Big Oil is facing a tough week of third-quarter earnings reports

• BP reports Tuesday; Total SA reports Wednesday; Royal Dutch Shell's comes Thursday; and U.S.-based giants Exxon and Chevron arrive Friday.

Threat level: Per Bloomberg, the companies are expected to post an average 42% drop in earnings.

• That decline stems not only from oil prices, but also weakness in the petrochemicals market, maintenance keeping facilities at below capacity, and other forces.

But, but, but: It's not just the biggest multinationals facing a tough earnings season.

• "Investors are bracing for weaker results from U.S. shale players in coming days as lower oil and natural gas prices and cost-cutting measures have weighed on third-quarter operations," Reuters reports.

Go deeper: Big Oil's Q3 lobbying numbers