Tagging wells saves time, money and the environment

RFID technology does more than unlock doors or gain admission to ski lifts

BY ALAN BAILEY FOR GREENING OF OIL

In perhaps its most visible form, radio frequency identification, or RFID, has become familiar to many as the magic badge that you wave in the air to unlock an office door, open a security gate or perhaps gain admission to a ski lift. But, behind the scenes in many industries, RFID has become something of an ubiquitous technology, widely used to track freight and perform many of the functions of a traditional bar-coding system.

Marathon Oil Corp., working with various industry partners, has been spearheading efforts to apply RFID technology in the drilling of oil and gas wells, to cut costs and save time by more efficiently controlling the drilling equipment deep underground in a well bore, Tim Deines, Marathon’s well performance manager for upstream technology, told Greening of Oil. And improved efficiency translates to a reduced environmental impact, thanks to less time spent running the engines that power the drilling rigs; less need to “trip,” or pull, the drill pipe from a well; and less need to vent gas when completing natural gas wells, Deines said.

Marathon’s industry partners in its RFID initiative include Weatherford International, a company with expertise in downhole electronics, and Petrowell, a U.K. company that specializes in downhole equipment design, including RFID tools, said Phil Snider, Marathon’s senior technical consultant for upstream technology.

Micro-electronics

In essence, an RFID application has a micro-electronic radio receiver that acts as a code reader, to control some device, say an office building door lock. An RFID tag, placed in proximity to the reader and consisting of a tiny radio transmitter/receiver in the form of a micro-electronic chip, is activated by signals transmitted by the reader device, then responds by sending a coded signal back to the reader. If the reader receives the appropriate code, it activates the required operation, such as the unlocking of the office door.

There are several ways in which this type of technology could be applied when drilling an oil or gas well. However, Marathon’s main focus is on fitting RFID readers into downhole well equipment and then using RFID tags to pass instructions to the equipment: In the same way that an RFID security badge will open an office door, an RFID tag passed down a well will activate a piece of equipment, shut it down or perhaps open or close a valve. Marathon is investigating the operation in this manner of as many as 30 types of downhole tools, Snider said.

Tiny tags

A typical RFID tag used in a downhole operation is about 3 millimeters in diameter and about 3 centimeters long.

“It’s just a very small computer chip that’s embedded in a cylindrical piece of glass, and we’ll either pump it down to the downhole tool that we’re trying to actuate, or we’ll gravity drop it,” Snider said.

When pumped down a well, tags are injected through a small side port in the drill pipe into the drilling fluid, typically drilling mud, that circulates through the well. The drillers program the tags for whatever operation the subsurface equipment needs to perform, and typically send several identically programmed tags down the well, to ensure that at least one tag triggers the required action.

“Most of the tags read a lot better if they’re parallel to the reader,” Snider said.

Lab testing has indicated a 99.9 percent successful read rate with just a handful of tags, he said.

Pre-planning

Some pre-planning is needed — given the time that it takes for the tags to pass down the well, the drillers need to inject the tags into the well ahead of the precise time at which the downhole well operation needs to take place.

And the tags and RFID readers have to be constructed in a way that protects the micro-electronics from pressures of perhaps 15,000 to 20,000 pounds per square inch in the lower reaches of a well, while also withstanding the mechanical jostling within the well.

“One of the bigger challenges that we’ve had is that a lot of these tools are being used in a drilling environment, so the pipe is turning … there’s a lot of downhole shock and vibration,” Snider said.

And although there are alternative technologies for controlling downhole equipment, such as sending signals in the form of pressure pulses through the drilling mud, the RFID technique enjoys the advantage that multiple tags can simultaneously control multiple items of equipment, each with a unique RFID code, while not interfering with the mud pulsing techniques that are typically used in applications such as making continuous downhole measurements while drilling.

In addition, the RFID tags can sometimes simply be dropped down the well, or used in situations where some well fluid other than drilling mud is being used.

