Big Oil is today in a spending sweet spot as years of cost cuts and rising oil prices converge but investments will need to rise after 2020 to boost output, BlackRock, the world’s largest asset manager, said on Tuesday.  Oil and gas giants such as Royal Dutch Shell ( RDSa.AS ), Chevron ( CVX.N ) and BP ( BP.L ) are generating as much cash at today’s oil prices of around $70 a barrel as they did in 2014, before crude spiraled down from over $100 a barrel to lows of below $30 a barrel. As they emerge from the deepest downturn in decades, boards have vowed to remain thrifty and stick to lower spending targets in order to […]