Black Oil Delumping Techniques Based on Compositional Information from Depletion Processes
- Kassem Ghorayeb (Schlumberger) | Jonathan Anthony Holmes (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- October 2007
- Document Type
- Journal Paper
- 489 - 499
- 2007. Society of Petroleum Engineers
- 4.1.9 Tanks and storage systems, 5.5 Reservoir Simulation, 2 Well Completion, 5.2.1 Phase Behavior and PVT Measurements, 5.2 Reservoir Fluid Dynamics, 4.6 Natural Gas, 3 Production and Well Operations, 5.4.2 Gas Injection Methods, 6.5.2 Water use, produced water discharge and disposal
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Black-oil reservoir simulation still has wide application in the petroleum industry because it is far less demanding computationally than compositional simulation. But a principal limitation of black-oil reservoir simulation is that it does not provide the detailed compositional information necessary for surface process modeling.
Black-oil delumping overcomes this limitation by converting a black-oil wellstream into a compositional wellstream, enabling the composition and component molar rates of a production well in a black-oil reservoir simulation to be reconstituted.
We present a comprehensive black-oil delumping method based primarily on the compositional information generated in the depletion process that is used initially to provide data for the black-oil simulation in a typical workflow. Examples presented in this paper show the accuracy of this method in different depletion processes: natural depletion, water injection, and gas injection. The paper also presents a technique for accurately applying the black-oil delumping method to wells encountering crossflow.
With advances in computing speed, it is becoming more typical to use a fully compositional fluid description in hydrocarbon reservoir simulation. However, the faster computers become, the stronger the simulation engineer's tendency to build more challenging (and thus more CPU intensive) models. Compositional simulation in today's multi-million-cell models is still practically unfeasible.
Black-oil fluid representation is a proven technique that continues to find wide application in reservoir simulation. However, an important limitation of black-oil reservoir simulation is the lack of detailed compositional information necessary for surface process modeling. The black-oil delumping technique described in this paper provides the needed compositional information, yet adds negligible computational time to the simulation.
Delumping a black-oil wellstream consists of retrieving the detailed components' molar rates to convert the black-oil wellstream into a compositional wellstream. It reconstitutes the composition and component molar rates of the production stream.
Black-oil delumping can be achieved with differing degrees of accuracy by using options ranging from setting a constant oil and gas composition for the whole run to using the results of a depletion process: constant-volume depletion (CVD), constant-composition expansion (CCE), and differential liberation (DL).
The simplest method is to assign a fixed composition (component mole fraction) to stock-tank oil and gas. This could be applied over the whole reservoir, or, if the hydrocarbon mixture properties vary across the reservoir, different oil and gas compositions can be reassigned at any time during the run.
Some black-oil simulators have an API tracking feature that allows oils of different properties to mix within the reservoir. The pressure/volume/temperature (PVT) properties of the oil mixture are parameterized with the oil surface density. To provide a delumping option compatible with the API tracking, stock-tank oil and gas compositions may be tabulated against the density of oil at surface conditions.
|File Size||3 MB||Number of Pages||11|
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