Oil and Natural Gas Corp (ONGC) is mulling takeover of oil firm Transmeridian. The US firm has 211-million-barrel reserves in Kazakhstan.Transmeridian has been on ONGC Videsh's (the overseas investment arm of ONGC) radar for sometime now. The company has conducted preliminary due diligence and is expected to take a decision anytime now, industry sources said.The Houston-based company has a 100% interest in CaspiNeft, which holds the licence to the South Alibek field in Kazakhstan. The field is expected to produce 1 million barrels of oil per day.The AMEX Stock Exchange listed company is valued at over $1.5 billion by independent valuers.The sources said as per US law, OVL had two options to takeover Transmeridian - make an offer directly to company shareholders for purchase of shares or make a merger proposal under which 100% of the company is acquired with the board and shareholders approving OVL's offer.Transmeridian Chairman Lorrie T Olivier is the largest shareholder with an 18.4% interest.The South Alibek field constitutes a 14,111 sq km field in the northeast of the Caspian Sea in northwestern Kazakhstan, 380-km away from Tengiz.OVL currently has 26 projects in 15 countries with oil projects in Sudan, Russia, Columbia and Syria and one in Vietnam for natural gas.During FY08, OVL's share of production is 1.76 million tonne of oil and 0.519 billion cubic metres of gas.