Halliburton’s Kazakhstan operations reportedly violated customs laws by shifting imported equipment to operations that were not exempt from customs duties.

Halliburton, the world’s No. 2 oil services company, has worked in Kazakhstan for Agip, Kazakhoil Aktobe and Tengizchevroil (TCO), the joint venture between Exxon Mobil, Chevron Corp. and KazmunayGas. Agip and TCO are exempted from customs duties and taxes. Equipment brought in to the country as part of those companies’ operations is also exempted.

However, an audit by customs officials showed Halliburton imported goods that were being used on other projects, which resulted in the criminal case.

The company said it was cooperating with the customs investigation into its operations there.

Energy companies have flocked to Kazakhstan in recent years to take advantage of the country’s access to the Caspian Sea’s oil reserves.

The country accounts for about two-thirds of the Caspian’s 1.5 million barrels per day of oil production, and is estimated to have reserves of between 9 billion to 17.6 billion barrels.

Analysts have said they expect Kazakhstan’s oil production to reach 4 million barrels per day by 2020, with most of the production coming from the Tengiz, Karachaganak and Kashagan fields.

Much of the country’s oil is transported from Tengiz field to Russia’s Black Sea port of Novorossisk via the pipeline owned by the Caspian Pipeline Consortium.