Multilayer Allocation Editor

With the Multilayer Allocation Editor (located within the Editors pane), you can assign flow proportions for each layer in a multilayered well. Using these flow proportions, rates for each layer can be calculated from the overall well rates in the Production Editor. Entering values in this editor must be done at the well level.

User Interface

A blank Multilayer Allocation Editor for a well with two layers looks like this:

Since flow proportions are allocated on a time basis, the first step is to specify at least one calendar date. If only one date exists, then the flow proportions will apply to every date in the Production Editor. However, if the proportions are changing over time, then multiple dates can be entered into the allocation editor.

Interpolation

Interpolation is required when the date range in the Multilayer Allocation Editor does not exactly match the Production Editor. In such cases, there are two interpolation options: linear and step.

1. Linear interpolation calculates an average change in flow proportions from one date to the next. This is the default setting.

2. Step interpolation keeps the proportions static until the next date is reached. When that next date is reached, the proportions instantly change.

Regardless of the specified interpolation method, any entries in the Production Editor that occur before the first date in the Multilayer Allocation Editor will have their allocations “step interpolated” backwards. Likewise, any production data after the last-specified allocation date will continue to use that allocation.

Specifying Proportions – Overall

The simplest way to divide the rates is to specify the overall flow proportions. This method applies the same allocation to all fluids equally. The only thing that can be set is the percentage of the total fluid that comes from each layer. Percentages are set indirectly by entering values into the flow proportion fields. For example, in a two-layer well, if each layer was specified with a proportion of “1”, then 50% of the total fluid would be allocated to each layer.

Specifying Proportions – Per Fluid

By specifying proportions on a per-fluid basis, you can have much finer control over allocations. For example, if you were producing only gas from one layer, and only water from another layer, then a per-fluid allocation is necessary.

Select Per Fluid from the toolbar and the fluid proportion fields will become editable (and any overall proportions will be ignored). If “Auto Template” is enabled in the Editors pane, the appropriate fluid columns in the Multilayer Allocation Editor will automatically be created. For further information on how templates work, see Template Tasks.

Special Considerations

There are special considerations for condensate and time on production / injection.

Condensate

Whenever pressure calculations are performed with condensate recombined into the gas, extra attention should be paid to the Multilayer Allocation Editor. Since both gas and condensate rates can be allocated differently, the condensate-gas ratio can be quite different from one layer to the next.

In the Production Editor for the well, there are two ways to control the CGR Source. When “CGR” is selected, it uses the allocated condensate volume and gas volume to calculate a CGR for each row. However, if “CGR_custom” is selected, then the per layer CGR_custom is calculated as follows:

Time on Production / Injection

Whenever a layer has none of the proportions allocated to it for a given row, it will have zero allocation of the time on production (or injection). Otherwise, 100% of the time on production (or injection) will be allocated.