Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

Oil dropped $1.60, or 1.6%, in late trading today, falling below the $100-per-barrel level once again. But stock investors aren't seeing that as a bullish sign for the market as a whole. Stocks are flatlining today, with the Dow Jones Industrial Average (DJINDICES:^DJI) up a forgettable nine points as investors wait for September's jobs report, due tomorrow morning. There are also a number of big earnings reports due this week, including Netflix, Boeing, Microsoft, and Amazon.com. Look for those to drive the market along with the jobs report, starting tomorrow.

Growing U.S. oil stockpiles were behind the price drop. The Energy Information Administration said crude-oil supplies grew 4 million barrels for the week ended Oct. 11 -- the fourth straight week of gains. The market is dealing with booming supplies from shale drilling and lackluster consumer demand for oil because of more efficient vehicles and people driving less overall.

Growth in production has been a mixed bag for oil companies, but it's generally a good sign for service providers. Baker Hughes (NYSE:BHI) and Schlumberger (NYSE:SLB) jumped last week after reporting 8% and 11% increases in revenue, respectively, driven by offshore demand in the U.S. and abroad. But today, Halliburton (NYSE:HAL) fell 3% after reporting its own third-quarter earnings. 

Revenue was up 5.1% to $7.47 billion for Halliburton, but it fell just short of the $7.5 billion Wall Street expected. The primary challenge is that drilling in the U.S. has become more efficient, requiring less equipment time. So while U.S. production is increasing, rig count isn't.

Baker Hughes and Schlumberger saw similar trends in their earnings releases but relied on growth in offshore drilling to offset lower domestic onshore demand. Halliburton even put a cost reduction plan in place, which included undisclosed layoffs. Shale drilling is big business but Halliburton is seeing a slowdown in demand for some of its equipment, just like the rest of the industry.

Speaking of shale drilling, Chevron (NYSE:CVX) may be giving up on such efforts altogether in Romania following regional protests. Hundreds of demonstrators turned out after the company began drilling in the village of Pungesti. Local officials said they would hold a nonbinding referendum on Nov. 24 on Chevron's drilling, so the company is in a holding pattern until then.  

Shale drilling is seeing a lot of challenges, and investors should be careful where they're placing their bets because areas like offshore drilling may have better odds for earnings growth at the moment.

Fool contributor Travis Hoium has no position in any stocks mentioned. The Motley Fool recommends Chevron and Halliburton. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.