With restoration of 37 wells over the last two years, Maersk Oil’s Danish Business Unit has made a step change in its work to restore and improve existing wells. This radical change both improves safety and protects production capacity. The work requires large investment, highly technically skilled people and supports employment in Denmark. The aim is to produce extra barrels safely and reliably for years to come.
Offshore platform in the Danish North Sea
Three drilling rigs are currently working full time in the Danish North Sea, two of which are restoring and protecting the operation of existing ones. This helps to unlock extra barrels of oil – as many as 10,000 barrels per day in 2013 – and safeguard existing reserves in a cost-efficient way.
”Our existing reserves from producing fields are just as important as finding and maturing new reserves. Drilling wells and building new facilities is costly, so we are allocating substantial resources to extracting more oil and gas from existing fields and wells,” says Lars Bo Christiansen, Head of Well, Reservoirs and Facility Management (WRFM) in Maersk Oil’s Danish Business Unit (DBU).
In the 1990s and 2000s many new wells were drilled in the Danish Underground Consortium concession area. With the completion of the Halfdan development in 2010, work on existing wells has been intensified.
“The wells require maintenance. After several years producing, they may need production tubing to be replaced due to corrosion or damage. This way we can raise the overall recovery from the reservoirs. Over the past two to three years, we have focused more on this area of business,” says Christiansen.
1. Lars Bo Christiansen, Head of Well, Reservoirs and Facility Management in Maersk Oil’s Danish Business Unit (DBU).
2. Niels Peter Steensberg Øgelund, Head of Drilling and Well Services in DBU.
RESTORING WELLS AND IMPROVING PRODUCTION
In the past two years, some 37 wells have been restored through the ‘workover’ process and are now producing more barrels. Examples of well management include: ‘cleaning’ scale out of wells through mechanical removal; ensuring efficient water flooding of reservoirs by flow testing wells regularly; and closing zones with high water production.
“One of the most important tasks at the moment is to replace production tubing in wells reaching the end of their life. Wells that have been producing for many years often have slowly corroding tubing. We are measuring the thickness of the tubing and, when necessary, conducting a workover. When fixed, the wells are normally good for many years,” says Niels Peter Steensberg Øgelund, Head of Drilling and Well Service Management in DBU.
Workovers are carried out from drilling rigs. And when you are managing drilling rigs, time is money. The rate for an appropriate rig in the Danish North Sea is around USD 350,000 a day, so the workover team is constantly trying to optimise their use.
“We now have two rig crews dedicated to workovers, so we can restore wells faster. However, each well job is different and requires good planning across the drilling, sub-surface and facilities departments. A simple job can take less than 20 days, and a more complex job may take over a month,” says Øgelund.
ACTING BEFORE WELLS CLOSE IN
DBU still has some wells shut in and waiting to be repaired.
”We have a number of plugged wells that need to be restored. The first step is to install new equipment and get these wells working again. The next step is to be proactive about workovers and replace tubing before it fails, so we can reduce both the number and duration of wells closed in. A simpler and quicker workover process will minimise the loss of barrels and boost production,” says Christiansen.
”We still have a lot of work to do, but we believe the programme has been a success so far. Last year alone we protected a potential 10,000 barrels per day that otherwise would have been locked in,” he concludes.
This programme of restoration on the well stock cost approximately DKK 1.3 billion (around USD 241 million) in 2013 and high costs are expected in 2014.