Just who is your fantasy buyer for the contracts the speculator wants to dump, just before expiration?
The buyer of a contract to take delivery could purchase a contract to deliver and thereby neutralize both.
There is exactly no shortage of buyers. In fact, the whole problem w/energy mkts these days is that there is an (artificial) shortage of sellers, not buyers.
Also, you don't use the tactic I described, called 'rolling', btw, ''just before expiration''. You use it starting 2-3 weeks before expiration, esp. if you're a big players, as witness these now-infamous ''index specs''.
Now, that said, a truly large index player would not (actually his bank would not, but let's keep it simple) dump 50,000-100,000 lots at one swoop; it would take 2-3-4 days, perhaps even up to 8-10 days, to accomplish the roll w/o too much price distortion.
See, the index specs just want to get and stay long in various futures mkts, the theory being that, by doing so, their entire portfolios are more 'balanced' on an asset-class basis. I happen to think that that is horse puckey; but, then again, it ain't my money.
Oh, one other thing. To the index specs, it's ''price no object''. They WILL be long, and damn the costs and the torpedoes. This attitude is one reason that energy pricing has become as out-of-whack as it is.