Production of natural gas and liquefied petroleum gas from flare gas using methanol based process

Abstract

Flare gas utilization has been a topic of discussion among stakeholders of the Nigerian Petroleum Industry and one of the simplest technical and commercial strategies is to send these gases to an existing gas pipeline with spare capacity. Peculiarities of flare gas can pose different challenges but the feasibility of the project depends on exogenous factors such as proximity to gas pipeline and availability of markets. In this work, an energy integrated methanol-based gas processing method for treatment and recovery of Liquefied Petroleum Gas (LPG) is presented using a high flaring intensity Nigerian Marginal oilfield close to an existing gas pipeline. A capacity of 60 MMscfd was determined using the flaring profile of the oilfield and a propane refrigeration system was selected as the cold process. ASPEN HYSYS V9 Cubic Plus Association (CPA) equation of state was used to optimally predict methanol (used as a hydrate inhibitor) partitioning in the methanol-hydrocarbon system. This process produced 57.15 MMscfd of natural gas, 163.7 tonne/day of LPG, and 33.19 tonne/day of stabilized condensate in line with Nigerian gas transport code specifications. The equipment count in comparison to other gas processing schemes, operational flexibility, and ease of scalability indicates that it is an economic technology that will be well suited for solving the gas flare scenario in the Niger Delta region by converting these wasted gas into more useful products.