Offshore Dehydration of Natural Gas
Publication Date: 2009-May-05
The IP.com Prior Art Database
The M. W. Kellogg Company Engineers of Quality
TO: A. E. Cover DATE: 17 January 1994
FROM: R. L. McKee
SUBJECT: Submittal of Paper to Publication Committee
Paper Entitled, "Offshore Dehydration of Natural Gas: An Evaluation of Alternatives"
Attached for department manager approval is the subject paper planned for presentation at the 1994 Offshore Technology Conference in Houston 02-05 May 1994. Verbal permission for publication has been received from Gas Research Institute. Written authorization has been requested and should be received soon.
Please forward this paper on to Mr. U. R. Miller, Publication Committee Chairman, for Publication Committee review and approval.
xc: C. A. Durr
T. H. Wasp
DEPARTMENT MANAGER'S ENDORSEMENT
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OFFSHORE DEHYDRATION OF NATURAL GAS:
AN EVALUATION OF ALTERNATIVES
Traditionally the favorite process for offshore dehydration has been a triethylene glycol (TEG) unit utilizing a 4-8 tray absorber with bubble cap trays. These units work well and are relatively inexpensive. However, there has been an increasing concern about hydrocarbons emission from the vent gas and produced water over the last few years. The hydrocarbons of greatest concern are benzene, toluene, ethyl benzene, and xylene (BTEX). Units can be added on to mitigate the emissions but they take up extra space and weight which is expensive offshore. Therefore, there is an increased interest in decreasing the cost and size of conventional units or finding an alternative process that is less expensive. Under Gas Research Institute contract a survey of a number of offshore producers to determine present practices was conducted. Several absorber alternatives and/or modifications for conventional TEG units were compared with a hypothetical membrane unit for dehydration of 75 mmscfd of natural gas at 1000 psia and 100°F. Although commercial membrane units are not yet available a "good" hypothetical unit was compared because of its advantages of simplicity and lack of emissions. The membrane unit, however, was not found to be competitive. A TEG unit with a Higee™ absorber was found to have a slight advantage over more conventional trayed and random and structured packing absorbers after taking into account the effect of size and weight as well as initial cost.
SURVEY OF OFFSHORE PRODUCERS
A survey of seventeen offshore producers was performed to generate the following information: (Foral, 1994)
• Present offshore dehydration practices;
• Level of industry concern over emissions; and
• A design basis that would be typical of Gulf of Mexico offshore operating conditions.
Eleven companies responded to the survey indicating that the most commonly employed dehydration process used was TEG dehydration...