Even with a change in laws that allow for exports, total U.S. crude oil imports increased with net gains coming from OPEC nations, government data show.

The U.S. Energy Information Administration reported crude oil imported into the East Coast market increased 41 percent last year, with nearly 75 percent of that coming from Nigeria. While Nigerian crude oil production declined in part because of conflict targeting the energy sector, Nigeria's oil was more cost competitive and lower crude oil prices meant less oil was coming from domestic basins.

"As a result, imports from Nigeria, which had fallen from more than 1 million barrels per day in 2010 to only 7,000 bpd during the first half of 2015, were able to partially return to their former primary market in the East Coast, rising to 186,000 bpd during the first half of 2016," an EIA report read.

On a net national basis, crude oil imports into the United States increased 7 percent during the first half of the year when measured against the same period in 2015. This marks a stark contrast to the historic trends of declining U.S. imports that came as a result of the increase in production that was driven by an oil price two years ago above $100 per barrel.

The increase in total U.S. crude oil imports is the first since increase in six years. On a national basis, shipments from Nigeria, Iraq, and Canada contributed most to increased imports.

EIA said the difference between the price for various crude oil grades in the United States and those overseas had narrowed in part as a result of a change in laws that allowed for U.S. crude oil exports.

"The narrowing differences between certain U.S. crudes and international benchmarks provided an incentive for increased imports by refiners in areas where imported crudes now had a delivered cost advantage relative to domestic crudes of comparable quality," the EIA's report read.

A report published in July by the Norwegian government found strategies from OPEC to defend a market share may have led to a decline from rival producers. The report from Statistics Norway found OPEC behavior "probably" limited the role of U.S. crude oil.

Last week, however, OPEC backed a proposal to hold production levels static in an effort to lift crude oil prices. Crude oil prices since that agreement was reached are 15 percent, or about $5 per barrel higher, and may be moving to the point that U.S. shale oil producers re-examine their opportunities.

Sen. John Hoeven, a Republican from the oil-rich state of North Dakota, admitted robust production policies from OPEC members curbed U.S. oil potential. He supported an end to the export ban, arguing it would boost the U.S. energy economy while increasing leverage overseas.