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Rotary Steerable System proves effective on HDD project.

Working with InterSyn Technologies, InterCon Construction teamed up with Schlumberger Drilling and Measurements to complete the first HDD (Hard Disk Drive) See hard disk and HDD caddy.

HDD - hard disk drive
 crossing using a Rotary Steerable System A rotary steerable system is a new form of drilling technology used in directional drilling. It employs the use of specialized downhole equipment to replace conventional directional tools such as mud motors.  (RSS (Really Simple Syndication) A syndication format that was developed by Netscape in 1999 and became very popular for aggregating updates to blogs and the news sites. RSS has also stood for "Rich Site Summary" and "RDF Site Summary. ) in the bottom hole assembly. Although a 1.300-foot run isn't the challenging crossing an HDD contractor would normally choose to apply the Schlumberger PowerDrive RSS, it offered an ideal opportunity to explore the benefits of drilling with the system while learning what's different compared to drilling rock with a mud motor. Each company learned from the other during the drill and are ready to tackle a longer crossing ideally suited to rotary steerable technology.

The right project

Both InterCon and Schlumberger wanted to use the PowerDrive on a relative short crossing in a rock formation to critique the tool's performance. Each company knew that differences between oilfield conventions and the HDD industry would crop up and need to be dealt with. Despite the obstacles, InterCon's directional drilling Directional drilling (sometimes known as slant drilling outside the oil industry) is the science of drilling non-vertical wells. Directional drilling can be broken down into three main groups: Oilfield Directional Drilling, Utility Installation Directional Drilling (commonly  management team made up of Bruce Gabrielse and Steve Allen were looking forward to using the tool to complete challenging HDD crossings.

Panhandle Energy's Cass County Cass County is the name of nine counties in the United States:
  • Cass County, Illinois
  • Cass County, Indiana
  • Cass County, Iowa
  • Cass County, Michigan
  • Cass County, Minnesota
  • Cass County, Missouri
  • Cass County, Nebraska
  • Cass County, North Dakota
, MO, 1,300-foot crossing of two small creeks and a county road proved to be the perfect choice. InterCon called Schlumberger's HDD representative, InterSyn Technologies to mobilize tools and support personnel from Schlumberger's Oklahoma City Oklahoma City (1990 pop. 444,719), state capital, and seat of Oklahoma co., central Okla., on the North Canadian River; inc. 1890. The state's largest city, it is an important livestock market, a wholesale, distribution, industrial, and financial center, and a farm  US Land PowerDrive Service Center Center and incorporated Mi HDD's expertise in fluid engineering and products for their support.

Rotating makes the difference

Conventionally, a downhole motor with a bend to control toolface has been used to drill rock formations on HDD crossings. In order to steer, the motor has to slide with the drillstring not rotating. The torque generated by the bit and the drag generated by the drillstring result in toolface fluctuations and reduced weight on the bit.

On the other hand, rotary steerable systems are able to make changes in inclination and azimuth azimuth (ăz`əməth), in astronomy, one coordinate in the altazimuth coordinate system. It is the angular distance of a body measured westward along the celestial horizon from the observer's south point.  while the drillstring rotates continuously. They can produce a cleaner, straighter borehole bore·hole  
A hole that is drilled into the earth, as in exploratory well drilling or in building construction.
 while reducing drag, improving the transfer of weight to the bit and increasing the rate of penetration. The unique feature of Schlumberger's Rotary Steerable System--PowerDrive--is that all external parts of the tool rotate, and no stationary parts are touching the borehole. Continuous rotation combined with the absence of annular annular /an·nu·lar/ (an´u-ler) ring-shaped.

Shaped like or forming a ring.


 bottlenecks significantly reduces the chance of cuttings buildup, packing off and getting stuck.

To date, the practical upper limit of HDD drills has been about 6,000 to 7,000 feet. PowerDrive Rotary steerable tools have been used in the oil and gas industry to drill horizontal displacements in excess of 30,000 feet.

One tool--many options

The PowerDrive tool utilizes mud flow in both the control and bias sections to enable the tool to steer or drill straight. First, mud flows through turbines in the control section of the tool producing the electrical power for the guidance electronics and control valve A device that modulates the flow of fluid in a conduit in response to a signal from a process measurement control system.  positioning. The control valve directs a small portion of the mud flow in the bias section to one of three steering pads located just behind the bit. These pads extend and push against the formation in the direction opposite the intended path to produce side cutting force and steer the drill string. The simple design, utilizing only mud power, with no downhole hydraulic pumps or electrical motors, can inherently improve reliability.

