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 AE adams resources & energy, inc. AMEX Oil Refining/Marketing CAPL crossamerica partners lp common units representing limited partner interests NYSE Oil Refining/Marketing GEL genesis energy, l.p. common units NYSE Oil Refining/Marketing GLP global partners lp global partners lp common units representing limited partner interests NYSE Oil Refining/Marketing MMLP martin midstream partners l.p. - common units representing limited partnership interests NASDAQ Oil Refining/Marketing NGL ngl energy partners lp common units representing limited partner interests NYSE Oil Refining/Marketing SUN sunoco lp common units representing limited partner interests NYSE Oil Refining/Marketing APA apa corporation NYSE Oil & Gas Production AR antero resources corporation NYSE Oil & Gas Production BRN barnwell industries, inc. AMEX Oil & Gas Production BSM black stone minerals, l.p. common units representing limited partner interests AMEX Oil & Gas Production BTE baytex energy corp common shares NYSE Oil & Gas Production CEI camber energy, inc. NYSE Oil & Gas Production CHK chesapeake energy corporation NYSE Oil & Gas Production CHKR chesapeake granite watr NYSE Oil & Gas Production CKX ckx lands, inc. AMEX Oil & Gas Production CNQ canadian natural resources limited NYSE Oil & Gas Production CPE callon petroleum company NYSE Oil & Gas Production CPG crescent point energy corporation ordinary shares (canada) NYSE Oil & Gas Production CRC california resources corporation AMEX Oil & Gas Production CRK comstock resources, inc. NYSE Oil & Gas Production CRT cross timbers royalty trust NYSE Oil & Gas Production CVE cenovus energy inc NYSE Oil & Gas Production DMLP dorchester minerals, l.p. - common units representing limited partnership interests NASDAQ Oil & Gas Production DO diamond offshore drilling, inc. NYSE Oil & Gas Production DVN devon energy corporation NYSE Oil & Gas Production DWSN dawson geophysical company NASDAQ Oil & Gas Production E eni s.p.a. NYSE Oil & Gas Production EC ecopetrol s.a. american depositary shares NYSE Oil & Gas Production EGY vaalco energy, inc. NYSE Oil & Gas Production EOG eog resources, inc. NYSE Oil & Gas Production EPM evolution petroleum corporation, inc. AMEX Oil & Gas Production EQT eqt corporation NYSE Oil & Gas Production ERF enerplus corporation NYSE Oil & Gas Production