SINGAPORE (Reuters) – Oil prices slipped on Monday after China posted its slowest quarterly economic growth in at least 27 years, reinforcing concerns about demand in the world’s largest crude oil importer. A horizontal drilling rig on a lease owned by Parsley Energy operates at sunrise in the Permian Basin near Midland, Texas U.S. August 24, 2018. REUTERS/Nick Oxford Brent crude futures LCOc1 for September fell 15 cents, or 0.2%, to $66.57 a barrel by 0611 GMT while U.S. crude CLc1 for August was down 24 cents, or 0.4%, at $59.97 a barrel. Both contracts last week posted their biggest weekly gains in three weeks on cuts in U.S. oil production and diplomatic tensions in the Middle East. Refineries in the path of Tropical Storm Barry continued to operate despite flood threats while the storm has slashed U.S. Gulf of Mexico crude output by 73%, or 1.38 million barrels […]