CCLP csi compressco lp - common units NASDAQ Oilfield Services/Equipment CLB core laboratories inc. NYSE Oilfield Services/Equipment ENSV enservco corp AMEX Oilfield Services/Equipment FI fiserv, inc. NYSE Oilfield Services/Equipment HAL halliburton company NYSE Oilfield Services/Equipment HLX helix energy solutions group, inc. NYSE Oilfield Services/Equipment NCSM ncs multistage holdings, inc. NASDAQ Oilfield Services/Equipment NGS natural gas services group, inc. NYSE Oilfield Services/Equipment NOA north american construction group ltd. common shares (no par) NYSE Oilfield Services/Equipment OII oceaneering international, inc. NYSE Oilfield Services/Equipment PUMP propetro holding corp. NASDAQ Oilfield Services/Equipment RCON recon technology, ltd. - class a ordinary shares NASDAQ Oilfield Services/Equipment RES rpc, inc. NYSE Oilfield Services/Equipment SLB schlumberger n.v. NYSE Oilfield Services/Equipment TUSK mammoth energy services, inc. NASDAQ Oilfield Services/Equipment WTTR select energy services, inc. class a NYSE Oilfield Services/Equipment