Scott Weeden looks at new developments in extended reach drilling, which include managing vibrations, thereby allowing the BHA and bit to stay on bottom longer and get the well to total depth.
The slip-on Python Polymer Rotating drilling centralizers/stabilizers are installed on drillpipe. The tools provide up to 60% wear reduction, torque and drag reduction and less stick/slip and associated vibration. Photo from TDTECH. Centralizer Distributors
Extended reach drilling (ERD) is not about a new piece of technology. Sometimes the operator and service provider have to focus on some of the simplest equipment—cement plugs, centralizers, stabilizers and drillpipe—to ensure success.
The benefits can be far reaching. The current world record for an extended reach well is set at 44,291ft (total measured depth), drilled by ExxonMobil, extending from onshore Sakhalin Island in eastern Russia out into the Sea of Okhotsk. This has helped the supermajor reduce the number of offshore facilities it has had to construct at Sakhalin to two.
“Operators are now drilling to 44,000ft quicker than we used to drill the 26,000ft wells,” says Iain Hutchison, managing director at Scotland-based Merlin ERD.
Achieving such feats is about education. Hutchison points to Chevron’s MAXDRILL and ExxonMobil’s Fast Drill programs as examples of significant pushes in educating drill crews on how to avoid drilling problems and drive continuous improvement. According to ExxonMobil, its drilling rate has improved more than 80% since introducing the Fast Drill process. In fact, ExxonMobil has drilled more than 80% of the top 50 longest ERD wells.
“Let people understand what it takes to drill these wells,” Hutchison says. “Often the skills and intelligence of the people on the rigs aren’t being fully utilized. We’re not showing them why these wells are different. They’re coming from drilling less challenging deviated wells, or sometimes vertical wells, to suddenly drilling complex, high-angle wells, and wondering why they’re getting stuck,” he adds.
Merlin, which is an ERD and ultra-long lateral (ULL) engineering consultancy, supports its engineering work with a three-day operations course with instructions that are objective, enabling the rig hands to have the knowledge they need.
“The human factor is an absolute key. We’ve seen time and time again when some of the best programs and engineering fail because the office hasn’t made it clear to the guys on the rig what is different about this well or explained why the instructions are written [a certain] way,” Hutchison explains.
The company builds on a basis of engineering, fundamentals and physics, adding some local conditions or problematic formations for the outline of the course. After the first half-day, the rig hands all start contributing and discussing problems as well as successes.
While drilling a 44,000ft well, if something goes wrong at 27,000ft, it will have major cost and operational implications. “We focus on where the problem could occur, to avoid it. About 80% of the problems tend to be procedural or human factors,” Hutchison says.
Planning and execution are critical
The Reelwell Drilling Method is a closed-loop drilling system that uses a dual drillstring. The annulus between the dual drillstring and the wellbore remains static and is free of drill cuttings.Image from Reelwell.
Big data is also used in both the planning and execution of an ERD well, according to Halliburton. Today, every bit of data can be used and analyzed automatically in real-time and then used to benchmark future operations.
“The industry, through specialized software packages, has the capability to do automatic classification of rig activity with very high accuracy and definition,” says Wael El Deftar, Sperry Drilling chief global advisor, at Halliburton. “We can start to benchmark our performance on every single activity from the moment the well is spudded until the moment it reaches total depth. Over time, we can start to identify and quantify where we are spending too much time for no reason (hidden non-productive time).
“We can start doing performance comparisons well-to-well, rig-to-rig, crew-to-crew and field-to-field. We can standardize performance by capturing the areas where we are excelling and supporting the crew’s efforts. We also find the areas to reduce inefficiency,” he explains.
Halliburton does a comprehensive risk analysis method as one of its approaches. The company analyzes the data and finds what types of problems will be faced during the ERD well execution. “We start to put measures into the design to overcome this risk in case it materializes. We call this approach the Global Drilling Risk Factor Method. It allows us to be prepared for contingencies,” he continues. “Even if we run into trouble, we don’t have to spend much time on this problem because we have the contingency plans available. That’s how we can improve performance.”
The company has a worldwide engineering group called the Drilling Engineering Solutions Group to deal with challenges such as ERD project planning.
This industry noseplot shows the record ERD wells worldwide. Image from Merlin ERD Ltd.
While new technology is always a great attraction, getting more out of existing technology or even using it correctly also has huge value, Hutchison says. “We frequently come across opportunities that can be delivered with a bit of clever engineering, rather than a costly rig upgrade, which was perceived to be ‘essential.’”
