ECLIPSE CBM Template
Workshop
Exercise 1 – Single-Well, Single Layer (3)
Introduction (3)
Exercise1 - Stages (3)
Creating a template case in ECLIPSE Office (4)
Model Definition (5)
Reservoir Description (6)
Wells (7)
Production (8)
Fluid Properties (10)
Run and Results (10)
Exercise 2 – Single-Well, Single Layer, Gas-Water (12)
Introduction (12)
Stages (12)
Restoring a template model (13)
Model Definition (13)
Reservoir Description (13)
Fluid Properties (14)
Generating the Model (15)
Running Simulation & Results (16)
Sensitivity to Gridding Controls (17)
Exercise 3 – Sensitivity to Reservoir Conditions (25)
Introduction (25)
Stages (25)
Customizing Reports (26)
Creating a New Project (26)
Sensitivity to Initial Conditions (27)
Sensitivity to Rock Properties (29)
Sensitivity to Fluid Properties (32)
Exercise 4 – Well Spacing Optimization (41)
Introduction (41)
Stages (41)
Problem Description (42)
Building a Quarter Five-Spot CBM template model (42)
Comparing Pattern Recovery Factors (46)
Creating Reports (47)
Evaluating Net Present Value (49)
Exercise 5 – Enhanced Production with Fractured wells and Horizontal Wells - Interference (53)
Introduction (53)
Stages (53)
Single Vertical Well Model (54)
Two Vertical Well Model (56)
Hydraulic Fractured well (61)
Horizontal Well (64)
Exercise 6 – Optimizing Development in a Dipping Reservoir (66)
Introduction (66)
Stages (66)
Building a 4-vertical well model (66)
Sensitivity to Workovers Timing (68)
Exercise 7 – Hydraulic Fractures and Zonal Isolation (71)
Introduction (71)
Stages (71)
Creating a Single Coal Seam Model (72)
Analyzing the Hydraulic Fracture Impact on Production (73)
Creating a 3-Layer Sand-Shale-Coal Model (75)
Analyzing the Impact of the Failed Zonal-Isolation on Production (76)
Exercise 1 – Single-Well, Single Layer
Introduction
The objective of the following exercise is to familiarize the user with the main features and environment of the Coal Bed Methane template. The exercise demonstrates a step-by-step procedure on how to build and run simulation on a single-layer, single-well production scenario with dry gas as the only phase present. Stages
Creating a template case in ECLIPSE Office (4)
Model Definition (5)
Reservoir Description (6)
Layers Definition (6)
Rock Properties Definition (6)
Initial Conditions Definition (7)
Wells (7)
Production (8)
Perforation Definition (8)
Production Constraint Definition (9)
Fluid Properties (10)
PVT Correlations (10)
Run and Results (10)
Creating a template case in ECLIPSE Office
1. In your Windows Explorer, create a new folder. Rename the folder CBM. Create another folder
under CBM and rename it Exercise1.
2. From the ECLIPSE Simulation Software Launcher, start Office and select Exercise1 as the startup
directory. The main ECLIPSE office window will pop up.
3. As shown below, create a new project by selecting File | New Project…Give it the file name
1well-1layer and click Open.
4. This will create a parent project under which a number of children scenarios called cases can be
created. As shown below, we will create a CBM template case from this parent case. Right click
on the case 1well-1layer and select Add Template Case.
5. In the Template model selection panel, select Coalbed Methane as the Template Model type, name
the case Dry-Gas and select Field Units as shown below.
6. Click OK. The Coalbed Methane Modeling Tool general panel will pop up, as shown below:
Model Definition
1. Give a title name to the current case: Single-well Single-layer Dry Gas
2. Define the general time framework controls:
• Simulation start date: 1 Jan 2004
• Simulation end date: 1 Dec 2004
• Reporting frequency: 1 month
3. Request that only dry gas be present in the run, under the Phases drop-down menu in the Model
Parameters. Leave the other options unchecked for now.
4. Click Apply.
5. In the Workflow Column, select Reservoir Description to jump to the Reservoir Characterization
input tab.
Reservoir Description
Layers Definition
The model contains a single coal seam. We will now input the general dimensions of that layer.
