A New Tool for Performance Monitoring of Pseudo Dry Gas Technology Validated with Experimental Data

Remote deepwater gas field development poses challenges due to the long tieback and requirement for remote control and monitoring. Recently, a novel Pseudo Dry Gas (inline gas-liquid separator) technology has been developed and extensively tested in a 6" flow loop at low and high pressure, to tackle the long tieback issue. The technology offers significantly lower CAPEX and OPEX by removing liquid phases from the main gas line, hence, reducing the back pressure and flow assurance issue related to wax or hydrate formation. Given the harsh environment and inaccessibility of deepwater installations, a tool is required for remote monitoring (in real-time) and prediction of the performance of this novel Pseudo Dry Gas (PDG) system and to help the operator to optimize production. The paper aims to present the development of the solution. The tool is able to predict PDG performance efficiency, multiphase flow behavior, and associated FA issues in the flowline based on continuous input from field sensors. In this work, a transient numerical model of the PDG technology has been developed and combined with a transient multiphase flow simulator using a plug-in based architecture. The tool was validated with the extensive 6" flow loop data and tested under dynamic conditions covering ramp-up or turn-down, shutdown, normal operation, and operation beyond the design envelope. The flow loop test data covers low and high pressure, horizontal and near horizontal, and various fluids representing gas, water, condensate, oil, and oil-water mixture. In addition to that, a steady state case comparison with a commercial software was conducted for a deepwater field. The validation results show the ability of the tool to predict PDG performance (the separation and liquid level in the liquid chamber) under the dynamic condition with good accuracy. The dynamic test results showed that PDG technology effectively separates most of the liquid within its operating envelope producing a pseudo-dry gas. The liquid removal reduced pressure drop in the main gas line by half, minimizing slugging, and liquid surge to receiving facilities. The liquid level in the liquid chamber fluctuates depending on inlet liquid rates and maximum liquid extraction rate by the liquid pump. Beyond PDG operating envelope, the simulator was able to predict decreasing separation efficiency and chamber liquid level. The simulation results implied that the pressure drop reduction will be higher for longer pipelines which make the technology suitable for long subsea tiebacks.