| 8. | Inventories, net |
| | | 2017 | | 2016 | | ||
| Crude oil | | | 1,836,363 | | | 1,557,267 | |
| Fuels and petrochemicals | | | 1,481,777 | | | 1,270,870 | |
| Materials for the production of goods | | | 1,283,256 | | | 1,013,764 | |
| | | | 4,601,396 | | | 3,841,901 | |
| | | 2017 | | 2016 | | ||
| Opening balance | | | 265,435 | | | 198,539 | |
| Additions | | | 9,134 | | | 41,957 | |
| Foreign currency translation | | | (4,266) | | | 50,053 | |
| Uses | | | (75,796) | | | (25,114) | |
| Closing balance | | | 194,507 | | | 265,435 | |