Investment in the U.S. shale sector will drop by half this year, the International Energy Agency said Wednesday, predicting a period of pain for producers, even as oil prices rally. The forecast body-blow to the availability of capital for U.S. producers comes as part of an expected world-wide decline in broader energy investment during 2020. The Paris-based organization expects global investment in oil and gas to decrease by a third and the financing of all energy projects to decline by 20%. …