Introduction
Tutorials
Improving a discharge simulation
A discharge simulation is the calculated conditions (such as pressure, enthalpy, fluid type) down a well discharging at a given steady-state mass flowrate read more.
This tutorial shows you how to run a discharge simulation for a well:
A discharge simulation can be TopDown or BottomUp read more. This describes a TopDown discharge simulation.
The tutorial uses the geometry configuration Actual geometry that you should have entered earlier.
This tutorial assumes you measured this data at the wellhead during the discharge test:
| Data | Value |
|---|---|
| Mass flowrate | 100 t/hr |
| Fluid type | Liquid |
| Wellhead pressure | 65 barg |
| Wellhead enthalpy | 1,500 kJ/kg |
| Wellhead CO2 | 4,000 ppm in total fluid |
| Wellhead NaCl | 0 ppm in total fluid |
In the sample database, open a new discharge simulation for 
.
Enter this data:
| Field | Enter |
|---|---|
| Description | TD 100 t/hr |
| Data | Enter | Note |
|---|---|---|
| Geometry Index | 1: Actual geometry | From the drop-down list, select a geometry configuration for MY WELL that you have entered earlier. |
| Feedzone Index | None | MY WELL does not have any secondary feedzones above the deepest, so it does not require a secondary feedzones dataset for this tutorial. If your well has secondary feedzones, then from the drop-down list, select the secondary feedzones for the the well you have entered earlier. |
| Formation Index | None | This tutorial does not require measured formation temperatures, so select None here. Usually the effect of specifying formation temperatures is slight. If you have a formation temperature profile for the well, select it from the drop-down list. |
| Test direction | TopDown | Select from the drop-down list read more |
| Flow correlation | WellSim | Select a flow correlation from the drop-down list; the default, WellSim , is usually best read more |
You must enter two of Pressure, Temperature, Enthalpy or Fluid dryness. When WellSim runs the discharge simulation, it calculates the other two fluid parameters.
For a TopDown simulation with two-phase flow at the wellhead, there are only two independent parameters. For instance, a given pressure and temperature determines the dryness 'X' (mass fraction of steam in total flow) and therefore the enthalpy 'Hl x (1-X) + Hv x X' where Hl = enthalpy of water at specified temperature and Hv = enthalpy of steam at that temperature. Usually specify pressure and enthalpy.
For a TopDown simulation with liquid reservoirs, the enthalpy at the wellhead is not much different from the enthalpy of the reservoir, which you can calculate from the temperature of the reservoir (for example, steam tables show that the enthalpy of a 250 C liquid reservoir is 1087 kJ/kg. Flow up a well is approximately iso-enthalpic; WellSim predicts an enthalpy loss of only about 25 kJ/kg up a typical well.
Things get tricky if the reservoir is two-phase or if there is a lot of gas (most commonly CO2) in the discharge.
For BottomUp simulations, starting from a single-phase liquid, dryness is automatically set to 0, and you enter two other parameters, usually pressure and enthalpy.
Usually specify pressure and enthalpy.
After you enter a fluid parameter, tick the box under the parameter.
For the two parameters you do not enter, untick the box under each parameter.
For this tutorial, enter:
| Field | Enter | Note |
|---|---|---|
| Mass flowrate | 100 | [t/hr] |
| Fluid type | Liquid | Select from drop-down list |
| Pressure | 65 | [barg] Tick the box under Pressure |
| Temperature | (empty) | No tick in box under Temperature |
| Enthalpy | 1500 | [kJ/kg] Tick the box under Enthalpy |
| Fluid Dryness | (empty) | No tick in box under Fluid dryness |
| Field | Enter | Note |
|---|---|---|
| Equation of state | Complex | Select from the drop-down list. The options are Simple and Complex. Complex is usually best, especially with significant concentrations of gas and or salts read more. |
| CO2 | 4000 | [ppm] (in total fluid) |
| NaCl | 0 | [ppm] (in total fluid) |
Measure all depths relative to the same point at the wellhead read more.
| Field | Enter | Note |
|---|---|---|
| Start depth | 0 | [m] Should always be zero. |
| Depth type | Measured | |
| Finish depth | 2500 | [m] |
| Depth type | Measured | |
| Depth increment | 25 | [m] |
The window should now look like this:
Click 
to preprocess the data. If WellSim finds errors, correct the numbers and click again.
During preprocessing, WellSim:
checks you have entered enough data
checks that the numbers you entered are consistent
estimates any fluid parameters that you did not enter (Pressure, Temperature, Enthalpy or Fluid dryness)
adjusts the fluid type and any numbers where WellSim considers them to be inconsistent with the fluid composition
displays any errors it finds
Click 
.
If you get the error Solution did not converge see here.
WellSim displays the calculated data down the well:
Note
WellSim has calculated values for Temperature and Fluid dryness at the wellhead.
Scroll up and down the text results (numbers). Look at the different Flow Regimes down the well. The flash point is at about 1580 m depth. Below this, the discharging fluid is liquid and above it is two-phase.
Even though you set the step increment to 25 m, the step increment can be different to this where there is a change (for example a the flash point, a feedzone or a change of wellbore diameter, of casing type, or of well angle). This is normal.
Click 
(top of window) to display the results as a graph:
If your graph does not look like this, change it.
Note
Temperature (red line): Above the flash point, the fluid expands rapidly as it converts from water to steam, which causes rapid cooling, which causes the knee in the temperature graph at the flash point.
Pressure (black line): The pressure change at the flash point is less dramatic as the fluid converts to steam progressively up the well, without a sudden change in density.
Change the graph to display Pressure gradient to see what causes the increase of pressure with depth at this mass flowrate:
This shows the friction and acceleration losses are small and the main cause of the pressure increase is gravitation, ie the weight of fluid in the wellbore:
As WellSim runs a discharge simulation, it writes a log file for the simulation, which can be useful if the simulation has a problem. To see the file after you have run a simulation, click the Simulation Log tab.
NOTE
The log file (called wssimlog.txt) is stored on your PC.
You can set what is written to the log in Preferences.
to save the discharge simulation and return to the discharge simulations window.Each discharge simulation uses a geometry configuration and might use a secondary feedzone feedzone configuration and a formation temperature configuration. If you change any of those configurations you will probably need to rerun the simulation to reflect the changes - the discharge simulation is said to be inconsistent.
To warn you about this, when you go to the discharge simulations window, WellSim checks if any of the discharge simulations use the configurations that have changed. If any have:
WellSim hilights in orange the any inconsistent simulations visible in the header window:
When you click an inconsistent simulation, WellSim hilights its data in the detail window:
When you edit an inconsistent simulation, WellSim hilights the text data.
When you go to the discharge simulations window, you have the option of displaying an inconsistency report:
To enable or disable this report for the current WellSim session:
Do not show the data inconsistency report during this WellSim session.WellSim gives these warnings for other kinds of data that become inconsistent, for example:
For a geometry configuration, if you change its well deviation or casing profile.
For an output simulation, if you change its discharge simulation(s).
Before you use a discharge simulation, try to improve it by changing it to better match a measured discharge profile at the same mass flowrate see here.