1. Name the layer Layer1 and its rock type Coal1.
2. Set the top left and right faces to 1000 ft deep.
3. Set the horizontal displacement to 0 ft. (This entry will be ignored here since the model contains
only one layer).
4. Set the thickness to 30 ft.
5. Set the length to 2000 ft
6. Set the width to 800 ft
7. Click Apply.
The Layers table should look as shown below:
8. Click on Next Page to jump to the Rock Properties input tab.
Rock Properties Definition
By default, properties of the RESERVOIR rock show up in the Rock Properties tab. If properties for no other rock types are specified here, the template will assume RESERVOIR to be the default rock type used for the run.
Another rock type (Coal1) was defined in the previous step; we will now characterize Coal1’s cleat system:
1. Under RESERVOIR, add a new line for Coal1.
2. Set the fracture porosity to 0.01
3. Set the horizontal permeability to 20 mD and the vertical permeability to 2 mD.
4. Set the coal’s compressibility to 1e-6 psi-1
5. Click Apply.
The Rock Properties table should now look as shown below:
6. Click on Next Page to jump to the Initial Conditions input tab.
Initial Conditions Definition
1. Set the initial pressure to 300 psi at a reference datum depth of 1000 ft.
2. Leave the Coal Gas Concentration space blank. This requests that the initial coal gas concentration
be computed automatically from the Langmuir Isotherm gas desorption curve defined later in the exercise.
3. Click Apply.
We assume in this model the absence of aquifer and hydraulic fractures. The last two tabs may therefore be skipped. In the Workflow column, select Wells to jump to the well definition panel.
Wells
By default, the Field space in the wells tab should show that one layer (Layer1) has been defined, but that there aren’t any wells declared yet. We will now add a new vertical well to the model.
1. In the main Wells column, highlight and right-click on the Field space. Select Create Well.
2. Name the new well V1. A new well branch will be added under Field.
3. Highlight V1 and change the drilled hole diameter to 24 in. Click once on Insert Row to add a row
to the table where V1’s deviation will be specified.
Since V1 is vertical, only two rows for the well’s top and bottom depths are required to fully describe the deviation. The deviation points areal coordinates and depths are referenced to the local normal coordinate system of origin (0,0,0) created at the layer definition stage.
4. Give V1 respective X and Y positions of 500 ft, and a wellhead depth of 0 ft.
5. Click Apply and Insert a new row.
6. In the second row, set the depth to 1050 ft.
7. Click Apply and check that the Measured Depth Field has been updated. The Wells tab should
now look as shown:
8. In the main Template window, under the Workflow column, click on Generate Model. This will
generate a 3D representation of the information input thus far, as shown below:
9. In the Workflow column, select Production to jump to the Production and well work over
definition panel.
Production
Perforation Definition
In the Production Field, highlight the well V1 branch and observe that no events currently exist. We will
now define two sets of events for the well V1: Events defining the well’s perforation intervals as well as
events characterizing the production constraints and limits of well V1.
1. Check that well V1 has been highlighted, select Perforation V1 in the Available Events drop down
list and click on New Events to add a perforation.
2. In the perforation panel, the default date of perfarion is SOS (Start Of Simulation), 1 Jan 2004 in
this case. Leave the date defaulted.
3. Well V1 extends from 0 ft to 1050, but based on the definition of Layer1, only the section
extending from 1000 ft to 1030 ft is exposed to the reservoir. Change the Start and Stop MDs to
1000 ft and 1030 ft.
4. Click OK and observe the addition of the event under existing events, as well as a detailed
description of the selected event.
Production Constraint Definition
1. In the Available Events drop down list, select Production from V1 and click on New Events. The
Production Well Schedule Data panel will pop up.
2. Under the Well Controls tab, leave SOS as the start date for production. Change the Control Mode
to Bottom Hole Pressure (BHP), and set the target to 20 psi.
3. Jump to the Limits tab.
4. Set the limit type to Gas Rate and set the limit to 1000 Mscf/d, and set the limit to 20 psi.
5. Click on Add/Update.
6. We assume here that there are no economic limits. Click OK and observe the addition of the
production event in the list of existing events along with a detailed description.
