LONDON/HOUSTON (Reuters) – As oil and gas companies cut ever-deeper into the bone to weather their worst downturn in decades, boards have adopted contrasting strategies to lead them out of the crisis. Crude prices have tumbled around 70 percent over the past 18 months to around $35 a barrel, leading to five of the world’s top oil companies reporting sharp declines in profits in recent days. American firms Chevron (CVX.L) ConocoPhillips (COP.N) and Hess Corp (HES.N) are withdrawing from more costly deepwater projects to focus on shale oil fields on their home turf, for example.