Shell does not have to buy assets anytime soon, chief executive officer Wael ?Sawan said on Tuesday, as analysts and the company itself have said that the supermajor needs to fill a resource gap over the next decade. Shell needs an exploration breakthrough or a big merger after its oil reserves fell to the lowest levels since 2013, according to analysts. The so-called ‘reserve life’— denoting how long Shell’s proven reserves can sustain production at current levels—has dropped to below 8 years, significantly lower…