It has been a good run, but now it's time to part ways. Marathon Oil (MRO -0.81%) is going to sell its North Sea assets in Norway and the U.K., which could fetch $3 billion according to UBS Investment Research.

By shedding these assets, Marathon Oil can focus on what really matters: America. With more cash being devoted toward this great country, Marathon Oil will be able to double 2013 output to ~160,000 boe/d in the Eagle Ford by 2017.

America's favorite bird
Every patriot loves the American bald eagle, and Marathon Oil is no exception. Due to Marathon Oil's strategic repositioning, it will increase drilling activity in the Eagle Ford by 20% this year. The Eagle Ford is a liquids-rich play with access to Louisiana Light Sweet pricing that should propel margins higher, likely resulting in larger cash flow.

Part of Marathon Oil's cash flow growth is going straight back into the business. Marathon's capex increased to $5.9 billion this year, as compared to $5.2 billion last year. While the Eagle Ford is going to receive a shot of adrenaline, two other shale plays will also experience more investment.

No oil producer is complete without some exposure to the Bakken, and Marathon Oil is no exception. 2014 will see drilling activity increase by 20% on Marathon's acreage, just like in the Eagle Ford. Also like in the Eagle Ford, output is expected to roughly double by 2017.

In the Anadarko Woodford Basin, Marathon Oil plans on doubling down by increasing its drilling activity by 100% this year. Over the next few years, that will triple output and provide a better liquids production mix. This gives Marathon Oil three different plays to reward investors with. Overseas, Marathon would have never found growth like this. 

Taking notes
Marathon Oil isn't alone in its domestic oriented strategy. Apache (APA -0.54%) also sold off a $3 billion -- $2.95 billion to be precise -- stake in its Egyptian assets. By selling a minority stake to Sinopec (SHI), Apache freed up significant amounts of cash to work on developing the Permian and Central plays back home. While Apache will still operate the upstream business, it wants to grow onshore North American production.

In the course of just under four years, Apache has grown the portion of its production from North American onshore assets to 56% from 32%. Along with this came even better news: the production mix shifted toward higher margin liquids. In that same time period, liquids grew to 55% of output from 50%.

So far, Apache's plan has worked wonders; 94% of its 201,000 boe/d production growth came from onshore North American plays since 2009. Now Apache is pumping out almost 800,000 boe/d, and there is no reason to believe that growth will stop.

Apache has divested $7 billion in assets to focus on shale plays in America, primarily in the Permian Basin. Output is already exceeding expectations from the play, which should continue as more capital is allocated to the area.

Apache loves Texas
Shale plays have allowed Apache to grow its proven reserves to 2.9 billion barrels of oil equivalent. 37% of that is located in the Permian Basin and Central area, but 85% of Apache's 11.7 billion boe in potential reserves lies within those two regions. If it's given the chance to fully develop the region, a market cap of $34 billion would imply you are buying a barrel of oil equivalent for just under $3.

The value proposition seems promising, and one that would never have materialized had Apache not divested non-core assets to focus on Texas.

Foolish Conclusion
In a free market, the best acreage wins out. Marathon Oil and Apache were smart to sell off assets in areas not living up to investors standards, and instead turning toward the good ol' US of A.

By selling off foreign assets, both oil producers can direct additional capex to shale plays and use the extra cash to pay down debt, invest further in growth projects, or buyback shares. I applaud both company's for their change of heart and I hope investors do the same.

America's oil and gas production could be trouble for OPEC