Centek Group’s S2 centralizer has been run highly effectively in shale rock completions in the USA. The S2 has been used for oil extraction in shale plays in Colorado’s Niobara formation in the DJ basin and the Bakken formation in North Dakota and Montana. These formations are narrow, and lenticular, where it is most effective to drill horizontally. The Bakken is among the most important US shale formations with estimates of 3 – 4 billion barrels of recoverable oil.
The S2 has proved itself valuable in two instances. On the intermediate casing string where the drill team is building the curve to go horizontal, they run the S2 through the curve, and then on the horizontal production string, which in the DJ basin is 3,000 – 7,000 feet extended reach, and in the Bakken wells 10,000 – 12,000 feet of horizontal reach.
In shale oil plays getting to bottom requires extended reach horizontal completions, and involves using swellable rubber packers to isolate the zones and a drop sleeve system to selectively open and fracture the formations, with possibly 20–30 separate zones. Given the cost of around $1.5 million on a 10,000 foot completion string getting to bottom without problems is vital. As there are no perfectly drilled holes and the hole is likely to be deviated in the horizontal it becomes much harder to push the casing to bottom than in a standard vertical application. As the drill team leads each rubber swell packer into the hole, they run an S2 centralizer ahead of every swell packer which has enabled them to get the packers to bottom, and importantly, to bottom undamaged.