The Template panel should now look as shown below:
7. In the main Template window, under the Workflow column, click on Generate Model. Observe
the changes in the 3D Viewer:
This shows how the rid is now refined around the perforated interval of well V1. We will see later in this tutorial the importance of grid refinements as well as how to control the refinement level.
In the Workflow column, select Fluid Properties to jump to the fluid and coal’s sorption capacity definition panel.
Fluid Properties
PVT Correlations
There is only dry gas present in this case. The properties of gas, the pressure dependent viscosity and Formation Volume Factor (B g), are computed from a correlation.
1. Set the temperature Layer1 to 100 F.
2. Leave the specific gravity of gas set to 0.7 sg_Air.
Coalbed Methane Properties
The parameters entered in is tab are used to derive the Langmuir Isotherm used to control the coal gas desorption from the coal face as a function of pressure.
Additional parameters are used to control the diffusion of gas from matrix to the fracture system where it then flows into the well.
Sensitivity of production profiles to these various parameters will be seen in later exercises.
1. Leave the parameters defaulted for now.
2. Click Apply.
Run and Results
1. Click on Run ECLIPSE.
2. When the run is finished, click on View Results. Office will generate a set of profiles resulting
from the simulation. Observe the gas production rate achieved:
3. In the Template module, click on File | Save… and save the Dry-Gas.TPM file, which can later be
used to restore the settings used in this template case.
4. Close the Template module and Close ECLIPSE Office after saving the Office project.
Exercise 2 – Single-Well, Single Layer, Gas-Water
Introduction
The previous exercise assumed only dry gas was present in the reservoir. In most cases, coal cleats are initially filled with water and this water must first be produced for the coal gas to desorb in the matrix and flow to the fracture system. This production stage is often referred to as the dewatering stage.
The objective of this exercise is to show examples of how the presence of initial water affects the gas production profile.
Stages
Restoring a template model (13)
Model Definition (13)
Reservoir Description (13)
Initial Conditions Definition (14)
Fluid Properties (14)
Relative Permeability Definition (14)
Quality-Checking the Fluid Properties (14)
Generating the Model (15)
Running Simulation & Results (16)
Sensitivity to Gridding Controls (17)
Cloning a Template Case (17)
Areal Resolution (18)
Comparing Cases Results (19)
Vertical Resolution (22)
Restoring a template model
1. In your Windows Explorer, under the CBM folder created in the previous exercise, create a new
folder named Exercise2.
2. From the ECLIPSE Simulation Software Launcher, start Office and select Exercise2 as the startup
directory.
3. As described in Exercise1, create a new project by selecting File | New Project…Name it 1well-
1layer and click Open.
4. We will now create a new CBM template case from this parent case. Right click on the case 1well-
1layer and select Add Template Case.
5. In the Template model selection panel, rather than rebuilding from scratch a new template model,
we will import the model created in Exercise1. Select Coalbed Methane as the Template Model
type, name the case Gas-Water, select Field Units and use the browser in the Start File field to
select Dry-Gas.TPM located in the Exercise1 directory, as shown below:
6. Click OK to open up the CBM Template module. Observe that the model generated in Exercise
has been restored along with all of the parameters used to define the case.
Model Definition
1. Change the case title name to: Single-well Single-layer Gas-Water
2. Leave the simulation time framework unchanged
3. Under Model Parameters, change Phases from Dry Gas to Gas & Water.
4. Click Apply.
The reservoir description remains similar to that of Exercise1 but the addition of the water phase to the model requires additional information on the initial state of the reservoir, the rock’s relative permeability to water and gas as well as the water properties at reservoir conditions.
We will now complete the model with the additional required input.
Reservoir Description
Initial Conditions Definition
1. In the Workflow column, click on Reservoir Description.
2. Select the Initial Conditions tab.
3. Observe that a new line has been added prompting the user to enter the Gas-Water Contact Depth.
Set the contact to 1020 ft.
4. Click Apply
Fluid Properties
Relative Permeability Definition
The model defined in Exercise1 featured a single-phase dry gas. The computation of the flow of gas was thus based on the absolute rock permeability defined in the Reservoir Description panel.
Here, a second phase is present, introducing the concept of relative permeability.
