There's a trade-off with this debt-for-equity swap. Cash flow improves so there's less risk of a cash flow crunch that forces a drastic cutback in drilling activity and production. This reduces the downside risk in the stock. But the share count just increased substantially so the upside potential has also declined. WLL is now less financially leveraged and has less downside risk but also less upside potential.
I'm not sure what happened yesterday, but that plunge was a big overreaction to the news. Looks like some hedge funds shorted it super aggressively yesterday--just mauled this stock and triggered lots of stop orders. Unfortunately that kind of hyper-aggressive trading is allowed under the regulations, and it could happen again. Now we'll have to see what happens to oil prices. This stock has huge upside potential when oil moves back above $50 to stay.