By comparison, Saudi Arabia produces 12 million barrels of oil a day: if the price drops $30 they need to make $360 million per day to cover that, or $30 billion if they carried out the trade over a three-month period.
If the total single-name CDS market is $10t and $1t of that is in oil and gas firms...it doesn't seem out of the question you could get a $30b position. Not that I really believe this is what's going on.