Field Application of Converted De-Sander Unit as a High-Pressure Gas Liquid Compact Cyclonic Separator for Gas Lift/Gas Injection Supply Through Innovative Reverse Engineering and Retrofitting Design

Abstract Liquid and solid removal from multiphase flow stream is very vital for upstream oil and gas industry for its various applications. Many conventional techniques have been developed and optimized with many stages of separations for its various usage such as fuel gas, lift gas, sale gas etc. However, the demand for smaller & compact equipment increases especially in an offshore platform brownfield environment. Reverse engineering and retrofitting with an innovative design is an easy way out. In this study, a High Pressure 5K rated De-sander is converted to High Pressure Gas Liquid Compact Cyclone Separator (GLCC) to separate High Pressure gas from liquid for gas injection and Gas Lift purposes. All Cyclones are based on the same working principle and the main difference in the design based on the specific separation requirement. The centrifugal acceleration exceeds the gravitational acceleration by far, enabling a similar degree of separation, but in a significantly shorter time and smaller volume. Considering the original equipment design conditions and keeping within the limit, the new field requirements have been taken into evaluation. The same mechanical body of de-sander equipment can be used for different type of applications with different designs of internal cyclones/inserts. Also, the inlet and outlet piping, instrumentation control system have been redesigned with different control strategy. Required field modifications have been carried out. New insert design made based on required new multiphase flow rates, pressure, temperature and fluid properties. Inlet and outlet piping designs were modified to suit new design conditions. Field tests carried out to evaluate performance with actual field set up. Inlet tangential flow properly designed. Liquid separation efficiencies determined for various multiphase flow rate at different pressure and temperature conditions depending on the High-pressure donor wells. Liquid hold up under Zero-Net Liquid Flow at various flow conditions assessed. Acceleration field is increasing with increasing throughput and increasing pressure drop across the cyclone. Whilst the residence time decreases with increasing flow the increase in acceleration field is more significant. Separation efficiency increase with increased flow rate. Smaller cyclone provides higher efficiency. If the gas well start produces more liquid then apparently the bulk phase density will increase and the separation efficiency will decrease. Both liquid and solid particles could be simultaneously removed with close operational settings. Good level of dryness up to 90 % could be achieved. Reverse engineering and retrofitting of Cyclonic equipment such as de-sanders provide huge opportunity in the oil & gas industry. The design offers a large operating range with good performance and provide a quick, cost effective and compact solution for various applications.