Schlumberger OLGA 2017.2 Oil and gas software company SPT Group, has released the latest version of its market leading multiphase flow simulator OLGA 2017.2, is a computer programme to simulate the simultaneous transport of oil, gas and water through the same pipeline. Field developments with such multiphase transport are much more economic than developments with traditional offshore separation of gas, oil and water and single-phase transportation OLGA 2017.2 - RELEASE NOTES: These notes accompany the release of OLGA 2017.2 from Schlumberger. The notes describe changes in OLGA 2017.2 relative to OLGA 2017.1. Fixed issues and minor enhancements in OLGA 2017.2 Fluids - Improvement in PH formulation in Compositional Tracking When using the PH formulation in Compositional Tracking, and especially in low flow rate situations, the heat transfer from or to the fluid could result in phase mass transfer in the single-phase regions. This has been resolved. (VSTS-1039285) - Wrong water cut exported by Multiflash to fluid properties table When a fluid properties table (.tab) is generated from Multiflash 6.2.37, the water cut (WC) at standard conditions is incorrect. This causes erroneous mass flow rates of water if the inflow is defined using standard conditions. The output variables at standard conditions for water are also affected, and in turn the transmitters using them. This has been resolved in Multiflash 6.2.37b which is part of OLGA 2017.2 Leak/Valve - Improvement for choke equilibrium model For very low pressures, when the choke equilibrium model was set to EQUILIBRIUM, the derivative of mixture density to pressure was not consistent with the density change with pressure. This inconsistency could lead to a non-convergence problem when calculating the critical flow, resulting in gross underprediction of flow through the valve. This has been resolved. (VSTS-1056352) - Fix in temperature dependent correction of dome pressure for gas lift valve (GLV) The temperature used to calculate the dome pressure of a GLV was set too high. Because the temperature was set too high, the casing and tubing pressures that were calculated were incorrect. This caused that the GLV valve would not open at the correct pressure. This has been resolved. (VSTS-1056647) Wax Deposition/Pig - Effect of pig leakage flow on wax plug friction length In OLGA 2017.1 and earlier versions, the leakage flow through a pig was not accounted for when estimating the friction length of a downstream wax plug. Depending on the leakage flow rate, the pressure induced bypass flow through a pig could either prevent build-up of the wax plug or, at least, reduce the growth rate. A simple model to approximate this effect has been implemented. An increase in leakage rate now results in a reduction in the friction length of an existing wax plug. With a sufficiently large leakage rate, the bypass flow is assumed to flush away the wax stripped by the pig, preventing any wax plug build-up. This is reflected by reporting small values, or zero, for the output variables PIGWXPLEN and PIGWXPFF. (VSTS-1024561) - Crash when pig used for wax removal passed internal node In OLGA 2017.1 and earlier versions, if there were no wax components upstream of a pig, for example, when the pig was pushed by water, the simulation would stop with an internal error when the pig entered an internal node. This has been resolved. (VSTS-1024605) - Corrected wax deposition for negative flow Previously, for flow in the opposite direction of the flow path direction, the wax deposition was typically smaller than for an identical flow in the positive direction. The wax deposition on the wall is now independent on the flow direction. (VSTS-986646)