Recovery of natural gas liquids with membranes from associated gas on Newfoundland and Labrador offshore production facilities

Beronich, Erika (2006) Recovery of natural gas liquids with membranes from associated gas on Newfoundland and Labrador offshore production facilities. Masters thesis, Memorial University of Newfoundland.

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Abstract

The market for natural gas has been rapidly increasing and is becoming one of the most important sources of energy in the world. Natural gas is a "cleaner" burning fuel when compared to other fossil fuels and therefore environmental impacts are minimized. Gas produced (associated gas) with oil is largely methane with heavier fractions referred to as NGL (Natural Gas Liquids). NGL is used as feedstock for petrochemical processes or as fuel for industrial and domestic purposes. The recovery of NGL is commonly carried out at onshore oil and gas operations where space and weight are not critical design parameters. The limited space on offshore platforms makes NGL recovery a challenge. Currently, in the Newfoundland and Labrador Offshore, the associated gas is re-injected, used for power on the platforms, and some is flared but not recovered due to the difficulties to storage and transport in this remote location. This associated gas contains high levels of NGL, making attractive its recovery from the economical and environmental points of view. This thesis describes in detail the development of a membrane process to recover NGL. Different processes such as turbo-expander, absorption, adsorption, external refrigeration and membranes are reviewed and compared. As a result of this comparison, membranes are proposed as a feasible option for NGL recovery. Several membrane models are investigated. Membranes are placed in different locations in a three-stage separation train on an offshore platform, and the effect of pressure, inlet temperature process, flow pattern, and location in the process are analysed. The analyses are then extended by incorporating the recycle of the permeate and residue streams of the membranes to separators. Twelve alternative configurations of the original process are investigated with the objective of evaluating the impact of the membranes on the production of crude oil base. As a result, it is demonstrated that some of the configurations considered increase the production of crude oil.

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