One example of using an older technology correctly is pumping cement plugs. “When a well is drilled, cement plugs are pumped. It’s very simple. But, have most operators pumped a cement plug to 30,000ft? It was good for wells at 15-16,000ft, but now the plugs are being pumped twice as far. It’s little things like that,” he adds.
However, the newest developments are in the area of vibration management. “If you avoid vibration, generally the bit will hold up,” Hutchison says. “When you download the report and see what has been happening with the vibration, you realize that the bottomhole tools don’t fail; we beat them to death.
With ERD operators have drilled over 40,000ft offshore from a land drilling location. ExxonMobil’s ERD has used the technology to reduce the need for offshore platforms. Image from Merlin ERD Ltd.
“We’re almost to the point where we can run vibration sensors all the way along the drillstring,” he continues. “Then you can see the different harmonics if you have vibration. It explains strange wear patterns and why we’ve damaged the bit. If you don’t have your BHA (bottomhole assembly) stabilized and the bit face is vibrating, it drills an over-gauge hole, and you don’t have the same directional control.”
TDTECH, a New Zealand company, has the next generation of stabilizers and centralizers, according to Hutchison. The company offers mold-on drilling stabilizers and casing centralizers that are less expensive because these are simpler than previous mold-on centralizers.
“Previous polymer casing centralizers were slip-on type while polymer drilling stabilizers used a combination of materials, including steel, aluminum and fasteners to hold the tools in place. Our tools are a single piece, rather benign, high-grade polymer with zero metal parts,” says Geoff Murray, general manager, TDTECH.
Its Archimedes Screw pumping effect helps reduce equivalent circulating density (ECD). Drillstring rotation revolves the screw elements, thereby pumping the drilling mud and reducing ECD. Another means for reducing ECD is via better hole cleaning, wherein less cuttings in the hole equate to less pressure drop, Murray explains.
Its Python Polymer Rotating drilling centralizer/stabilizer provides 60% to 95% wear reduction along with more than 50% torque and drag reduction, which might enable use of smaller drillpipe. The wear reduction results of the slippery, fiber-reinforced polymer exhibits a fraction of the abrasive wear of metal-on-metal contact, he continues. It also reduces stick/slip and associated vibration.
The Switchblade profile and monoblade orientation reduce torque, drag and torsional vibration.Photo from ED Projects.
Hutchison also mentions a different kind of stabilizer called a Switchblade from ED Projects in the Netherlands. “They’ve got this Switchblade stabilizer that helps the vibration like any stabilizer, but it’s got a really peculiar blade set. A huge issue is that stabilizers get balled up in the shallower, softer formations. This stabilizer, with its hydrodynamic design with enhanced flow-by area, can help if there is a clay-balling problem,” he says. The hydrodynamic design also helps with tripping by tackling the root cause of pack off, which minimizes wall cake damage when both tripping and backreaming.
According to ED Projects, better drilling fluid displacement reduces the risk of swabbing and surging, which are key causes of wellbore instability. The tool profile and monoblade orientation reduces torque, drag and torsional vibration, which are key causes of borehole enlargement and subsequent BHA component failure.
There are also improvements in tractor technology and intelligent completions, Hutchison notes. “It is often not the drilling; it is the completion or the well service that is the problem. Drilling is the easy part.” The really clever solution is how you complete the well, and then how you service the completion if you have a problem.
Companies are doing everything they can to lower drillpipe weight. There are two approaches to this. The lubricity of the drilling fluid is one approach, but there are only small gains to be made using drilling fluids. The second approach is using lighter tubulars.
“If the tubulars weigh less, you have less reactive torque. A real advance is aluminum drillpipe in the high-angle section. However, one of the challenges with aluminum drillpipe is the connections, which are generally made of steel. The body is quite soft so it wears. The TDTECH mold-on centralizers can be attached to the aluminum drillpipe to reduce the wear,” he explains.
Another technology undergoing development is the Reelwell drilling method (RDM). A trial was performed as part of a joint industry project on ERD wells (called ERD 20km+) by Norwegian company Reelwell, supported by The Research Council of Norway, operators Total, Petrobras and DEA, and Halliburton.
Bow Spring Centralizer For Wellbore The RDM is a closed-loop drilling system using a dual drillstring. Clean drilling fluid flows down its annulus while mud and cuttings return to the surface through the inner string. The hole is free of cuttings, and the drilling technique reduces torque and drag while enabling wellbores beyond conventional reach.