Well, the SEC requires them to report...
... their income statement, balance sheet and cash flows. But they likely don't have to report at the level of detail of individual wells or even specific fields. That means they can obscure the production from specific wells by combining them with all others. That said, it shouldn't be all that difficult to get a good estimate by estimating revenues from wells that aren't confidential and subtracting that from the total reported to arrive at an estimate for the confidential wells.
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