1. In the Workflow column, select Fluid Properties.
2. Observe that a new Rel. Perm panel has been inserted. Select it. In the Rel. Perm panel, you will
find two tabs used to specify the coefficients and end points used to derive the shape of the relative permeability to gas and water. Leave these coefficients defaulted.
Quality-Checking the Fluid Properties
Correlations are used to derive the gas viscosity and formation volume factor as well as the coal surface gas concentration as a function of pressure, and the relative permeabilities to gas and water as a function of water saturation.
1. Select the Advanced tab.
2. Click on Load Correlations.
3. Click on Plot Data…The template will pop up a window with 2D line-plots of the curves
generated from the various correlations.
4. In order to visualize other curves such as the Langmuir adsorption curve, simply click on the
selected plot and drag it to the main panel.
5. Close the window and go back to the Rel. Perm panel.
6. In the Gas tab, change the Corey Gas Factor to 1.
7. In the Water tab, change the Corey Water Factor to 1 and the water relative permeability at
residual gas saturation (K rw(S grw))to 1.
8. Click Apply.
9. In the Advanced panel, reload and plot the data from correlations. Check that the water and gas
relative permeabilities are now a linear function of saturation, as shown below:
10. Close the graph window.
Generating the Model
1. In the Workflow column, click on Generate Model.
2. In the 3D Viewer, zoom in the reservoir and note that a vertical refinement has been applied:
Running Simulation & Results
1. In the Workflow column, click on Run ECLIPSE.
2. The Log Window will indicate you when the run is finished. When it is finished, click on View
Results in the Workflow column. This will fire up the Results Viewer and load the simulation
results.
3. Take some time to analyze the Field Gas and Water Production Rates and Totals, Gas Recovery
profiles, etc…
4. In the Results Viewer, click on the 3D View icon to load and display the grid recurrent
properties in the 3D Viewer.
5. Using the top right-hand controls , animate the grid. Observe how the
Matrix Pressure distribution changes through time.
6. Using the Grid Property icon , change the displayed property from Matrix Pressure to
Fracture Water Saturation (FSWAT) and observe how water saturation decreases through time.
Sensitivity to Gridding Controls
The simulated response to reservoir changes is sensitive to the resolution of the grid used to model the
reservoir. The gridding controls available in the Simulation Controls panel can be used to generate finer or
coarser cells, giving the flexibility to automatically refine the grid around phase contact and well workovers.
Cloning a Template Case
1. In ECLIPSE Office, highlight and right-click on the Gas-Water template case. Select Add Clone
Case.
2. Name the new case: Gas-Water-Fine-Grid. This will duplicate the Gas_Water model along with all
of its settings.
We will now keep all of the pre-defined settings unchanged apart from the gridding controls, which we will modify to refine the areal resolution of the reservoir grid.
Areal Resolution
1. In the Workflow column, select Simulation Controls.
2. Keep options to grid to phase contact and well workovers checked.
3. Decrease the maximum cell size in the X and Y directions to 50 ft.
4. Click Apply and re-generate the model. Observe the resulting grid resolution in the 3D Viewer.
We would like now to decrease the cell size growth factor controlling the logarithmic refinement applied around the well perforation.
5. Decrease the X and Y Growth Factors to 1.2.
6. Click Apply and re-generate the model. Observe the resulting grid resolution in the 3D Viewer.
The grid should now look as shown below:
7. In the Workflow column, click on Run ECLIPSE.
Notice that the simulation run time has now significantly increased. This is due to the fact that ECLIPSE now needs to solve for changes in pressure and saturation over time in a much greater number of cells than in the previous model. In general, the user should find a balance between run times and solution accuracy. One way to analyze the accuracy of the results found in the Gas-Water case is to compare them with the results obtained from a higher resolution grid as the one created here.
We will now compare the production profiles from Gas-Water with Gas-Water-Fine-Grid. Comparing Cases Results
1. In the template, click on View Results to upload the Gas-Water-Fine case simulation results.
2. In the Results Viewer, click on to bring up the 3D Grid simulation results and step through
time to display the Matrix Pressure property on 01 Dec 2004.
You may notice the slightly smoother pressure change away from the well than what was obtained in the previous case. The picture below shows a comparison between the two cases. Nevertheless, the comparison of the actual profile line plots must be done in order to find out whether simulation through the finer grid differ significantly from the ones obtained earlier in the exercise.
