The OLGA dynamic multiphase flow simulator models transient flow (time-dependent behaviors) to maximize production potential. Transient modeling is an essential component for feasibility studies and field development design. Dynamic simulation is essential in deep water and is used extensively in both off- and onshore developments to investigate transient behavior in pipelines and wellbores.
Transient simulation with the OLGA simulator provides an added dimension to steady-state analysis by predicting system dynamics, such as time-varying changes in flow rates, fluid compositions, temperature, solids deposition, and operational changes.
From wellbore dynamics for any well completion to pipeline systems with various types of process equipment, the OLGA simulator provides an accurate prediction of key operational conditions involving transient flow.
Pressure/enthalpy formulation in OLGA Compositional Tracking
OLGA 2017.1 extends the capabilities of OLGA Compositional Tracking and incorporates a pressure/enthalpy formulation. The pressure/enthalpy formulation comes as an option to the pressure/temperature formulation and significantly improves the ability to address systems with rapid transitions between single-phase and multiphase conditions. The functionality enables robust thermodynamic modeling when the operating profile crosses the phase envelope for CO2 with impurities, geothermal wells, LNG, etc.
Cubic-Plus-Association (CPA) equation of state in OLGA Compositional Tracking
The Cubic-Plus-Association (CPA) equation of state (EOS) is an extension of the Redlich-Kwong-Soave (RKS) cubic EOS that incorporates the effect of chemical association. The effect of chemical association (hydrogen bonding) is important when polar components such as water and inhibitors are present, and CPA improves the description of such fluid compositions. CPA is the default EOS in Multiflash.
Revised input structure for inflow performance relationships
The input for inflow performance relationships (IPRs) has been revised to improve user experience and enable incorporation of new IPRs. The input for lumped inflow through the WELL keyword and distributed inflow through the ZONE keyword has been replaced by the consolidated keyword RESERVOIRCONTACT. RESERVOIRCONTACT contains information about the inflow location and the reservoir properties. The functional dependency given by the IPR has been extracted into dedicated keywords, one per IPR, on the Library level.
Horizontal inflow performance relationships
OLGA 2017.1 incorporates two new horizontal IPR models: Joshi and Babu-Odeh.
Enhanced stability for no-flow conditions (shut-in)
The numerics in the OLGA simulator is designed for flowing conditions. This may cause instabilities when approaching no-flow, for example, during shut-in. Three specific improvements target stability when approaching no-flow.
The first improvement targets the Courant-Friedrich-Levy criterion applied in the OLGA simulator. This considers the fluid velocities, and as the simulation approaches no-flow conditions, the timestep increases until it is bounded by the maximum timestep. By incorporating the velocity of interfacial waves, the timestep is restricted when approaching no-flow, which in turn improves the numeric stability.
The second improvement targets the modifications imposed by the SHUTIN keyword. Previously, SHUTIN considered the stability only at the gas/liquid interface, effectively making it a two-phase consideration. Now, this is extended to consider both the gas/oil and oil/water interfaces, improving the treatment of three-phase and two-phase liquid/liquid systems.
The third improvement is an option to automatically activate and deactivate SHUTIN. Previously, the user had to define where and when the SHUTIN functionality should apply. OLGA 2017.1 possesses the ability to automatically determine this based on the local Froude number.
Well-centric plotting in the OLGA Well Editor
The OLGA Well Editor is extended with an additional tab Plot that enables plotting against the measured depth on the y-axis. With the OLGA Well Editor’s knowledge about the topology of the annulus, tubing, and wellbore, the built-in plotting can consistently visualize results for the various parts in the same plot.
Valve opening through diameter and bean size
OLGA 2017.1 introduces the ability to specify valve opening through the absolute diameter of the opening. Furthermore, it is possible to give the diameter in bean size (64ths of an inch).
Updated library of electric submersible pumps
OLGA 2017.1 comes with an updated library with more than 400 different electric submersible pumps.