Assessment of Diethylene Glycol (Deg) Dehydration System in a Natural Gas Processing System

Abstract

The natural gas found in Nigeria's Obagi field, specifically in OML 58 where the Obite gas processing plant is located, typically contains water vapour. It is generally assumed that about 98% of gas discoveries in this area are saturated with water. The presence of water in either liquid or vapour form creates technical challenges. This problem is prevented through dehydration to prevent hydrate formation. To achieve optimal production, cost-effectiveness, and improved marginal gains in gas processing, dehydration systems need to be carefully evaluated. This paper offers the use of a simulation tool to tackle the natural gas dehydration system at the Obite Gas Plant. Process conditions of 84bar and 35^oC and gas flow rate of 8MMSCFD, as the input data. Results indicate a DEG flow rate of 12.735m³/h, the water volume was reduced to 2.3915lb/MMSCF from an early value of 9.92lb/MMSCF. This is below the pipeline specification. The volume of methane recovered with a flow rate of 74%, for a DEG flow rate of 2.4m³/h, 4.6lb/MMSCF of water recovered in the gas stream. DEG dehydration can be used for dehydration systems due to its ability to meet low temperature and dew point specifications, and low initial and operating costs. After investigating various dehydration units at Obite gas processing facility, it is apparent that DEG can be used alongside TEG and many of the problems encountered and costs incurred could have been prevented with a better engineering understanding of the dehydration system.