The steering settings of the tool can easily be reset without tripping out of the hole by varying the mud flow through the tool. It can also be set in one of two modes. When in steering mode, the pads extend according to according to
1. As stated or indicated by; on the authority of: according to historians.

2. In keeping with: according to instructions.

 the programmed toolface and more or less frequently according to the amount of steering force the driller wants. Toolface and steering force can be adjusted to direct the tool along the intended path and counteract walking tendencies in the formation.

The tool can also be programmed for "inclination hold." Using its own inclinometers located 7 feet behind the bit; the tool adjusts steering pad movement automatically to hold the drill path at the current inclination. This feature is very useful for drilling tangents in formations that have strong build or drop tendencies. The target inclination can be adjusted in 1/2 degree increments and left or right steer can also be applied and adjusted while in inclination hold mode.

Lessons learned

Both InterCon and Schlumberger agreed that this crossing was going to require a lot of communication. Discussing all options for each situation allowed everyone involved to learn and develop confidence in the tool's capabilities for directional crossings. InterCon's veteran drilling supervisor Don Masters made sure everyone involved knew that production would be secondary to learning from each other and ensuring that InterCon delivered a quality crossing to their customer.

Schlumberger drilling engineers provided a hydraulic study to InterCon indicating that the mud system would need to provide 1,200 psi at a 450 gpm flow rate to complete the 9 7/8-inch pilot bore while maintaining the 6 3/4-inch tool's steering force. This was asking the American Augers DD-330 rig for all of its pump's capacity, but InterCon's Allen was confident the rig could deliver. Approximately 200 feet into the drill, it was noted that the tool was not responding to commands.

It was decided to pull out of the hole and review the tool's on-board diagnostics On-Board Diagnostics, or OBD, in an automotive context, is a generic term referring to a vehicle's self-diagnostic and reporting capability. OBD systems give the vehicle owner or a repair technician access to state of health information for various vehicle sub-systems.  to determine exactly what mud flows and communications the tool was receiving. Because the tool uses mud flow for its power and communication, the flow meters and pressure gauges on the rig need to be accurate.

The review indicated that the rig's flow meters were not indicating the true drill-stem flow and the tool was not recognizing the downlinks to change the steering settings due to this discrepancy.

Armed with accurate information on the mud flow, Schlumberger's PowerDrive engineer came up with the flows needed to properly communicate to the tool. The PowerDrive went back into the borehole and there were no more problems downlinking to the tool for the remainder of the job.

When needed, the tool delivered 1.5 degree builds per joint (4.8 degree/100 foot DogLeg dog·leg  
a. Something that has a sharp bend, especially a road or route that bends abruptly.

b. A sharp bend or turn: Make a dogleg at the fire station and continue south.
 Severity) using only 80 percent of its steering force. This short crossing had little to no tangent on the bottom, so a moderate build was held from the end of the entry tangent to the start of the exit tangent. The tool was drilling on line and building predictably at the planned 1 degree per joint to the point the survey tool read 103 degree inclination which indicated 104 degrees at the bit. The formation also exhibited a slight tendency to the right. At this point, a downlink was sent to the tool, placing it in inclination hold with 15 percent left steer. The final seven joints were drilled with the borehole holding a steady 104 degrees and exiting less than a foot from the planned exit point.

Mi HDD ran the Drilplex HDD system throughout the pilot hole with a special 2 percent lost circulation material additive called MIXII to combat the fractured rock zones without plugging the internal PowerDrive flow paths, thus ensuring power and communication stayed intact. While maintaining constant returns and providing excellent penetration rates with optimum cutting transport the system proved a perfect match for the PowerDrive and geology.

InterCon's surveyor, Pat Unwin, felt that in addition to being able to steer while rotating, "the inclination hold feature makes PowerDrive a very useful tool in the HDD industry."

InterCon's Masters concurs. "We're excited to explore how this tool works and learn how we can apply it on future jobs. Being able to steer while rotating is going to open up a whole new range of projects where HDD was previously considered impossible or where the risk and expense of two intersecting bores was required."


Rotary steering tool: InterSyn, (262) 352-4639, or circle #185

Utility contractor: InterCon, (608) 227-7473, or circle #186

Bryan Wichmann, InterSyn Technology, Houston, TX
COPYRIGHT 2005 Oildom Publishing Company of Texas, Inc.
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Title Annotation:First Look
Author:Wichmann, Bryan
Publication:Underground Construction
Date:Sep 1, 2005
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