Industry Article: Offshore Technology Aims at Lowering Breakeven Economies

From cost-effective RSS to lower vibration underreamers service companies are designing tools to meet industry demand.

Publication: Hart Energy Playbook
Publication Date: 12/01/2017

by Scott Weeden, contributing editor

Cutter block for underreamer reduces vibration

If there is a limitation to underreamers, it is the cutting structure or what that structure does to the entire BHA. Underreaming operations can be notorious for having high levels of vibration. That is one of the things Schlumberger wanted to address with its StingBlock advanced stabilization conical element cutter block along with providing a cutting structure that increases overall durability and allowing it to last longer and drill faster.

The StingBlock cutter is essentially the cutting structure of the Schlumberger Rhino integrated borehole system. There are a few key features that are used on the StingBlock cutter to better stabilize the BHA and improve the overall cutting structure durability. The underreamer has the company’s proprietary staged profile, which helps to better distribute the cutter loads and to stabilize the overall cutting structure element, explained Wiley Long, product champion for StingBlock cutter for Schlumberger.

Offshore Technology Aims at Lowering Breakeven Economies

The StingBlock cutter block is the industry’s first geometry cutter block that features a stage gauge pad design and Stinger conical diamond elements.

“You can imagine it as multiple gauge pads as you go up the cutting structure. Increasing that gauge pad area helps smooth out vibrations during underreaming operations. Our experience shows that the majority of damage that occurs on the reamer cutter structure is due to impact damage. For the cutting structure we’ve taken a page out of our bits playbook and incorporated the Stinger conical diamond element. The Stinger conical element has a much superior impact resistance than a conventional PDC cutter,” he said.

In a conventional underreaming-while-drilling BHA, the assembly is susceptible to vibration because of the great distance between the two cutting structures drilling simultaneously—the underreamer is typically about 150 ft from the bit. Because of the distance, quite often the tools will be drilling in different kinds of rock, which can generate a lot of vibration into the drillstring, he explained.

What helps reduce vibration are the staged pads that better stabilize the cutting structure. It provides more contact area for the cutting block and the extra level of stability that is needed.

The rows of PDC cutters on its conventional reamers are symmetrical. “Symmetry might sound nice but in things with moving parts it can be susceptible to harmonic vibration levels. With StingBlock cutter we’re creating an alignment with PDC cutters and Stinger elements more broadly distributed across the width,” he noted.

Schlumberger devised a different system that would incorporate two Rhino StingBlock reamers into the same BHA. It is called the Rhino RHE rathole elimination system. “For that system you have your top Rhino reamer in the conventional location above the LWD tool. Your second Rhino reamer would be just above the RSS about 20 ft to 25 ft from the bit,” he continued.

The top reamer would be used while drilling the majority of the interval. Once the bit reaches total depth the upper reamer is deactivated, and the lower reamer is activated. “We can then underream that 120 ft plus of rathole and eliminate an additional trip to underream that rathole,” he added.

In the MWD and LWD tools there are sensors measuring vibration. In lab tests and field operations the company found the ability of StingBlock cutter to reduce vibration levels.

“We’ve had several runs in the GoM and offshore Brazil. The first one we had in the GoM was with our 11625 Series of StingBlock cutters. That one was underreaming a pilot hole from 12-1/4-in. to 14-1/2-in. Immediately on back-to-back runs the customer saw an increase of footage of 97% compared to the offset runs and a 32% increase in ROP,” he said.

RSS designed for ERD wells

Operators are looking for cost-effective ways to drill faster and longer laterals since the more footage that they can expose, the higher the level of returns, said Juan Restrepo, product champion for RSS for Schlumberger.

“When you measure drilling efficiency, it can be seen in two ways—drilling faster and minimizing the number of BHAs used to drill to the objective. All the development we have had in recent years has to do with how to have the system provide a quality hole for our client in the shortest period of time,” he continued.

There are three points that have to be hit to reach new levels of performance—drill faster, the ability to drill longer wellbores in the target zone and provide high quality holes. “No matter how far you drill, if you don’t have a hole that can be used, it is going to be a waste of time and money for the whole well construction and production process,” he added.

Schlumberger has added two new members to its PowerDrive RSS family. The PowerDrive Xcel RSS is focused on offshore and ultra-extended-reach-drilling (ERD) wells, while the PowerDrive Orbit RSS is focused on land operations, including super laterals.

“The ERD wells are getting longer and longer, so downhole automation is becoming more critical for the consistent performance of directional tools, since building micro-tortuosities across the extended lengths reduces the amount of energy required for the actual drilling process,” Restrepo explained.

Offshore Technology Aims at Lowering Breakeven Economies

The PowerDrive Xcel RSS was designed for use in high-profile directional drilling operations. It provides inertial directional control in deviated sections—a feature that can be toggled on and off by a downlink.

Each RSS has a distinctive design, but both the PowerDrive Orbit RSS and the PowerDrive Xcel RSS build on their direction and inclination sensors close-to-the-bit, to provide automated closed- loops simultaneously on inclination and azimuth. Closing this loop downhole, allows customers to automatically hold any 3-D orientation vertically and laterally for a given target, minimizing the interaction from the surface in the drilling process for faster penetration rates.

“There are no more commands to be sent to the tool. The tool is going to measure its orientation downhole and do exactly what it needs to keep the target set,” he said. That takes the human out of the equation.

At 350 revolutions per minute, the tool can still measure downhole both inclination and azimuth. “One of the quests we had [in the design] was to accurately measure the inclination and azimuth dynamically to confidently let the tool decide for itself what to do without requirements from the surface. That is a very important point of this,” he emphasized.

Vibration affects where energy is going in the drillstring. “For drilling performance characterization of the vibration patterns is critical. Both technologies provide triaxial measurement of both shocks and vibration,” Restrepo continued.

The PowerDrive Xcel RSS also was shown to be effective in open-hole and cased-hole sidetracks due to the inclusion of a gyro and a customizable bend offset. The tool can measure rotation and stick-and-slip in magnetic interference environments. It also maintains directional control through the zone of exclusion, he added.

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