Multiple perforations

In one of the first of its applications of RFID techniques, Marathon used RFID tags to fire perforating guns when stimulating multiple gas-bearing zones in the complex reservoir of a gas field on Alaska’s Kenai Peninsula.

“We’re building out with this RFID a bunch of ways to do multizone stimulations,” Deines said. “In that case we can stimulate all the zones in the well in one day, without having to flow back the well or do any other well operation.”

This new way of executing a well completion avoids the need to vent any gas from the well, and enables the well to go straight on line for gas sales, he said. The multizone stimulation technique forms part of Marathon’s Excape® Completion Process technology, used by the company to complete gas wells in Alaska’s Cook Inlet basin and to complete the horizontal wells that produce gas from tight shale-gas reservoirs. Shale-gas plays have become a key part of the company’s exploration and development portfolio in the Lower 48, Deines said.

In Alaska alone, Marathon has saved 150 million cubic feet of otherwise vented gas by using multizone stimulations, Deines said. The company has received a U.S. Environmental Protection Agency natural gas STAR award for the Excape technology, he said.

Underreamers

Marathon has been testing the use of the RFID technology to control underreamers, devices used to widen a well bore below a narrower section of pipe.

Underreamers wear out quite rapidly when in use, causing the drillers to pull the drill pipe and the tool from the well to install a new tool for continuing the operation. But with an RFID system, the drillers can run perhaps three underreamers down the well simultaneously, with each of the tools controlled by a unique RFID code. As each tool wears out, RFID tags can shut that tool down and start up a new one, thus eliminating the need to pull the drill pipe from the well.

And that’s a really big deal in some of the areas that companies like Marathon now operate.

For example, Marathon has major interests in the deepwater oil and gas regions of the Gulf of Mexico and Indonesia, where drilling now takes place in water depths of around 8,000 feet and is moving into depths of 10,000 to 12,000 feet, with drilling rig operational costs running at about $1 million per day, Deines said.

Millions of dollars

In these deepwater situations, avoiding the need to pull the drill pipe from a well, thanks to RFID-controlled underreamers, could save major dollars in drilling costs per tool-change operation, Snider said. And keeping the drill pipe in the hole reduces the operational risks for the drillers, while also avoiding damage to the well bore.

RFID techniques can also reduce costs in downhole pipe retrieval operations by enabling the tag-triggered disconnection of a section of downhole drill pipe from the tools at the bottom of the well, in a situation where perhaps the bottom section of the drill string has become stuck.

“We think a drilling disconnect, where we’re circulating a chip down and disconnecting from the tools, could save us easily half a day or maybe even a whole day, by the time we mobilize equipment,” Deines said. “Just a single activation by a chip in the deepwater environment we believe could save us anywhere from $1 million to $3 million, each time we use the technology.”

In another application, Marathon has been partnering with drilling fluid firm M-I Swaco to use RFID technology to control a device called a circulating sub that enables drillers to circulate fluids in a well above the drill bit, to clean the well bore, for example. With the RFID-controlled equipment in place in the well, tags dropped into the well can cause the port on a circulating sub to open or close, while other appropriately coded tags can control a barrier valve within the well bore, Snider said. It’s also possible to instruct the downhole equipment to perform an operation at a specific time, he said.

And it’s even possible to run multiple circulating subs in a single drill string, with each device controlled by an individual RFID code.

Field trials

So, given the benefits that RFID technology can bring to drilling operations, how far have Marathon and its business partners progressed in bringing the technology into regular use?

“We are field trialing the prototype tools, just ahead of full-blown commercialization,” Snider said.

Those field trials are on the increase and have been taking place in the North Sea and North Dakota, in addition to the initial use of the technology in Alaska. The idea is to test the technology in safe situations, where wells are already being drilled, before going to full-blown commerciality, Snider said.

And the use of RFID technology is but one example of how state-of-the art electronics, computer systems and materials science are transforming the modern oil field, greatly improving efficiency, improving safety and reducing environmental impacts, he said.

Links of interest

Petrowell

Marathon Oil Corp.

Contact Alan Bailey through publisher@greeningofoil.com