Cairn expects bids for Rajasthan rigs by end-January

Vol 10, PW 19 (25 Jan 07) Exploration & Production

Cairn Energy is preparing an ambitious drilling programme to develop its discoveries at RJ-ON-90/1 in Rajasthan.

Cairn wants to begin production from the largest field Mangala in 2009 but meeting that target depends entirely on when it has a crude transportation and sales agreement in place. Nevertheless, tenders are out for three land rigs to begin development drilling.

Cairn expects bids in by the end of this month (January). Each rig will be hired for three years plus two â€کoptional’ years.

But Cairn might decide to hire these rigs for an initial, five-year â€کfirm’ period itself. Bidders have been asked to quote for both the three-year and five-year option.

If all goes well, Cairn wants to begin development drilling on 1st April 2008. These three rigs will be used to drill 292 wells at the Mangala, Bhagyam and Aishwariya fields.

Mangala will see 160 wells; Bhagyam 81 wells and Aishwariya will see 51 wells. Each well will take between eight and 20 days to drill, log, case and complete or suspend.

Most wells will be drilled to “shallow depthsâ€‌, that is up to 1000 metres, “but some horizontal wells are planned to even 2500 metres or more.â€‌ Bhagyam and Aishwariya are within a 20-km radius of Mangala field.

More than half of the first set of 160 wells will be on the Mangala oilfield and will be divided into two categories: آ· Type 1 wells will have 20-inch conductor casing pre-grouted at about 10 metres below ground level. The 17 آ½-inch holes will be drilled with water-based mud and 13 3/8-inch surface casing will be set at about 450 metres.

Oil-based mud will be used to drill 12 آ¼-inch directional hole sizes to about 1400 metres with 10.5-ppg mud weight. The 9 5/8-inch casing will be set at this depth آ· Type 2 wells will follow a similar casing programme till about 450 metres.

Oil based mud will be used to drill 12 آ¼-inch directional hole sizes to about 1500 metres and 9 5/8-inch casing will be set at that depth from where the well will be horizontal. An additional horizontal lateral section will be drilled to about 2200 metres and a 7-inch slotted liner will be run to this target depth

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