Natural gas processing in the Marcellus and Utica plays has quickly become a much larger—and more complex—business as major players race to keep up with fast-rising capacity needs and to ensure that the various elements of their infrastructure operate as an integrated, well-oiled “machine”. And, in a region with only minimal NGL storage capacity, one of that machine’s most important characteristics must be an ability to deal with all the “what-ifs” that could otherwise lead to logistical chaos, particularly those issues dealing with ethane. Today, we continue our in-depth review of Marcellus/Utica NGL infrastructure with a look at MarkWest’s innovative NGL network and distributed de-ethanization system.
In one of the most memorable TV scenes ever, Lucy Ricardo and Ethel Mertz, working as candy-factory wrappers in an episode of “I Love Lucy”, struggle as the conveyor belt accelerates, sending more and more chocolates their way (see it here). They cope (barely) through ingenuity (stuffing the candies they can’t handle in their mouths or storing them in their hats). MarkWest Energy Partners, which runs the largest natural gas processing and NGL-fractionation operation in the Marcellus/Utica, has been developing a far more elegant—and long-lasting—solution to dealing with the ever-increasing pace of gas and NGL production in that region. Most important, perhaps, MarkWest is building into its NGL network ways to mitigate the risks associated with producing NGLs in a region with next-to-no NGL storage capacity. That is particularly important for handling ethane, which is by far the most difficult NGL to handle when there are effectively no storage options.
As we said in Episode 1 of our series, in Mont Belvieu, TX, the center of the NGL/fractionation world, there’s plenty of storage to absorb infrastructure disruptions (like ethane-consuming ethylene crackers going offline or pipelines tripping off due to mechanical problems). But when similar disruptions hit the storage-challenged Marcellus/Utica (the January 2015 rupture of Enterprise Products Partners’ ATEX pipeline, which carries ethane from the Marcellus/Utica to Mont Belvieu, comes to mind) midstream companies need other ways to deal with all the NGLs still “coming down the conveyor belt”. In Episode 2, we described the Marcellus/Utica region in more detail; in Episode 3 we discussed the eight major pipelines that move natural gas through and out of the region; and in Episode 4 and Episode 5 we considered the gas processing plants, de-ethanizers and C3+ fractionation facilities MarkWest has been developing. (For more on what de-ethanizers and C3+ plants do, see Episode 5.) Today we’ll describe MarkWest’s innovative approach for integrating this infrastructure to handle the difficult issue of high-volume ethane production in a region with no ethane storage – and eventually to handle the requirement of petchem companies planning to build one or more ethane-based world-scale steam crackers in the region.
The Problem with Ethane
We’ve talked many times in the RBN blogosphere about the difficulties of storing ethane in anything but underground salt dome storage or moving ethane in anything but a pipeline (see Changes in Longitudes). Ethane has a boiling point of -127 degrees F, requires super-thick walled tanks to hold it, and is prohibitively expensive to move by rail or truck. Major NGL hubs like Mont Belvieu, TX and Conway, KS are built on top of salt formations that were developed into storage caverns (see Smoky and the Salt Caverns), and can easily handle ethane storage. But what about Marcellus/Utica where there is no salt storage? Well, the ethane could just be rejected (most of it is today) as we discussed in Back to the Ethane Asylum. That only works as long as the ethane rejected into the outlet gas stream does not make that gas too “hot”, meaning too high a BTU content for the take-away natural gas pipeline. And the more ethane you’ve got to handle, the more difficult that gets. Just a few years ago, MarkWest was trying to come up with a solution to that challenge for their Marcellus/Utica operation. Actually it was four challenges:
- They needed to be able to handle ethane demand outages – for both pipelines and the crackers to be eventually built.
- They needed to handle these outages (a) without violating the BTU specs of the pipelines that take away processed natural gas from their processing plants and (b) without the use of storage.
- They wanted to provide maximum flexibility for their producer customers to (a) elect to recover or reject ethane, and (b) take their ethane to whatever market they choose
- They wanted to do all the above using half as much de-dethanization capacity as would be required in a traditional fractionator configuration.
Could such an engineering feat be accomplished? You bet. Let’s see how they did it.