6.1
Batch configuration
The Batch simulation mode gives the user an opportunity to run one or several simulations without any interaction from the user. The operational conditions are defined prior to simulation start and the well control procedures are performed automatically. Several operational scenarios can be predefined. On the Run
configuration navigator bar there is an icon for Batch configuration, as shown in
Figure 6-1. Each simulation has its own set of operational data, and more simulation scenarios are added by using the Add button at the bottom of the window. A
simulation scenario can be deleted by using the Delete button.
A set of batch simulations are stored as part of the case file when using the File
Save option from the menu bar. All the simulations defined in one batch are based
on the same input file.
Figure 6-1 Set of batch simulations
Pre-kick circulation period defines the circulation rate before a kick is taken. Up to
two circulation periods can be defined, with different pump rates and duration. After the pre-kick circulation periods, the kick is taken at the circulation rate specified in the Interactive simulation control panel. If no pump rate is specified in the Interactive
simulation control panel the kick is taken without circulation.
The Kick intensity defines the degree of underbalance and thereby also defines the rate in which the kick is taken; see Figure 6-2 below. The corresponding formation
Drillbench Kick User Guide Page 41
pressure is determined by the specified kick intensity and the reservoir pressure defined in the Reservoir input parameter window is not used.
Figure 6-2 Definition of kick intensity
The pit alarm level indicates when the kick is detected at surface. When the alarm is triggered, the simulator will start the shut in procedure. The shut in procedure is performed according to the operational times given in the Surface equipment group in the Input Parameter section.
It is possible to perform a flow check after the pumps are stopped. The flow check may continue a certain time, or until a certain volume increase in the pit is achieved. The selection is made from the drop down list.
After the well is shut in, the wellbore pressure can be allowed to stabilize. The shut in time is either set by the user, or the well can be kept shut in until the bottomhole pressure equals the pore pressure and the influx has stopped. This is selected from the Shut in period drop down list.
Circulation rate is defining the pump rate when circulating the kick.
The circulation of the kick can be performed in three different modes; Drillers
method, Wait and weight and Reference depth.
6.1.1
Drillers method
The bottomhole pressure during circulation of the kick is controlled according to the shutin pressure plus a pressure margin to pore pressure defined by the user in
Dynamic safety margin and the kick circulation rate. After the kick is circulated out, a
kill mud is circulated at a given Kill mud circulation rate. The kill mud weight is calculated based on the Static safety margin.
6.1.2
Wait and weight
Circulation is performed according to a kill sheet computed by the simulator, with pre-determined pump pressure versus time. The static safety margin is taken into account in the computation of the kill mud weight.
Time
Pr
essure gradient
Hydrostatic head Formation pressure
Flowing bottomhole pressure
kick intensity underbalance
6.1.2.1 Reference depth
In this mode, the choke pressure while circulating the kick is controlled in order to keep the pressure at a certain well position constant. The depth and the
corresponding pressure at this depth is specified by the user.
Clicking the Calculate preview button will calculate and show the corresponding reservoir pressure for the entered kick intensity, and the corresponding ECD for the entered circulation rate. After the button is pressed, these values will update live when changing the kick intensity or circulation rate. The preview is dependent on the selected mud. Changing the mud type or mud density will require clicking the
Calculate preview again.
6.2
Sensitivity configuration
The Sensitivity simulation mode is a tool for running a number of sensitivity
simulations. The well control procedure is defined up front and the sensitivities are run automatically without any user interaction. Combining different sensitivity parameters the user can simulate many different sensitivity scenarios, e.g.:
Maximum kick size vs. kick intensity
Casing shoe position vs. kick intensity
Degasser capacity vs. kick intensity
This input page enables configuration of the initial parameters, detection and well control procedures as well as the two sensitivity parameters. See Figure 6-3.
Figure 6-3 Sensitivity configuration
Drillbench Kick User Guide Page 43
1. Rate
Circulation rate
2. Reservoir (equivalent, based on mud type, density and pump rate)
Kick intensity
Reservoir pressure 3. Kick detection (similar)
Kick Size (after pump off, reservoir)
Pit alarm level (after or when pump off, at surface)
The input expects that the two parameters are of different parameter groups and will not pass validation if they belong to the same group. The selected parameters will disable the input which is already covered by the parameters and enable the
missing input fields belonging to the parameter group not covered by the parameter selections. Flow check, initial without reservoir and circulation mode without
circulation rate are always mandatory input.
Clicking the Calculate preview button will calculate and show the corresponding reservoir pressure for the entered kick intensity (or vice versa), and the
corresponding ECD for the entered circulation rate. After the button is pressed, these values will update live when changing the kick intensity, reservoir pressure or circulation rate. The preview is dependent on the selected mud. Changing the mud type or mud density will require clicking the Calculate preview again.