3. Close the Results Viewer.
4. In ECLIPSE Office, select Case | Compare from the menu list.
5. In the Compare Cases panel, select Gas-Water and click on Plot.
The Result Viewer will now super-impose the gas production rates from the coarse and fine grid models. View the pressure profile. Notice that there is very little deviation of the Gas-Water profiles from the Gas-Water-Fine-Grid profiles, indicating that the resolution used in the Gas-water-Fine-Grid case does not justify the resulting higher simulation run time.
6. Following the steps previously described, clone the Gas-Water-Fine-Grid case in ECLIPSE Office
to create a case named Gas-Water-Normal-Grid.
7. In the Simulation Controls panel, check the option Regular Grid. This allows the user to specify
settings to generate a uniform cell size grid.
8. Set N x to 45, N y to 20 and N z to 10. Click Apply and generate the model.
9.
11. In ECLIPSE Office, select Case | Compare from the menu list.
cases. Click on Plot.
The Result Viewer will show how the simulated gas production profile obtained in the normal grid case starts deviating from the ones obtained with grids refined around the well bore. Generally, the early time simulation response will be a function of grid resolution near and around the wellbore.
Vertical Resolution
We have now seen the impact the choice of the grid horizontal resolution settings may have on the simulation results. Similarly, we will now analyze the importance of the vertical resolution.
1. Close the CBM Template module.
2. In ECLIPSE Office, highlight the Gas-Water template case. Using the steps described above,
clone the Gas-Water case to create the case Gas-Water-Low-Vert-Res.
3. Select the Simulation Controls. Uncheck the Grid to Phase Contact option.
4. Change the maximum cell size in the Z direction to 15 ft.
5. Generate the model. Unlike the Gas-Water case grid, which honored the Gas-Water contact, this
will create a 2 15ft-vertical cell grid, as shown below.
6. Run ECLIPSE.
7. Compare the results between Gas-Water and Gas-Water-Low-Vertical-Res.
The results clearly show the impact of a choosing a coarser vertical resolution to describe the model. The coarser resolution case shows a higher water production from the start. The bottom layer cell depths extend from 1015 ft down to 1030 ft, but the GWC was set at 1020ft and is therefore not honored by the grid. Water saturation, which should be 100% in the lower cells, is thus averaged in the coarse cells to reflect the
presence of gas between depths of 1015 ft and 1020 ft. As a result, the well mobile water the well sees in these depths range is produced from the very start of simulation.
The following picture compares a cross-sectional view of the fracture water saturation on 1 Dec 2004, in cases Gas-Water-Low-Vert-Res (left) and Gas-Water (Right).
8. Close the CBM Template module.
9. In ECLIPSE Office, highlight the Gas-Water template case. Clone the Gas-Water case to create
the case Gas-Water-High-Vert-Res.
10. Select the Simulation Controls. Make sure the option to Grid to Phase Contact has been checked.
11. Change the Z Growth Factor to 1. Click Apply.
12. Generate the model. Run ECLIPSE.
13. Compare the results from Gas-Water and Gas-Water-High-Vert-Res. Is a higher vertical resolution
necessary?
14. Following the same approach as described in this exercise, investigate how coarse the model can
be possibly made.
15. When you are finished, Save the Template model as shown in the previous exercise and close the
CBM Template module.
16. Exit ECLIPSE Office after saving your project.
Exercise 3 – Sensitivity to Reservoir Conditions
Introduction
The previous exercise consisted in building a 2-phase gas water CBM model and analyzing the impact of gridding controls on simulation results. Ideally, a grid should be fine enough to capture the main features of the reservoir, but coarse enough for simulations to complete within reasonable runtime.
The objective of the following exercise is to study in the context of a gas-water coalbed methane problem the sensitivity of production profile to the main reservoir parameters and conditions.
This exercise teaches how to create and clone template models as well as compare resulting profiles from different models.
