From the Document: "September 14, 2019, saw an attack on Saudi Aramco's, Saudi Arabia's national oil company, Abqaiq oil processing facility and Khurais oil field and processing plant. The attack, which used both missiles and drones, temporarily disrupted 5.7 million barrels per day (mb/d) of oil production, over half of Saudi Arabia's oil production and about 5% of global supply. For context, U.S. crude oil production is approximately 12 mb/d. [...] The incidents have demonstrated the vulnerability of critical Saudi infrastructure to missile and drone attacks and raised complicated strategic questions for Saudi and U.S. policymakers concerning responses and future security needs. On September 20, U.S. officials announced plans to deploy additional U.S. military personnel to Saudi Arabia and speed military equipment deliveries to Gulf partners to bolster capabilities and deter further attacks."
CRS Insight, IN11173
Congressional Research Service: https://crsreports.congress.gov/