Lighter, More Intelligent Drill Strings Beckoning
by F. Jay Schempf
|Saturday, November 15, 2003
The drilling industry's multifaceted quest for downhole tools made of lighter materials, along with ways to make those tools react both quicker and smarter, is picking up momentum.
Analysis: A number of pilot-stage initiatives are aimed at developing new components used in the drilling process that should bring producers closer--more quickly--to the ultimate goal of creating totally "smart" wells. Two such projects in particular stand out from the crowd. One is centered on lightweight, tough composite drill pipe and the other at steel drill pipe that returns subsurface data measurements on an almost instantaneous, "realtime" basis.
Except for rough estimates of depth drilled and a few other parameters, measurements of crucial downhole conditions have historically been conducted as separate operations that called for stopping the drilling and pulling the entire drill string from the hole. Then, either the bottomhole assembly was altered by adding new tools, or separate tools were lowered into the hole, usually on wireline. In any case, drilling was paused, often for long periods, leaving the operator to pay for expensive rig downtime.
Over the past decade or so, however, downhole drilling tools of many types have been designed to "phone home" from underground, allowing the drill string to remain in the hole while the phone calls are fielded. The advent of such tools revolutionized the industry, allowing operators to conduct a number of measurement-while-drilling (MWD) and logging-while-drilling (LWD) operations. Most of these tools in some way alter pressure in the drilling fluid, and sensors at the surface read the fluid pressure changes as binary codes. But since the number of quality drilling fluid pulses are limited, and take time to be transmitted up the hole and then processed, the actual readings are delayed. Such delays often result in imprecise drilling and/or inaccurate geological information, which many times result in productivity losses costing millions of dollars, particularly in deep offshore wells. Human lives, too, also can be threatened if warnings from downhole are overtaken by the actual dangerous conditions they detect.
So, as deeper wells have been drilled to more reactive formations and in more hostile environments, the desire for more accurate, faster downhole measurements has become a major industry goal.
Ongoing research and development in search of various new drilling sequence components is varied and spread among a number of different entities, including both public and private institutions. However, the general inertia appears to be forward and positive. Two such initiatives stand out.
Just last month, results from joint government-industry testing of lightweight, composite drill pipe advanced toward provision of an important new tool for recovering more oil and gas at a lower cost from both vertical and directional wells.
The Department of Energy's National Energy Technology Laboratory (NETL) said the composite drill pipe--developed by Los Angeles-based Advanced Composite Products and Technology Inc. (ACPT)--was tested successfully in a Le Flore County, OK, horizontal gas well during the summer. An existing vertical well was reentered and kicked off vertically at a depth of about 1,400 feet. According to NETL, not only did the carbon fiber pipe perform well in a hard and highly abrasive formation, but the test also included use of air-hammer drilling techniques that severely challenged the pipe's fatigue life, mechanical strength, and ability to deal with stress. A long horizontal section was drilled during a week's time. However, when the drill string was pulled from the well and examined, the composite pipe showed little or no signs of wear, say DOE officials.
A more detailed description of the overall composite pipe project is available in a January 21, 2003 story in RigZone by oil and gas analyst Richard Mason, titled "Composite Fiber Drill Pipe Adds New Twist to Directional Drilling."
The pipe itself is being developed under a $2.82-million, five-year contract with DOE's Office of Fossil Energy. Briefly, the flexible pipe is manufactured by winding graphite fibers and epoxy resin around a supporting spindle. The composite tube is cured, and the spindle then removed. After the pipe is machined to fit borehole tolerances, it is coated to resist abrasion.
The composite pipe is much lighter and more flexible than steel drill pipe, say NETL officials. This is particularly important in permitting producers to reenter old wells and drill horizontally to reach untapped oil and gas formations, they said, adding that steel-based drill pipe can suffer fatigue cracking and rapid wear when flexed continually during a horizontal drilling operation. And while the price of the composite tubulars currently is about three times that of steel drill pipe, researchers are working on reducing costs. Meanwhile, project designers plan additional tests in the coming months aimed at helping to convince the industry of the applicability of composite drill pipe under actual field conditions.
DOE officials also point out that the carbon fiber make-up of the new pipe also could be a major step toward developing future "smart" drilling systems. Research to come will include embedding wire conductors in larger, 7-inch composite drill pipe to carry data from the bottom of the hole to the surface while drilling is underway. With a digital communications capability, such systems could give operators realtime data for monitoring drilling progress, for avoiding undue stresses on the drill pipe itself, and for making virtually instant decisions to pinpoint the well's target formation.
For more information, contact David J. Anna, NETL at email@example.com (412-386-4646).
Another "smart" drill pipe initiative--one much further along than the composite pipe project--is the ongoing development of steel drill pipe that incorporates high-speed downhole communications (telemetry) in the pipe itself. The system, whose development started as part of a joint government-industry project in the late 1990s, was spun off as a separate project and is now being marketed by the companies who developed it as IntelliPipe(r). The companies involved are Novatek Inc. of Provo, UT, and Grant Prideco, Houston, who in early 2000 formed a separate company, IntelliServ Inc., to commercialize the system.
Basically, IntelliServ's core technology is a unique, noncontacting coupler embedded in the connections at each end of 30-foot sections of drill pipe. When connected, multiple drill pipe sections close a passive communications link. This link, known as IntelliCom(tm), involves a ring-shaped transducer in each end of the pipe (tool joint) that sends data to the next pipe section without direct electrical contact. An armored data cable runs the entire length of each drill pipe section, completing the data path between the IntelliCom links.
Because they need not touch, the noncontacting transducers can be embedded and protected within the drill string components, thereby avoiding the shorting, corrosion, and other damage common to conventional electrical connections, which must touch in order to conduct data signals across the mated surfaces of the tool joints.
IntelliServ says the IntelliPipe system can interconnect many devices and systems to improve drilling productivity. With it, the company says, information can be moved between various members of the drilling assembly much like several users on a computer network or Internet can share information.
The technology is useful in all types of threaded drill string assemblies, including reamers, jars, stabilizers, and other subs. It also can be used in devices that have rotating joints through which a data signal must pass, from a downhole motor and bit at the bottom of the string to a "data swivel" at the top, where the high-speed data is stripped and sent to surface monitors. Additionally, the same data can be sent to a server for broadcast to anywhere in the world via the internet.
The premier application of the IntelliServ network is for high-speed seismic characterization of a reservoir during drilling. Other applications, using addressable "nodes" along the drill string, include realtime feedback and control for various downhole steering, LWD, modeling, and monitoring tools. Data transmission rates have approached 2 million bits/second, which are multiple orders of magnitude faster than existing mud-pulse data transmission systems.
The system has been field tested at both Novatek's 1,000-foot test well in Utah and at the Gas Technology Institute's 2,000-foot well test site at Catoosa, OK. Full-scale tests have included multiple make-ups (50 to 150 pipe sections) to full torque on several joint pairs. Additional tests, conducted at the DOE's Rocky Mountain Testing Center near Casper, WY, involved 121 joints of drill pipe, drill collars, and various subs for a total drill string length of 4,531 feet, with an average data rate of 2 megabits/second.
IntelliServ literature says a number of field demonstrations are planned before commercial introduction of the new system. The company is seeking opportunities for such field tests, and notes that such a test will have a "fairly benign" effect on normal drilling operations since it will consist largely of handling drill pipe.
For more information, contact John Rogers at firstname.lastname@example.org or (304-285-4880), or David R. Hall at email@example.com
Now, all either of these two products need is just one company who's willing to have a "go" with a drill pipe string marked: Serial No. 1.