Trending Now: Cemented Liners in The Bakken

The use of cemented liners in the Williston Basin has improved production for several operators. Even as the practice has the potential to become an industry standard, technology providers are already working to enhance the completion approach.
By Luke Geiver | April 22, 2014

The use of cemented liners in the Williston Basin has improved production for several operators.  For Whiting Petroleum Corp. and Fidelity Exploration & Production Co., the completion methodology has proven to be so effective, that each has planned nearly every future well in 2014 around the completion approach. During the DUG Bakken and Niobrara Conference held earlier this year in Denver, Francisco Fragachan, director of sales and marketing for Weatherford’s pressure pumping division, spoke to a large crowd about the evolution of completion practices in the Bakken. “There are opportunities for improving our completion effectiveness versus efficiency,” he explained.

Production increase summaries from both Whiting and Fidelity show just how effective the use of cemented liners can be. Kent Wells, president and CEO of Fidelity, a subsidiary of MDU Resources Group, gave analysts an update on the exploration and production company’s Williston Basin assets in early March, revealing the impact of cemented liners. According to Wells, a Three Forks well completed in Mountrail County, N.D., the Purcell 3-4-33H, was completed using a cemented liner. The well produced a 46 percent increase over 140 days when compared to a well completed during the same time, in the same area, using a different completion approach.

Whiting has gone exclusively to the cemented liner approach based on IP rates that have increased from 30 to 100 percent over wells completed in similar geologic areas with different completion methods.
“A lot of the industry is headed this way,” said Wells.

The Case for Cement
Cemented liners are not a fad. Although Adam Anderson, vice president of the western U.S. for Baker Hughes, says that the industry still knows very little about the shale formations such as the Bakken, Niobrara or Eagle Ford, “the prevailing wisdom is shifting towards more frack effectiveness.” In other words, he told the DUG crowd at the panel discussion featuring Fragachan, that today’s goal is in “breaking more rock,” a process that will yield substantial returns.

The concept of the cemented liner seems simple, and the basic premise is that it does break more rock. Cement is pumped on the outside of the well bore’s liner. In an open hole design, there is nothing around the outside of the liner, so when the rock surrounding the liner is perforated, the perforations go through the casing directly in the rock in random directions. However, the subsequent frack will follow the path of least resistance. In a cemented lateral, the perforations pass through a layer of cement first, which acts as a directional conduit, allowing the completions team to place perforations in a specific area along the segmented fracture zone. Knowing where the fractures are going, in essence, allows the teams to justify placing more fractures per zone. 

Dustin Gentry, completions account manager at Trican Completion Solutions, is well-versed in every completion approach on the market, specifically those geared towards the use of cemented liners. The concept of the cemented liner versus an open hole design is simple logic, he says. “The cemented liner gives the operator a lot more control of where they are directing the frack. These shale’s will not produce as much naturally if you don’t frack it correctly,” Gentry says.

The ability to precisely place a fracture along an interval zone is allowing operators the luxury of breaking more rock. Most using the method are perforating an interval between four to ten times, Gentry says. “Before, it was only one set of perforations per interval, but now with the ability to know where your frack generally is, an operator can put more fracks into an interval along several more contact points within the interval.”

The method involves the use of wireline which is used to set the bridge plug and activate the perforation gun. The plug is pumped into the hole where it bridges off a section of the well, followed by the use of the perforation gun to perforate the surrounding well bore region. “Plug-and-perf is kind of king right now because that is what everybody is comfortable with,” Gentry says. In the Bakken, that wasn’t always the case, however.

Anderson says Baker Hughes is one of many companies that have undergone a frack sleeve and plug-and-pert technology evolution. In the Bakken’s early days, the play lent itself to sliding sleeves because operators were taking advantage of natural fractures in the rock. Combined with an open hole design, the fracture sleeves were installed between isolation packers that could swell and isolate individual sections of the well bore. Balls could then be pumped into the well bore to activate, and open individual fracture sleeves and the sleeve’s accompanying ports. The ball’s seat themselves into specifically sized ball seats in the sleeves and force the sleeve to move, which opens the ports. With the swell packers isolating each sleeve from the next, the fluid pumped into the wellbore along with the ball is diverted through the ports and into the rock formation. The process drastically reduces the amount of downhole time needed to complete a well and can help to finish a completion job in much less time than the plug-and-perf method.

Sliding sleeves also involve downhole assembly tools that could move a single fracture sleeve along the well bore with the use of coiled tubing, allowing an operator to perform multiple fractures without bringing the downhole equipment out of the well. According to Anderson, one of the main reasons for the use of sleeves in the Bakken’s early days was directly related to the pumping horsepower capacity in the play. Today, there is more pumping horsepower than ever before, he says, and multiwell pads are making the benefits of the quicker sleeves less obvious. “People are thinking about applying more contact points,” he says.

