TULSA, OK— A new Department of Energy-funded technology to upgrade low-quality natural gas—a resource that accounts for almost one-third of America's known gas reserves—has been successfully commercialized and is now a multimillion-dollar business.
A large portion of the nation's natural gas production stream comes out of the ground contaminated by water, carbon dioxide, hydrogen sulfide, or nitrogen and other inert gases. These contaminants must be removed from the production stream in order to provide pipeline-quality natural gas for delivery to consumers. This low-quality natural gas resource has been estimated at more than 60 trillion cubic feet (Tcf) of the Nation's total proved gas reserves of more than 192 Tcf.
In this case, the DOE-backed technology targets cleanup of natural gas with a high nitrogen content. The standard U.S. natural gas pipeline specification for nitrogen content is less than 4 percent. On this basis, about 17 percent of known U.S. gas reserves, or more than 32 Tcf, falls short of pipeline-quality levels specifically due to high nitrogen content. That makes nitrogen the largest target for cleanup in the low-quality natural gas resource base.
Some of this high nitrogen content gas can be upgraded to pipeline specs through dilution with low nitrogen content gas, if available, or through treating and conditioning at commercial cryogenic processing plants. High nitrogen content gas is processed at large (50-1,000 million cubic feet per day capacity) cryogenic plants to take advantage of economies of scale.
A large part of the nation's high nitrogen content gas lies in many modest-size deposits?mainly operated by small, independent operators—that are too small to be economically processed with cryogenic technology. Consequently, about 1 Tcf of this discovered resource remains economically unproducible. That volume is equal to almost 5 percent of U.S. annual consumption of natural gas.
If America 's significant resource of subquality natural gas is to be fully developed, advances in alternative nitrogen separation technologies are needed. One such technology is membrane separation, which entails using liquid or solid barriers to separate and selectively transport components of a fluid stream. It is generally a passive and energy-efficient process. Membrane separation technology is gaining greater attention these days in natural gas production and processing, especially in small, portable units mounted on skids or packaged into field production facilities.
Membrane separation can be costly in some applications, although it often is the only feasible method for cleaning up some natural gas streams. Industry is pushing the envelope on cutting costs and improving efficiencies in membrane technology in order to make this the preferred option for a broader array of marginally economic subquality gas deposits.
The Energy Department funded a 5-year research project by Membrane Technology and Research Inc. (MTR) to develop and demonstrate a membrane separation process to separate nitrogen from natural gas with a high nitrogen content. The project marked the first demonstration of a new membrane technology to treat a very low volume (1 million cubic feet per day) of otherwise unusable high nitrogen content natural gas. MTR's process divides the natural gas into two streams: a pipeline-quality product gas and a high nitrogen content gas stream that is burned as fuel for the MTR unit's compressor.
After assessing the technology's successful performance in test wells in an Ohio gas field pilot, MTR plans to demonstrate the technology further with a final test at facilities operated by a small independent company, North Texas Exploration, in a Texas/Oklahoma natural gas field. MTR also is negotiating with a large utility, Dallas-based Atmos Energy, regarding participation in that final demonstration test.
The DOE-funded MTR technology already has drawn the attention of one the world's biggest multinational engineering and construction firms, ABB Lummus Global. MTR signed a marketing and sales partnership with the giant firm to help market the technology. Since then, the partnership has sold six commercial nitrogen rejection natural gas membrane separation units based on the technology. Commercial sales to date total almost $2.6 million.
The National Energy Technology Laboratory manages the MTR research project, which is expected to conclude this year.