• Willbros Downstream of Oklahoma, Inc.
• Willbros Downstream, LLC
• Willbros Energy Services Co
• Willbros Engineering California (U.S.), Inc.
• Willbros Engineers (U.S.), LLC
• Willbros Government Services (U.S.), LLC
• Willbros Midstream Services (U.S.), LLC
• Willbros Project Services (U.S.), LLC
• Willbros Refinery & Maintenance Services (U.S.), LLC
• Willbros T&D Services, LLC
• Willbros United States Holdings, Inc.
• Willbros Engineers, LLC
• Chapman Construction Co., L.P.
• Platinum Pressure Pumping, Inc.
• Admiral Well Service, Inc.
• Maverick Coil Tubing Services, LLC
• Maverick Solutions, LLC
• Maverick Stimulation Company, LLC
• Maverick Thru-Tubing Services, LLC
• MCM Holdings, LLC
• Maverick Companies, LLC
• MSM Leasing, LLC
• Platinum Pressure Services, Inc.
• Taylor Industries, LLC
• FTS International Inc.
• Forbes Energy International, LLC
• Nine Energy Service Inc.
• Seventy Seven Energy Inc.
• Superior Energy Services Colombia, LLC
• HECKMANN WATER RESOURCES Corp
• Heckmann Water Resources (Cvr), Inc.
• Green Field Energy Services, Inc.
• U.S. Well Services, LLC
• Chesapeake Oilfield Services Inc
• Advantage Disposal Solutions, Inc.
• Emergent Energy Services LP
• Armada Water Assets Inc
• Schlumberger Investment SA
• Expro Group Holdings N.V.
• Mammoth Energy Partners LP
• King Merger Sub II LLC
• CEBA Midstream, LP
• Quintana Energy Services LP
• U.S. Well Services Inc
• Mammoth Energy Services Inc.
• ProPetro Holding Corp.
• NexTier Oilfield Solutions Inc
• NCS Multistage Holdings Inc.
• Select Water Solutions Inc.
• Liberty Energy Inc.

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