Plant Wide Oil and Gas Separation Plant Optimisation using Response Surface Methodology

摘要

In this paper we will demonstrate Response Surface Methodology (RSM) applied to process simulation of an offshore oil and gas separation plant. By performing surrogate experiments according to Design of Experiment (DoE) and subsequent construction of multiple linear regression models for the chosen responses, the overall separation process is optimised in terms of power consumption under the constraints of quality specification of gas and oil export, respectively The fluid treated in the separation plant is rich in NGL (Natural Gas Liquids) which causes challenges in meeting the export specifications. Further, the NGL causes increased condensate recycle in the compression system thereby increasing power consumption for the compressors as well as increased cooling for heat exchangers. Offshore the NGL is difficult to dispose, which makes fractionation unattractive and the NGL must be exported via the oil (partly stabilised) or via the gas (rich gas) or a combination of the two. Effectively, this violates the export specifications and the NGL must be extracted in on-shore facilities either at the oil or gas receiving facilities. By exploring different options, applying RSM, it is found that in terms of overall power consumption export of NGL with the gaseous products is more effective that exporting the NGL with the partly stabilised oil. The methodology used in the present paper can also be applied to existing production facilities as a generic optimisation tool. Due to the simplicity of the regression models mimicking the separation plant they can be coupled with the overall process control for potential on-line plant optimisation.