Warren R. True
Pipeline/Gas Processing Editor
Respondents in gas gathering viewed improvements in compressor efficiency and multiphase metering as having the highest short-term impact and of being most likely to become commercial.
Among gas processors, respondents ranked separation of high impurities and trace constituents as having the highest impact followed by acid-gas removal and gas dehydration.
For respondents in gas storage, well-gas deliverability restoration and reservoir management ranked as high-impact technologies both short and long-term. Commerciality was expected to be achieved long-term.
Respondents were grouped according to industry segment: major oil and gas companies which implies major gas-transmission companies, independents, integrated oil and gas companies, and service companies.
Gas gathering
Under the broad term, the NPC seems to include not only field gathering but movements of natural gas via larger-diameter, cross country gas-transmission pipelines. All gas gathered from wellhead to plant inlet would be included.
For gas gathering, responses ranked compression improvements and multiphase metering to have the highest short-term impact and be most likely to become commercial (Fig. 1) (37293 bytes).
Compression improvement likewise will have the greatest impact in the long-term, which the study says reflects respondents views that the needs will not be met short-term.
Some examples of the kind of research that has been going on include low-cost NOx sensors, foundation block design, gas-turbine life extension, compressor efficiency, and software used in personal computers to diagnose compressor operation.
Multiphase flow refers to flow through field pipelines of gas that may also entrain quantities of oil, condensate, water, and sand. Multiphase metering and pumping have been subjects of several research and development efforts recently.
Most of the research has been based in North Sea countries and aimed at improving the economics of offshore production by reducing platforms' topsides equipment and locating separation and processing onshore.
As operators move into deeper waters in the Gulf of Mexico, the availability of multiphase metering at, say, a subsea wellhead and then of mixed flow into shallower waters for separation may make some fields economic which otherwise would not have been.
Other areas respondents identified for technology advances were improvements in leak detection, pressure ratings for plastic pipe, and high-pressure measurement.
Operators of small-diameter field gathering systems have long sought technological answers to problems of using plastic or composite pipe. The major barrier has been the unreliability of connections on plastic pipe.
The NPC study also published comments of respondents who wrote in areas that needed technology advances. Among these were several related to offshore gathering. These included development of a dry diverless pipeline-repair system and improvements in offshore laying and welding.
More than one respondent noted the need for improved hydrate control and removal and for improved measurement at low pressures and low volumes.
Gas processing
Among gas processors, no technology was identified overall as a key technology need. Several are very important to independents, however.
Respondents ranked separation of high impurities and trace constituents as having the highest impact followed by acid-gas removal and gas dehydration.
The study speculates that this may reflect respondents beliefs that new gas sources will contain more impurities and thus require more processing.
It is equally possible, however, that their keenly competitive and highly cyclical industry has made them more aware of the need to eliminate from operations all sources of potential damage to operations.
Several respondents expressed concern about hydrate control and removal. There was perceived to be a significantly higher short-term impact from advances in these technologies (Fig. 2) (35740 bytes).
Allied to this awareness of the need to run ever drier operations is the focus in recent years on reducing or eliminating sources of major pollutants that result from operating the most common gas-drying technology: glycol contacting towers.
Later this year or early next year, the U.S. Environmental Protection Agency will issue a final rule affecting thousands of glycol reboilers at nearly every gas processing plant and many gas field gathering sites in the U.S. A reboiler regenerates hydrate-saturated glycol by driving off the water and recirculating the glycol to a contactor tower.
In the past, the vent stack of a reboiler has been a source of such EPA-identified pollutants as benzene, ethyl-benzene, toluene, and xylene, collectively called BETX. In addition, other volatile organic compounds (VOCs) are emitted.
Research in the U.S. has intensified in recent years in efforts to reduce or eliminate the emissions from reboilers.
As Fig. 2 (35740 bytes) shows, respondents felt all the technology areas about which they were asked were likely to reach commerciality by 1999.
Some comments that accompanied returns, however, expressed some impatience with the pace of technology development in gas processing.
The following is typical: There have been, wrote one respondent, "very few technological advances in areas like acid gas treatment [and] hydrocarbon separation.... Amino gas treatment technology has not changed essentially for 70 years plus. The latest in hydrocarbon separation was cryogenic processing which began in the late '60s."
Among other areas cited in comments as needing technology advances were smaller-scale liquefaction for remote or offshore applications and more accurate, dependable measurement.
Gas storage
For respondents in gas storage, well-gas deliverability restoration and reservoir management ranked as high-impact technologies both short and long-term. Commerciality was expected to be achieved long-term.
Short-term, base-gas minimization techniques ranked very high, reflecting the large dollar commitment required, says the study (Fig. 3) (34419 bytes).
Although more respondents (13) listed well-deliverability restoration as a technology need, they seemed to feel it was unlikely to become commercial in the short term: it ranked lowest in this regard.
Technology related to inert base-gas research ranked lowest for likelihood to become commercial short-term. The category refers to research into using a gas that is less volatile to handle and of less value on the market place to provide the cushion in a cavern over which the stored natural gas is placed. This latter is referred to as "working gas" and is that which is withdrawn or injected seasonally.
Major-company respondents rated as least likely to be developed both short-term and long-term technologies related to inert base-gas research. Respondents from integrated oil and gas companies also rated this in short-term as least likely to be become commercial.
Most likely to become commercial either short-term or long-term, said major-company replies, were technologies dealing with well-deliverability restoration.
Base-gas minimization is important to operators because that is an amount of gas that has potential value in the market place but which must be kept in a reservoir to maintain delivery pressures as well as, in some instances, cavern-wall integrity.
Other concerns related to gas storage listed by respondents included better injection/withdrawal metering, improved monitoring and automation, and information on the effect of gas temperature in salt-cavern storage. Copyright 1995 Oil & Gas Journal. All Rights Reserved.
