State-owned oil producers are planning to upgrade security arrangements protecting their oil installations in Assam following a series of bomb blasts on Thursday that left many dead and injured.

Oil and Natural Gas Corporation Ltd and Oil India Ltd have major presence in the state with an estimated annual production of 4.5 million tonne in 2007-08. Assam accounted for 12.76 per cent of India's total oil production.

"Surely, this situation will warrant serious thinking of extra security and extra surveillance," said ONGC's [Get Quote] chairman and managing director RS Sharma.

A senior Oil India official also said the company may ask for more security measures. "Although general security is in place, we may ask for more security according to our requirements," said the official.

However, both the officials claimed that existing security arrangements are well planned and geared to handle situations like this.

Security at ONGC's oil fields in Assam is provided by the Central Industrial Security Force, along with the company's internal security. Officials working at the company's fields in Assam say that security is currently good but can be better.

Oil production in Assam has often been interrupted with pipelines being blown up and oil fields being partially shut.

"We have always been facing minor problems. But there has not been anything major, and we want to prevent something major from happening," said an official with an oil company. Thursday's serial bomb blasts took place in lower Assam, while the oil fields are located in upper Assam.

"There have not been any terror attacks on oil installations in the past. But there is always the fear that it may," said one official working in the company's oil field in Assam's Sivasagar district.

The officials say that access to oil fields is very easy in Assam. "The rigs are right next to the road. Anyone can ride up and on a normal day would not be stopped," said another official.

But guarding the oil fields would require significantly more number of security guards. "And that is not always possible. The company has to provide for housing and transportation of the security forces and schooling of their children. This infrastructure, and the money, may not always be available," said the ONGC official.

Thursday's bomb blasts have resulted in increased vigilance, but no actual increase in the number of security men, officials say.

Oil India produced 3.5 million tonne of oil from its Assam fields between April and September 2008. In the whole of 2007-08, the company produced 3.1 million tonne of oil. ONGC produced 1.4 million tonne of oil in 2007-08.