Statoil’s Drilling & Well (D&W) team has recently delivered three new wells on the North Sea Snorre B field, contributing strongly to the Norwegian company’s corporate goal of “radical change” to reduce the break-even for new wells. The three wells, C-2, C-3 and C-4, have boosted Snorre B production by 30%.

“We estimate the price per barrel for these wells to be well below US$10 (£8),” says Oddmund Rismyhr, acting head of Snorre PETEC (Petroleum Technology). “Snorre B is currently producing around 80,000 barrels per day, which is a very satisfactory result. Together with D&W we have found the right drilling targets for our wells, and when we add a predictable and long-term drilling plan allowing optimisation and higher efficiency, we have the success factors.”

According to Johan Dahl, head of D&W planning, the poor condition of the slots led Statoil to adopt a simplified casing design for one of the wells. To cut costs, the company also implemented a standard, simplified completion design for all the wells with the same type of drilling fluid in each case to allow re-use.

In addition, managing the operations – drilling, lower completion, upper completion and christmas tree setting – in series for the three wells saved rental time and resources.

RENT
“If we drill only one well, we must rent equipment and send it back to shore, while the remaining completion equipment and drilling fluid must be sent to shore when we are done,” explains Dahl. “In this case we did the same operations three times, saving much time, improving use of resources and reducing costs and rental time. We also saved a lot on mobilisation costs and logistics.”

He adds: “At the same time we learnt a lot from each well, which is reflected in the reduction in time spent on sub-operations during the process.”

Dahl points out that good cooperation between D&W and PETEC allowed weather considerations to be included in the planning. Normally, he says, 35% of time is spent on waiting on weather during the months of the year with the most demanding weather conditions. Operations in bad weather often lead to major downtime incidents. This was avoided at Snorre B and consequently the operations succeeded at their first attempt.

“Earlier we wanted to start production immediately, and it was therefore not considered to adapt operations to the weather conditions,” says Dahl. “But we realised that when we make a good plan that takes this aspect into consideration and has a long-term perspective we achieve higher production sooner than we did before. If we had operated like we did in the old days, we would not have been able to deliver more than two of these three wells, with the starting point we had at that time.”

REFERENCE
For the D&W team on Snorre there is only one reference base that matters. “We are only looking at how close to a ‘perfect well’ we can get,” says Ilhan Løwen, drilling superintendent of D&W.

This is calculated by combining the best sub-operations completed in wells previously into a fictitious reference well.

 
“We have made it a little difficult for ourselves by including reference wells from the field start-up, all the way back in 2001,” Løwen continues.

The “perfect well” time expenditure for C-4, C-3 and C-2 was 49, 46 and 69 days respectively. The actual time expenditure was 58, 58 and 91 days. The costs were NOK 168, 149 and 193 million (£15.1, £13.4 and £17.4 million). The average price in the period 2009-2013 was NOK 490 million (£44.2 million).