Condensate Stabilization Process - Development and Optimization Approach

Heavy hydrocarbons condensed from a gas during its extraction form a condensate enriched with a group of hydrocarbons C5+. This by-product of gas producing and gas-processing industries is an important commodity. The Brazilian Oil&Gas companies have recently discovered many gas and condensate reservoirs pushing the opportunity to have new process studies. The liquid that are separated from the gas stream in the first separator may be flowed directly to a tank or may be "stabilized" in some fashion. It may be shipped without further processing, but it is stabilized often by blending into the crude oil stream and thereby sold as crude oil. These liquids contain a large percentage of methane and ethane, which will flash to gas in the tank. This lowers the partial pressure of all other components in the tank and increases their tendency to flash to vapors. The process of increasing the amount of intermediates (C3 to C5) and heavy (C6+) components is called Condensate Stabilization. This process is performed primarily in order to reduce the vapor pressure of the condensate liquid to atmospheric storage tanks. Condensate may contain a relatively high percentage of intermediate components and can be easily separated from entrained water due to its lower viscosity and greater density difference from the water. Regularly specifying three-phase separator when necessary solves the water separation problem. In general, condensate stabilization accomplishes several goals, the foremost of which are: to increase the recovery of methane-ethane and LPG products; to lower the vapor pressure of the condensate, therefore making it more suitable for blending and reducing the evaporation losses while the product is in storage or shipment; to sweeten the raw liquids entering the plant by removing the hydrogen sulphide and carbon dioxide contents, in order to meet the required specifications; to maintain the purity and molecular weight of the lean absorption oil, free of certain components like pentanes and heavier hydrocarbons, absorption process is applicable. The stabilization of condensate streams can be accomplished through either flash vaporization or fractionation. A typical three stage flash separation system is comprised by a high pressure, medium pressure and low pressure separation The gas outgoing the vessels can be recompressed or used as fuel gas depending on the returned value in terms of product production from that gas. The stabilized condensate has to meet the specifications and is led to atmospheric storage. In almost all cases the molecules have a higher value as liquid than as gas. Crude oil streams typically contain a low percentage of intermediate components. Thus, it is not normally economically attractive to consider other alternatives to multistage separation to stabilize the crude. In addition, the requirement to treat the oil at high temperature is more important than stabilizing the liquid and may require the flashing of both intermediate and heavy components to the gas stream. The fractionation is a complex and precise process taking granted the product specification. It consists in a process where a higher operation pressure than atmospheric is possible due to the temperature profile in the stabilization column, where the light compound are forced to flow up and the heavy cross down the column. The presence of only the reboiler facilitates the control of the condensate product keep-set The recovered gas is then rich in lighter compounds, CO2 and water. The destination can be the recompression and mix with the main gas stream to pass through the dehydration, acid gas removal and fractioning. The selection of the separator stages pressures and the number of stages are variables to develop and define in a conceptual phase project, comparing to the condensate stabilization column in terms of energy supply and overall results. This paper aim to study the behavior and select the best process variable set for two different typical gas/condensate fluid production well. The issue is to optimize and reduce the total power consumption and illustrate the great differences between each system.