Pressure overview

On this form you find the pressure information for each compartment, where the fluids are in hydrostatic equilibrium. This form is directly linked to the information on the Fluid Levels form (i.e. Fluid Leg, GOC and FWL), and on the Fluid Properties form (i.e. formation volume factor, density). The pressure information is updated simultaneously if you make changes on the other two forms. All the depth level information displayed on this form is specified in TVDSS.

• Name  Name of the compartment, read-only.
• Zone  Name of the zone, read-only.
• Fluid Leg  Indicates the type of fluids present in a compartment, read-only.

• GOC  Gas oil contact for the fluid compartment, read-only.
• FWL  Free water level for the fluid compartment, read-only.
• Tilted FWL  If the 'Tilted' checkbox is checked in and a tilted FWL is assigned on the Fluid Levels form, displays the name of the tilted FWL surface for the fluid compartment, read-only.

• Reference Depth  The depth at which the reference pressure is calculated, editable. Either can be autofilled by clicking on the Autofill Reference Depth button () or can be entered manually.
• Calculated Well Pressure at Reference Depth  Once a reference depth value is entered, these pressure values are calculated automatically and are read-only. The calculations are based on the fluid pressure data assigned on the Assign Logs form. The fluid pressure data (i.e. the local measurements at specific points) are corrected to the reference depth. For this correction, the calculation uses the fluid densities entered on the Fluid Properties form.
  • Min  The minimum value among all the pressure values corrected to the reference depth.
  • Max  The maximum value among all the pressure values corrected to the reference depth.
  • Average  The arithmetic average of all the pressure values corrected to the reference depth.

See the image below showing how the well pressure data points are corrected to the reference depth. For pressure calculations in oil leg, oil densities specified on the Fluid Properties form are used. Similarly, for pressure calculations in water leg, water densities specified on the Fluid Properties form are used.






Image showing how the well pressure data points are being corrected to the reference depth. Min, Max, Average Calculated Well Pressure Data at Reference Depth (i.e. FWL in this case).    click to enlarge

• Reference Pressure  The pressure at the reference depth, editable. Either can be autofilled by clicking on the Autofill Reference Pressure button () or can be entered manually.

• Well Pressure Data Points  The number of pressure measurements (i.e. the local measurements at specific points, assigned on the Assign Logs form). The total number of data points as well as the number of data points measured in gas, oil and water leg can be reviewed.

To set the reference pressure per compartment

1. Select the fluid model of interest.
2. Click the Autofill Reference Depth button () at the bottom-left corner of the form or enter a reference depth value manually.
3. If you have provided the pressure log data, click the Autofill Reference Pressure button () at the bottom-left corner of the form or enter the reference pressure value manually.
4. Click OK to set the pressure value at the reference depth and close the form, or click Apply to set the values and keep the form open.

The fluid model is now fully populated with information and can be used for Volumetrics Study. To prepare for this, use the Fluid Model Grid Properties option under the model > Fluids > Output Tools to make the fluid grid properties available in the Volumetrics Study workflow.

How 'Autofill Reference Depth' works

The Autofill Reference Depth button () populates the table with a recommended reference depth value per compartment. The autofilled reference depth per fluid compartment is filled based on the information entered on the Fluid Levels form. The following priority sequence is followed:

GOC	FWL	Reference Depth
✔	None	GOC
✔	✔	GOC
None	✔	FWL
None	None	Average of TOP and BASE

• If a GOC is specified on the Fluid Levels form, the reference depth is set to the GOC.
• If a GOC is not specified and a FWL is specified on the Fluid Levels form, the reference depth is set to the FWL.
In case of a tilted surface as FWL, the reference depth will be set to the shallowest depth of the tilted FWL intersecting with the vertically projected boundary of the compartment.






Image showing how the autofill reference depth is projected with a tilted free water level surface. The shallowest intersection point (point C) of the tilted FWL with the compartment boundary project vertically on the compartment boundary to estimate the reference depth.    click to enlarge

• If neither GOC nor FWL are specified on the Fluid Levels form, the reference depth is set to the average of the shallowest and the deepest depth of a compartment, which are respectively specified as TOP and BASE on the Fluid Levels form.

How 'Autofill Reference Pressure' works

The Autofill Reference Pressure button () populates the table with a reference pressure value per compartment. It uses the fluid pressure data, i.e. the local measurements at specific points, which are assigned on the Assign Logs form. The autofilled reference pressure is the average of all the well pressure values corrected to the reference depth, i.e. Average Calculated Well Pressure at Reference Depth. See Calculated Well Pressure at Reference Depth for more on this. The wells that are taken into consideration are the assigned wellbores which intersect the compartment.