The fractionation and NGL storage complex in Mont Belvieu, TX, would surely qualify as one of the Seven Wonders of the Energy World, if there were such a list. With more than 250 million barrels of NGL storage carved — by water! — out of an enormous subterranean salt dome formation, and nearly two dozen fractionation plants with a combined capacity of more than 2 MMb/d, Mont Belvieu not only serves as the largest receipt point for mixed NGL streams on the planet, it is also the key hub of distribution for the ethane, propane, normal butane and other NGL purity products that are either consumed by Gulf Coast steam crackers and refineries or exported to foreign end-users. But unlike wonders of the ancient world like the Great Pyramids at Giza, Mont Belvieu is still very much a work in progress, with new storage caverns and new fractionators now under development to try to keep up with the breakneck pace of U.S. NGL production growth. Today, we begin a company-by-company review of fractionation capacity and other key infrastructure there.
In Part 1 of this blog series, we discussed the current state of the U.S. natural gas liquids (NGL) sector. The condensed version goes like this: NGL production in the Permian, the Marcellus/Utica, the SCOOP/STACK and other key basins is rocketing higher, with potential U.S. NGL production from natural gas processing plants — including ethane that is rejected into natural gas — now approaching 5 MMb/d. A number of new, ethane-consuming steam crackers are coming online along the Texas and Louisiana Gulf Coast, conveniently close to the NGL storage and fractionation hub in Mont Belvieu. The export market for liquefied petroleum gases (LPG) — mostly propane but some normal butane — is through the roof too, averaging more than 1 MMb/d in the first five months of 2018 (almost all of it being shipped out of Gulf Coast ports), and ethane exports are strong as well. And, with the rapid run-up in U.S. NGL production — combined with some reluctance of producers to commit to new fractionation capacity — the existing fractionation plants in Mont Belvieu are running flat-out to keep up. More fractionation capacity is needed ASAP.
We also provided an introductory “magical mystery tour” of Mont Belvieu itself. When standing in Mont Belvieu, under your feet is the huge salt dome formation (two miles wide and six miles deep) and the big storage caverns that have been created within it using “solution mining.” Each cavern is always filled to its brim with some brine (salt-saturated water) and some hydrocarbon product — in other words, a well whose volume is 20%-filled by brine will be 80% filled by, say, mixed NGLs (y-grade) or a purity product (ethane, propane etc.). Because brine has a greater density than liquid hydrocarbons, the y-grade or purity product “floats” on top of the brine. The piping in a typical storage cavern consists of a larger-diameter pipe that extends from the surface to just past the top of the cavern, and a smaller-diameter pipe installed concentrically within the larger pipe — this skinnier pipe extends from the surface to just above the bottom of the cavern. When liquid hydrocarbons are pumped into the top of the cavern through the annulus — the space between the small pipe and the large pipe — brine is forced out from the cavern's bottom via the smaller-diameter pipe into a brine pond on the surface. To withdraw NGLs or purity product, brine is pumped into the bottom of the cavern to force out the liquid hydrocarbons up top. All around you on ground level (interspersed among the brine ponds, or pits) are fractionation plants, which separate y-grade into purity products. Because each purity product has a boiling point that is sufficiently different from the others, they are separated by the sequential “boiling off” of ethane, then propane and then butanes, leaving you with natural gasoline. Mixed butanes then can be separated into normal butane and isobutane in a de-isobutanizer — a word that (by the way) would give you a staggering 26 points in Scrabble (78 if you cover a “triple word score” square with one of your tiles).