Low Quality Natural Gas(LQNG) is the gas from any reservoir that contains enough non-hydrocarbon gases to lower the fuel value or other qualities of the produced gas below commercial pipeline standards. Much of this natural gas cannot be produced economically because it contains significant quantities of contaminants. The most common contaminants are water, carbon dioxide, hydrogen sulfide, nitrogen, and heavier hydrocarbons. Other contaminants that occur less frequently and in small concentrations are helium, argon, hydrogen, and oxygen. LQNG is an extensive, but largely underdeveloped, energy resource. If this latent energy resource is to be exploited, markets for non hydrocarbon components must be promoted and expanded, and more effective methods for upgrading LQNG must be developed.

The main gas separation methods in use today are liquefaction/distillation, absorption, adsorption, and membrane-based processes. Membrane separation technologies are rapidly emerging as the preferred separation technology, particularly portable skid-mounted and packaged field processing units. Though, current membrane processes may be costly in some applications, they may be the only method for practical use in natural gas cleanup.

Important issues including process design and reliability issues that need to be resolved for LQNG separation technologies are: (1) cost of the fuel needed to drive the separation and the need to increase the energy efficiency of the process and (2) the high unit cost of gas conditioning if processed at low flow rates. Consequently, there is a need to develop new separation concepts that can yield significant efficiency improvements and cost reductions. Novel membrane applications, the study of adsorption fundamentals, and the thermodynamics and chemistry of natural gas mixtures are viable research areas.

LQNG upgrading research activities include: (1) research on novel passive and facilitated-transport polymeric membrane concepts seeking to increase selectivity, permeability, and long-term stability at practical operating conditions; (2) research targeted at developing novel adsorbents and absorbents and evaluating them in a pressure or temperature swing mode; (3) research to identify advanced and potentially economic novel hybrid and LQNG separation technologies, assess their feasibility, and develop field applications of promising processes; (4) conducting process and economic evaluations of membranes, adsorbents, absorbents, and other hybrid technologies as they apply to upgrading LQNG to pipeline specifications and (5) field tests of new economic processes.

LQNG research has integrated the resources of DOE, GRI, and private industry to develop LQNG upgrading technologies economic at a single well scale of operation. The strategy for LQNG research is to continue to advance the development of polymeric membrane materials, to identify existing novel or advanced gas separation technologies, and to determine the technical and economic feasibility of LQNG upgrading technologies. If technical and economic feasibility can be demonstrated, the next step for promising gas separation concepts is continued development through an applied program in the field.

NETL has been involved in selecting high visibility natural gas upgrading basic research and field demonstration projects as part of an active gas processing program. This program is no longer active but NETL is involved in the completion of some field demonstrations from the past program.