It can be said that the drill pipe on an HDD project are like a person’s bones in the body. When a person wants to take care of their bones and make them last for a good lifetime — or long project in this analogy — they take care of their bones. A smart person eats a well-balanced diet with the right minerals and vitamins and tries to keep hydrated so bones and joints stay lubricated and last a long time. When they do have trauma or stress, they go to the doctor for X-rays and examinations. This way the smart person helps his bones last 70 years or more.
A smart driller can learn from this concept and pick the right pipe for the work he is going to perform and then maintain it for longer service life of the pipe.
Selecting Proper Drill Pipe for Your Need
A person should consider many things when purchasing maxi rig drill pipe: (1) Strength, which is the relationship of Tube Diameter, Wall Thickness and Grade of steel; (2) Torsional Stiffness, which becomes more important on longer bores to avoid “pipe wrap;” (3) Connection size and type, with consideration of O.D. and I.D. for downhole hydraulics, as well as strength and serviceability; (4) Value, with consideration of New vs. Used pipe and some definition of how to determine the value or anticipated life and risk of Used pipe; (5) Quality and understanding the benefits of advanced manufacturing procedures; and (6) Hard Banding, with consideration of your project needs.
(1) Strength: Let’s establish that HDD contractors use Grade S-135 (135,000 psi minimum yield strength) drill pipe because of its strength, and also because of the “toughness.” Modern chemistries of steel used by major drill pipe manufacturers have taken this to a higher standard. The new blends of steel allow for heat treating that makes the pipe “tougher” than found in previous years.
(2) Torsional Stiffness. This becomes very important while drilling a pilot hole on an extended reach HDD project. For example, 6-5/8 in., 27.70#/ft., S-135 drill pipe that has a .362-in. wall thickness will have 59 percent less “twist” than 5 in., 19.50#/ft., S-135 that also has a .362-in. wall thickness. This becomes very important while trying to maintain “high side” or the clock-face position of the mud motor and drill bit at the end of a 5,000-ft string of pipe.
(3) Connections. Most HDD contractors prefer to use common, field-tested, API style connections such as 4-1/2 -in. IF, 5-1/2 in. Full Hole or 6-5/8 in. Full Hole. These connections are available in their standard form, or with a “double shoulder” feature. The double shoulder versions of these connections provide a secondary shoulder at the end of the pin. This adds approximately 30 percent more strength to the connection and helps prevent over-torque to the connection if “slip torque” is experienced downhole.
(4) Value. Do you want to buy new or used drill pipe? The primary thing to consider is the useful remaining life of used pipe compared to new. For example, let’s evaluate 6-5/8-in. full hole connections on 6-5/8 in., 27.70#/ft. S-135 tubes. This pipe is typically built with 8-1/2-in. O.D. tool joints. The minimum O.D. for this pipe to pass a premium class or DS1-CAT5 inspection is 8-in. O.D. New pipe is available for $XX.XX per foot; therefore, you can calculate the value that you are willing to pay for used pipe based on the remaining useful life before the pipe falls below premium class inspection criteria. Another important consideration while determining the value of used pipe is the “useable tong space.” This same 6-5/8-in. pipe is typically manufactured with 10-in. pin tong length and 13-in. box tong length. Some of the tong space may be lost to hard banding if it is placed in the traditional area since you cannot grip hard banding with the rig vises or jaw dies. It is important to look at the useable tong length of pin and box tool joints when considering buying used pipe.
(5) Quality (of New pipe). Consider the manufacturers quality control standards, quality of steel “source” (manufacturer and/or processor), as well as chemistry (high molybdenum, low sulfur and phosphorous) and length of upset from the manufacturer. Request the exacting standards of API spec 5DP, qualified to API Q1 and ISO 9001 from the manufacturer and/or processor. The length and quality of the internal upset transition between the tool joint and the mid-body tube will help prevent bending and rotating fatigue to help avoid downhole failures. Learn about or look at the internal upset at the end of the tube where it meets the tool joint.
(6) Hard Banding. This can extend the life of drill pipe when used on rock crossings. Consult with your vendor about the placement and types of hard banding that are available. Some manufacturers or suppliers can recommend different types of hard banding, as well as the placement of the hard banding for HDD projects (special features).
Proper Drill Pipe Maintenance and Inspection
A good drill pipe maintenance program is vital to the long life of your new drill string. That starts with removing the shipping/storage compound that is on the box and pin ends when you get your new pipe string. This should be followed by an initial “make and break” procedure to get the connections started off right. Always apply the recommended joint compound with every use and spread it around the entire tread face equally, not just a dollop here and let the make-up turns spread it around. Also try to instill on the guys in the field that the plastic thread protector caps are not a one-time shipping item to be thrown away. Put the caps back on at the end of each crossing. They are called “thread protectors” for a reason.
Schedule your drill pipe for inspection at regular intervals and/or after a really tough project. T.H. Hill has published inspection criteria that has become an industry standard for inspection of used drill pipe. Your drill pipe vendor or manufacturer should be able to provide reference material, calculations or inspection reports to help you determine which pipe is right for your application.
If you take care of your drill pipe like some people take care of their bones, then it can last you a lifetime.
Grady Bell is with J.T. Miller LLC.