Multi-Tank Model
MBAL can be model a single tank reservoir system as well as multiple tanks reservoirs, i.e. reservoir which have distinct tanks that are in communication, with one tanks providing energy (pressure support) to other tanks. These can in direct communications between reservoir tanks and/or through a common aquifer.
PVT: MBAL can handle multiple tank reservoir models with:
- a different PVT per tank; and/or,
- Variable PVT: Different variable PVT inputs (PVT variation with depth) can be set for each tank.
Sources of Energy
In developing and understanding the energy sources of a reservoir it is always recommended to start with a single tank model. Mutli-tanks can be inferred by looking at the Campbell plot for the single tank system - where the plot shows the energy in the reservoir is flat line initially and in later time there is an increasing trend in the data - i.e. an additional energy source. This signifies that initially the reservoir does not see any energy from outside sources, however, at some point there is energy coming from somewhere. This energy cannot be an aquifer (since it would show from day one) and we can conclude that a fault has been broken and a second reservoir is supporting the first.
Transmissibility Parameters: are used to establish the different communication links between the tanks in a multi-tank MBAL model.
Crossflow Injectivity Index: where there are multi-layers communcating through the wells these can be modeled for the producer wells. Normally if a layer of a production well starts to act as an injector (due to crossflow), the IPR function is simply extrapolated for negative rates. Different IPR's can be defined for negative rates. This can then be used to reduce the injectivity of a layer and thus give better stability to cross-flow.