Gentry and his team from Trican claim to offer operators the best of both worlds: the pressure pumping efficiency of using frack sleeves combined with the multiple fracture initiation points that you would get with a plug-and-perf strategy. If they can deliever, the new ball drop activated multistage frack system designed for cemented liner applications will play a more prominent role in the way Bakken wells are completed during the era of cemented liners.

Cemented Liners 2.0
By now, the use of cemented liners is becoming an undeniable trend. The practice is drastically increasing production for operators who use the approach correctly. But, just as operators are starting to adopt the completion method for great production yields, energy services companies are already making the method more effective. According to Gentry, the completion approach can still achieve greater production benefits, all in shorter time. Warren Miller, marketing manager at Trican, helped a recent Bakken operator complete 21 fracture stages in a single day. A typical plug-and-perf team can perform roughly four to six fracture stages per day, he says.

Gentry and Miller are working to educate completion engineers and operators about the i-Frac CEM system. Trican developed the ball drop activated system for cemented liners. The company has used the system on more than 190 wells. The system is installed as an integrated part of the lower completion string. Each fracture stage, depending on the length determined for the fracture zones, can contain one to 20 sliding sleeves. After a toe initiation device is activated, a single ball can be pumped into each fracture zone (which may contain up to 20 sleeves). The single ball will open all of the sleeves in the specific fracture zone, one-by-one.

Once the balls reach the sleeves, the pressure causes the seats to expand, activating the sleeves, before the ball moves onto the next sleeve seat. “In the past, sleeve systems weren’t able to offer multiple fracture initiation points with just one ball. One ball could only open up one sleeve at a time. We can open up multiple sleeves with a single ball,” Gentry says. For an example, he says that on a 10-stage job, eight sleeves could be placed in each fracture zone. To open each of the sleeves in each of the zones, only 10 balls would be needed, but 80 fracture initiation points could be stimulated.

To deploy the i-Frac CEM system, the Trican team needs to know the pumping pressure the completion team plans to use, and the specific locations for the fracture stimulations desired by the geologists. “You can align the placement of your frack port with the logs that show the highest level of hydrocarbon saturation, the highest level of natural fracture capabilities or the highest levels of porosity,” Miller says.

Trican uses pumping data during the completion to determine if each of the sleeve ports is opened. Each port will only open when certain pumping pressure and continuous flow rates are achieved, so based on the data that summarizes the pressure and flow, the team can verify if a port has been opened or not. Pumping pressure required for the system ranges from 10,000 to 15,000 Psi depending on the inner diameter of the horizontal casing string.

“People wonder how we know if all the sleeves were opened,” Gentry says. “We tell them you can only push so many barrels through so many holes. We look at the pressure spike signatures as the ball opens each sleeve in a stage individually. We compare the downhole pressures we are seeing along with the pressure pumping rates at surface and if you get to your maximum planned pumping rates, then all sleeves were opened in that stage.”

The beauty of Trican’s cemented liner-based, multi-fracture system is not just about the ability of the system to provide multiple fracture initiation points along the discrete zones by utilizing the presence of the cement conduit. It is also about speed. “We are talking minutes versus hours,” Miller says of the system. Because the process uses continuous pumping, there is not stoppage time to pump-down and pull-out wireline or stop to perform pump maintenance. The number of balls dropped is also significantly less than most ball drop systems. And the system can use dissolving balls, which eliminates the need to drill or mill out the balls before production can start.

The approach allows Trican to use the ball drop method during zipper fracks as well, reducing the time needed to complete the wells for the operators, and the time the Trican team has to be on the well site. The time saving aspect of the approach allows Gentry's customers to potentially save several hundred thousand dollars per well and move field personnel and equipment off a well in two days instead of five. “You can get 40 to 50 stages fracked per day on a well pad. That is what this technology has done,” Gentry says.

Trican’s excitement for its ball drop cemented liner system is justified. The company owns the patent to the system that Gentry says is the most mechanically sound on the market. There are, however, other major companies that are coming out with a similar system, he says. Although both Gentry and Miller believe in the Trican system, they are extremely certain that operators such as Whiting and Fidelity are examples of what the future of completions in the Bakken will look like. “I don’t know where the studies are on it [cemented liners], but the technology we have and the proven production increases from using it, say yes,” Miller says, “this is the thing to do.”

Author: Luke Geiver
Managing Editor, The Bakken magazine