For the first time in almost two decades, the North African nation is reopening its oil industry to foreign investors. The timing is exquisite: The major oil companies are on the lookout for opportunities to replenish their reserves, aiming for projects that might come on stream in the 2030s. With more than 50 percent of Africa’s oil reserves, the region’s geology offers high-quality crude that is cheap to produce, plus significant gas fields. Last year, it pumped about 1.3 million barrels a day, well above its post-civil war low point but still below the most recent peak of 1.8 million barrels a day set in 2008. Only time will confirm whether oil companies can find new reserves and manage to develop them into commercial oil and gas fields.