Stages
Customizing Reports (26)
Changing ECLIPSE Office Settings (26)
Creating a New Project (26)
Sensitivity to Initial Conditions (27)
Gas-Water Contact Depth (27)
Initial Pressure (28)
Sensitivity to Rock Properties (29)
Fracture Porosity (29)
Fracture Permeability (30)
Isotropic (30)
Vertical to Horizontal Anisotropic (31)
Horizontal Anisotropic (31)
Sensitivity to Fluid Properties (32)
Reservoir Temperature (32)
Relative permeability (34)
Gas (34)
Water (37)
Coal Gas Properties (38)
Langmuir Isotherm Parameters (38)
Desorption Time (39)
Customizing Reports
The Graphics Run File (.GRF) called by ECLIPSE Office to display results from the CBM template module is the file COALBEDMETHANE.GRF written under .\ecl\2005a\Office\templates. However whenever simulation results are compared between two or more cases, as seen in this exercise, another
.GRF file is used, one that by default only displays the Field Gas Production Rates and the Field Average Pressure.
One may select the COALBEDMETHANE.GRF file to compare more plots than the two mentioned above.
1. Highlight the Desor-Time CBM case in ECLIPSE Office.
2. Select Case | Compare…
3. Select LANG1 as the case to compare results of Desor-Time to.
4. In the field next to Compare GRF, change the path to the complete path name where the
COALBEDMETHANE.GRF file was saved:
D:\ecl\2004a\Office\templates\COALBEDMETHANE.GRF for example if ECLIPSE was
installed under D:\.
5. Click on Plot. You should now see a complete set of line plots compared.
Changing ECLIPSE Office Settings
By default ECLIPSE Office is not configured to call the COALBEDMETHANE.GRF file in the Case | Compare… dialog. It is possible to change these settings.
1. Save your project and close ECLIPSE Office.
2. Open the CONFIG.ECL file located in the macros directory under the ECLIPSE installation folder
(ecl by default).
3. Make a search (Ctrl + F) on the word compare.
4. Under SUBSECT CASECOMPARE, change the string
$ECLARCH/$ECLVER/office/grf/compare.grf to
$ECLARCH/$ECLVER/office/templates/COALBEDMETHANE.GRF.
5. Save the changes.
6. Fire up ECLIPSE Office, Open the project previously saved and highlight the case Desor-Time.
7. Select Case | Compare…
8. Notice how the Compare GRF field now automatically points to the correct GRF file.
Creating a New Project
7. In your Windows Explorer, under the CBM folder created in the previous exercise, create a new
folder named Exercise3.
8. From the ECLIPSE Simulation Software Launcher, start Office and select Exercise3 as the startup
directory.
9. As described in Exercise1, create a new project by selecting File | New Project…Name it SENS
and click Open.
10. From this new project, create a template case named Base.
11. Rebuild the model created in Exercise2. Alternatively, the settings from Exercise2 Gas-Water
model may be imported. In order to achieve that, in the CBM Template module, select File | Open … and select the template start up file Gas-Water.TPM saved in the Exercise2 folder. Click Open.
12. Browse the various panels to inspect the value of the various parameters imported.
13. Run ECLIPSE.
14. Close the CBM Template module. In ECLIPSE Office, save the project.
We will now create a series of models from this base case. In each case, parameters used to characterize the reservoir rock, the reservoir initial conditions as well as correlations used to derive relative permeabilities to different phases and PVT tables will be varied to investigate the impact of such changes on the simulated reservoir response.
Sensitivity to Initial Conditions
Gas-Water Contact Depth
1. In ECLIPSE Office, from the Base case, add a clone CBM case named GWC1.
2. In the Reservoir Description panel, select the Initial Condtions.
3. Change the Gas-Water Contact Depth from 1020 ft to 1010 ft. Click Apply.
4. Generate the model.
5. Run ECLIPSE.
6. Close the CBM Template module.
7. Repeat the previous steps to clone Base into case GWC2 and set the GWC above the top of the
reservoir (say 900 ft) so that the cleat system is initially filled with water.
8. Run ECLIPSE.
9. In ECLIPSE Office, select Case | Compare…
10. Ctrl-click to select Base and GWC1 to compare the results of GWC2 to.
Observe the effect of varying the gas-water contact on the early gas production rate. As the gas-water contact is set to shallower depths, there is initially less gas in the fracture space and therefore less gas produced early on.。