- MOL (Hungarian Oil Company) – Hungary
- INA (Croatian Oil Company) – Croatia
- CROSCO Drilling Co. – Croatia – Croatia/Syria
- NEMMOCO Co. – Slovenia
- NIS (Serbian Oil Company) – Serbia
- GAZPROM – Astrakhan, Russia
- TESCO Co. – Calgary, Canada
- ROTARY Drilling Co. – Hungary / Syria
- MB Group – Hungary / Oman
- Hungarian Horizon Energy Co./ CED – Hungary / USA
- TOREADOR Hungary Co. – Hungary / USA
- MATRA Blue Star Co.– Hungary
- PETRO Hungaria Co. – Hungary / Great Britain
- EON Gas Storage Co. – Hungary
- Geoinform Ltd. – Hungary
- BJ Rotary Ltd. – Hungary
- TDE Ltd. – Hungary
- OEOC – Iran