One lesson we can take away from the miserable performance of the energy sector over the past year or so is that the cream rises to the top in times like this. In the case of oil services companies, it's pretty clear that Wall Street thinks Schlumberger (NYSE: SLB) is the best of the big oil services companies (adjusting for the fact that Baker Hughes (NYSE: BHI) is being acquired by Halliburton (NYSE: HAL), of course).

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But as is everything in investing, past performance does not ensure future results. So, investors that have a stake in Schlumberger should be on the lookout for a few key themes over the next several quarters to see if the company can continue to outperform its peers. Here are three things that investors should watch for in particular when Schlumberger reports its quarterly earnings on Oct. 15 after the market closes.

Where do revenue declines come from?
We can pretty much assume that with the decline in oil prices and overall oil and gas activity that Schlumberger and most oil services companies will see a major decline in revenue in the coming quarter. A consensus estimate from S&P Capital IQ says that Schlumberger's revenue for the quarter will be around $8.6 million, a decline of almost one-third from the same quarter last year. The bigger question will be where the bulk of those revenue declines come from.

So far, revenue on a product basis have declined rather equally, but geographically the big declines have been on from North America -- down almost 40% year over year -- versus international -- down 19%. This is expected since U.S. shale drilling is much faster to react to oil prices than larger development projects outside the U.S. and Canada. Compared to its peers, this trend actually benefits Schlumberger since it is less tied to the North American market than the other major oil services companies.

Company Decline in Revenue (year over year)
Schlumberger  25%
Halliburton (NYSE:HAL) 26%
Baker Hughes (NYSE:BHI) 33%
Weatherford International (NYSE:WFT) 36%

Source: 2nd quarter 2015 earnings releases.

Now that oil prices have declined for more than a year, though, it's possible that we could start to see larger declines in the international market as well. One place, in particular, to watch for potential declines is in its Reservoir Characterization segment. Last quarter the project backlog for its WesternGeco segment -- a component of Reservoir Characterization -- declined by 15% year over year. If work continues to dry up in this critical segment, we could see even larger revenue declines. 

Can it keep margins afloat?
To some degree, declines in revenue are out of Schlumberger's hands. If producers don't want to spend, then there is very little Schlumberger can do to replace that loss. One thing it has a little more control over, though, is its margins. 

The big things that will impact the company's margins will be its ability to maintain pricing power as well as make the necessary cuts to its operations to make up for the loss in revenue. So far, it has done rather well in comparison to its peers. 

Company Operational margin (Q2 2015) Operational Margin (Q2 2014) Change
Schlumberger  19% 21.7% -278 basis points
Halliburton  4.2% 14.8% -1060 basis points
Baker Hughes  2% 13% -1100 basis points
Weatherford International  4.9% 14% -910 basis points

Source: 2nd quarter 2015 earnings releases.

Just like Schlumberger's lower declines in revenue, much of the company's ability to preserve margins is from its higher exposure to the international market than the North American market like its peers. In fact, Schlumberger actually saw an uptick in its international margins last quarter. 

If the company can maintain its margins -- especially in the international segment -- then this coming quarter should look pretty good compared to its peers. 

A peek at the Cameron merger
Back in August, Schlumberger announced that it would acquire subsea equipment manufacturer Cameron International (UNKNOWN:CAM.DL) for $14.4 billion. At the time, it represented a pretty hefty premium to the price of Cameron's stock. But digging deeper, we can see an enterprise value to EBITDA ratio of 8.8 times for the purchase, so it's not that bad of a deal. 

Now that the price is set, the question is how well the company can translate that into improved performance across the company. The deal for Cameron isn't expected to be finalized until the first quarter of 2016, so it may be a little early to expect Schlumberger to issue anything like pro forma guidance on the deal. That being said, management is likely to discuss the deal in some detail. For investors, the big questions that need to be addressed are how the combined companies are greater than the sum of their parts. Can it fully achieve that estimated $600 million in cost savings? Are there some other impacts that could arise that haven't been addressed yet? Answering these kinds of questions will help to settle a lot of uneasiness shareholders showed when the deal was announced. 

What a Fool believes
So far, Schlumberger has been able to hold its head above water much better than many of its peers in the oil services space. A lot of that has to do with its more geographically diverse operations, but other moves such as its aggressive cuts to its workforce and other big operational cost cuts have helped keep profits buoyant. With oil prices hitting lows again in the third quarter, investors should see if the company was able to replicate its relative success. If so, it should bode very well for the future when oil and gas activity picks back up again.