DeltaTek Global runs successful first outing for its SeaCure cementing tool
Cementing offshore wells is not something that operators readily want to experiment with (the ghost of Deepwater Horizon haunts innovators), but Aberdeen’s DeltaTek has developed a new system covered by around 40 patents that offers a significant saving in rig time and also a higher quality cementing job. The system is named SeaCure.
Traditional cement jobs leave a long cement plug on the shoe – 10-30 metres – at each cementing stage. If a well is to be cased and cemented using SeaCure the driller first fits a SeaCure shoe unit to the end of the casing – the shoe is about a metre long. This unit is a steel cylinder into which SeaCure fits its proprietary assembly of non-return valves and a unique latchable float shoe. The assembly is held in place in the cylinder by a fill of cement aggregate, which provides rigidity and also serves as the seal for the coming cementing job.
Once in place at the target depth SeaCure runs an inner drill string that latches securely into the top of the shoe. Cement is run down the drill string, through a double non-return valve in the float shoe and into the annulus.
When the required volume of cement has been pumped the next step is to seal off the top of the shoe from the casing, so that a pressure test can be run. To do this SeaCure sends a wiper dart the inner string, to lock into the top of the float shoe. The shoe therefore becomes a complete seal in both directions.
The inner string naturally pressurises once access to the shoe is closed, and three rupture discs above the dart break, allowing seawater to fill the casing to the surface. The casing’s seabed valve is closed, pressurising the casing. Once the pressure test is complete the inner string unlatches from the shoe and is pulled. Drilling restarts, but now with only a metre or so of elastomers, aluminium and the light cement fill in the shoe to penetrate.
Time saved depends on how much cement plug drilling has been avoided, but SeaCure estimates that at least eight hours of rig time is saved per shoe, and in some cases a day.
Because the consequences of failure are so severe it is usually very difficult for a small innovator (Deltatek currently has four, going on six, staff) to persuade operators drilling multi-million pound wells to try out new techniques. Deltatek enlisted the Oil and Gas Technology Centre to help it persuade Chevron to give SeaCure a test run in its West Wick appraisal well, drilled from the Ocean Guardian, in 2018.
Here, SeaCure was used to cement a 30-inch conductor. The test run was a complete success, saving eight hours of rig time, according to a Chevron spokesperson.
Looking ahead, SeaCure is booked to work in Energean’s Karish field in the Eastern Mediterranean, and for several other Mediterranean wells in the first half of 2019.
“The concept is well proven onshore and almost exclusively used as the method of getting cement to the right place, by using a stabbed-in inner string. Before SeaCure, operators and drilling contractors had used various other, less accurate, methods such as using poor boy inner strings or SSR plugs with shoetracks when building the well,” said Dave Shand, CCO.
Apart from cost-cutting, SeaCure brings a soft win too – less risk of contamination of the cement job. SeaCure is planning to self-fund the next stage of its business growth from sales.