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By eliminating tripping for installing and removing plugs, and perforating, companies can cut the time for hydraulic fracturing dramatically.
Imagine being able to cut the amount of time it takes to frac a well from the normal 40 to 50 days in the North Sea to 1.5 days. That’s what well-technology company i-TEC Well Solutions achieved recently on the Norwegian continental shelf.
The company’s unique, new, lower-completion, ball-drop sleeve system, called “i-Frac,” allows operators to bring wells in tight formations on line much more quickly than other methods, resulting in potentially huge cost savings and earlier production revenues, according to i-TEC.
The system has also been used in the U.S. in both the Bakken and Woodford shale plays, Al Wilkins, i-TEC’s North American sales manager, told Hart Energy E&P Online.
The ball-drop, sleeve system replaces the common “plug-and-perforate” technique, eliminating trips to prepare each zone for being hydraulically fractured.
In the U.S., where the demand for fracing crews often exceeds the supply, being able to cut the frac process from say eight to two days, in effect, quadruples the number of wells a single frac crew can complete.
The system uses a series of balls pumped through the completion string to open valves that allow access to the formation. The i-TEC system can be run in cemented as well as open hole applications. More than 20 sleeves per stage can be installed in a cemented liner and opened sequentially with a single ball. Up to 22 stages can be run. The number of valves per stage can be varied to suit conditions. The well can be completed in a single, continuous process with the additional environmental benefit of a reduction in water use.
|More than 20 sleeves per stage can be installed and opened in each zone by pumping a ball down the production string. (Illustration courtesy of i-TEC)|
Once the completion string is run and the casing cemented, a conventional cementing dart is run to clean out the casing and seats in the toe of the completion. After the cement is set, a pressure integrity test is performed. This test also initiates the i-Fill opening sequence. The i-Fill is a pressure activated toe sub.
Pressure is cycled, which finally opens the i-Fill. An increase in pressure breaks the cement behind the i-Fill, allowing communication to the formation. Flow is increased to insure a good flow. Then, the smallest i-Frac ball is dropped and each sleeve in the first stage is opened sequentially. The lowermost sleeve retains the ball providing a seal. An increase in pressure causes the cement outside the open valves to break down and that stage is fraced.
|Pressure is cycled to open the i-Fill, pressure-activated toe sub, allowing communication to the formation. (Illustration courtesy of i-TEC)|
The next ball is dropped, and so on, until all of the stages are opened and fractured. Once all stages are fractured, the formation is allowed to flow.
On the Norwegian shelf, i-TEC opened 56 valves in three zones by dropping only three balls. The different sized balls were pumped into the well to open all the valves in each zone. This technology also enables the inclusion of a far greater number of valves as compared to alternative solutions.
The recent installation was in Early Paleocene and Late Cretaceous carbonate formations in the Norwegian sector of the North Sea.
The technology also has huge potential for global shale oil and gas plays, particularly in the United States, where in some tight shale fields it could allow an operator to fracture twice as many wells in a year compared to traditional methods.
“We’re looking at one well with 106 valves in the Eagle Ford,” Wilkins said. “Now, 30 to 40 zones in the Bakken is normal. One to one-and-a-half years ago, that was impossible to do.”
“Time is money. Dropping the balls takes far less time than running the plug and the perforating guns for each zone.” he added.
Recently, the wait time for a frac crew in the Bakken could be as long as three to four months. “When you do get a frac crew, you frac in as short a time as you can. That also benefits the frac companies who can increase utilization of their crews and equipment.”
The technology not only adds great value in that you are able to start the production in shorter time, but it also provides a greater reservoir contact, which improves the stimulation of the well, according to the company.
An animation of the i-Frac system in action is available.
Contact the author, Scott Weeden, at firstname.lastname@example.org.