Cairn India which is exploring for oil in Sri Lankan waters is to start gathering meteorological data and monitor ocean currents next month ahead of a test drilling programme.

The sub-contract for the 'metocean and currents survey' in the Gulf of Mannar is to be awarded soon, said Neil de Silva, head of Sri Lanka's petroleum resources development secretariat overseeing exploration efforts.

Cairn India is to drill three test wells before October 1, 2011 according to their work programme.

The firm has completed three-dimensional (3D) seismic surveys of its exploration block in the Gulf of Mannar and is now processing the data to identify drilling locations.

Cairn India said in a recent statement the 3D seismic survey started in December has been completed and it acquired 20 percent more than the 1,450 square kilometers required under its Minimum Work Programme.

The 3D seismic data acquisition was done by Compagnie General de Geophysique Veritas (CGGV), a large international seismic contactor.

3D seismic data produces a cube of data which greatly enhances the understanding of the geological sub surface and improves the chances to discover oil and gas deposits, Cairn India said.

The firm is to complete 3D seismic data processing and interpretation by about November this year and finalize a drilling rig contract before December.

Drilling of the first test well is to start in the first half of 2011, by about April, in what Cairn India called an "extension of proven hydrocarbon play" in the Cauvery and Gulf of Mannar region.

This refers to oil deposits already found on the Indian side of the same seabed geological structure.

The company is looking for oil in a 3,000 sq km block in deep water ranging from 400 metres in the east to about 1,900m towards the west.