By Kevin Crowley and Meenal Vamburkar, Bloomberg It’s not exactly the Pike’s Peak gold rush of 160 years but with crude prices on the rise, explorers are returning to the oil-rich rock of Colorado as a way to expand beyond the shale plays of Texas and New Mexico. During the three-year crude-market collapse, as prices fell below $27 a barrel, the Denver-Julesburg Basin northeast of Denver was largely abandoned as explorers tightened down drilling budgets.