MudCube Offers Breakthrough in Drilling Fluids Technology
A breakthrough in traditional shaker technology has resulted in a new system for treating drilling fluids that can meet more stringent health, safety, environmental and work requirements, according to officials with Sandnes, Norway-based Cubility A/S.
The MudCube solids control system uses vacuum conveyer belt technology to separate solid wastes from drilling fluids, rather than the mechanical vibration that has been used since the 1930s, said Asbjorn Kroken, vice president of engineering, sales and marketing for Cubility, in an interview with Rigzone, noting that the MudCube represents a ‘significant breakthrough’ in shaker technology.
Unlike traditional systems, the MudCube is a closed, integrated system for solids control and mud treatment, Kroken said. The negative pressure created by the vacuum doesn’t allow oil and gas to escape, ensuring that gases and vapors are transported within the system to a safe area on the rig.
The closed system can meet the latest health, safety and environmental (HSE) standards by reducing risk that workers face from exposure to hazardous gas, skin contact with drilling fluids, noise and vibration from machines, Kroken said.
“When it comes to the system itself, it’s more efficient to use negative pressure and a belt to transport solids versus vibration,” said Kroken. Through this method, 90 percent of the fluid is separated out from solids, generating less waste, allowing for lower costs in terms of transportation and in manhours.
Utilizing the MudCube can minimize the environmental impact of drilling by reducing drilling waste and minimizing carbon dioxide discharge. Other advantages include optimized drilling performance by maintaining low-gravity solids (LGS) at low concentrations without high rates of dilution and reducing circulating temperatures.
“High concentrations of LGS can also create unwanted downhole condition which can reduce the overall drilling performance. This could be issues as extra circulation to clean the hole for solids, higher risk of stuck drillpipe, or lower rate of penetration,” said Kroken.
Besides HSE benefits, MudCude’s other main benefit is the substantially lower fluid content in the drilling waste, up to 90 percent less fluid than with shakers. The company estimates that the MudCube can reduce waste volume by up to 50 percent and dilution by up to 40 percent. Screen costs also can be reduced by up to 65 percent and manhours by up to 30 percent.
Using the MudCube also can reduce costs for operators by allowing more fluids to be recycled, reduce mud cost with cuttings, overall rig weight and the need for cuttings dryers. The MudCube improves the filtration, allowing less low gravity solids to be ‘recycled’ into the drilling mud. This requires less new base-mud to be added to keep the fluid parameters as per specifications, especially mud weight.
“A stable mud weight will contribute positively to maximize the planned rate of penetration, but it has to be noted that there are many other factors as type of bit and downhole motor that contributes more to higher rate of penetration part than the mud weight,” Kroken said.
A typical 3-deck shaker weighs around three metric tons compared to 1 tons for the MudCube. Once screen panel weighs around 10 kg and a 3-deck have 16 panels giving a total of 353 pounds (160 kg) per shaker compared to the seven pounds (3 kg) for a MudCube screen.
A lightweight MudCube system will reduce cost - and in most cases smaller footprint - for new builds where MudCube is an integrated part of the initial rig design. For upgrades on existing rigs, MudCube will replace not only shakers but also some of the auxiliary equipment as centrifuges.
“The average retention time of cuttings spend on the revolving screen is around five seconds compared to 30 seconds on a traditional system,” Kroken said. “This means that the MudCube system can process a higher volume per hour than shaker as wells as filtrating more efficient because the screen is cleaned during each revolution.”
The MudCube system, which consists of MudCube units, vacuum skid with cyclones and pumps with silencers, and a control system. The system can operate without high g-forces, degradation of cuttings and fluid vapor pollution associated with conventional technology.
The system, which can be controlled and operated remotely through camera, sensors and a control system, enables operators to go from water to oil based fluids, which hold several advantages compared with water-based fluids, including better performance.
Development of the MudCube has been underway since 2004. The MudCube’s benefits were proven when three MudCubes were installed In October 2012 on board the jackup Maersk Giant (350’ ILC), which is under contract to drill for several operators on the Norwegian Continental Shelf until this year’s fourth quarter. Cubility noted that the MudCube received positive feedback from workers on board the Maersk Giant, from a reduction to noise and fumes and cleaner working areas due to less frequent removal and cleaning of shaker screens to consistent mud-weight and no need to add premix.
Statoil, which designated the MudCube a proven technology in 2012 and has played a vital role in the MudCube’s development with financial and technical support, conducted detailed testing for Maersk Drilling, Talisman Energy and Dong E&P Norge AS, who partly funded the equipment and installation. Testing occurred during the drilling of the 16/10-5 Isbjorn and 3/7-8-S Trym Sor wells.
Cubliity also has a facility in Norway where testing is conducted. In the facility, which consists of a traditional shaker and one with a MudCube system and tanks, pipes, heaters, pumps, control room and accessories -- different types of solids, such as shale or clay, can be added to simulate actual offshore operations.
Currently, 50 MudCubes have or are set for installation on drilling rigs. Last fall, the company announced a distribution partnership with TWI Oilfield Services. While the partnership agreement is still in place, its implementation date has been postponed temporarily due to the company wanting to use the MudCube putting a project on hold. A date has not yet been set, but Kroken remains confident that the agreement’s implementation will move forward soon.
Cubility also is working with other U.S. companies to the use of the MudCube in U.S. onshore shale plays. The company has previously conducted a trial for Chevron Corp., ConocoPhillips Co. and Royal Dutch Shell Plc in the Marcellus shale play. The company currently is not active in the Marcellus due to low gas prices.
The MudCube was initially tested on offshore Norway on drilling rigs, but operators drilling in U.S. shale plays can benefit from the technology as well due to its HSE benefits, the amount of mud associated with shale wells that will need to be recycled, and to increasing calls for regulations to require closed loop drilling systems in some U.S. states, Kroken noted.
North Dakota has now prohibited so-called open pits were they dump fluid and cuttings and have to convert to ‘closed loop systems’. This mean that is an advantage to separate out as much as fluid as possible as all waste has to be shipped to be storage/discharge location. “The allowed regulatory concentration of oil and chemicals in the drilling waste is also being lowered as in Colorado, Wyoming, Pennsylvania and New York,” said Kroken.
The company recently signed an agreement with Samsung Heavy Industries to install 12 MudCubes on two of Statoil’s Category J harsh environment jackups in the North Sea. Up to 24 MudCubes could be installed if this project is expanded, Cubility said in a statement. The first six MudCubes are scheduled for delivery in this year’s fourth quarter; the remainder of the MudCubes would be delivered and installed on the rigs every four months thereafter.
The company also has designed and installed a system for Saipem’s Scarabeo 5 (mid-water semisub). The rig, currently under contract to Statoil, is set to drill offshore Norway. Cubility also has deployed another MudCube to Brazil, marking another milestone for the company, Kroken said.
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