Pipe dope ... facts and fiction
One of the last things that you think about when preparing for any drilling job is grease, but in reality, it should be one of the first. Inadequate lubrication can result in lost time, as well as money on a drilling rig. Using the wrong compound can also be as costly.
Today’s business requires us to drill faster, deeper, and especially in the HDD market pull longer runs than ever before. There is little time between job locations to make repairs, much less service equipment properly. All this begins to take a toll on rigs, bits, pipe and tooling. And with the escalating price of drill pipe, it only makes good sense to invest a little time to become familiar with not only the industry-standard copper-based products, but the new non-metallic compounds as well. How do you know what is right for both your equipment and for that unique jobsite? Are all compounds basically the same? Are they really necessary? What is currently required by the jurisdictions in your area?
Selecting the right drill thread compound is now more important than ever before. We are faced with environmental issues that we would not imagine as little as three or four years ago. Things have changed significantly in pipe drilling compounds in the past couple of years. The grease that our fathers and grandfathers used contained additives, such as lead, zinc, molybdenum, just to name a few. All would certainly raise a few eyebrows if used today. Commonly used compounds in today’s markets are copper based and the new metal free.
However, all changes come with issues. Copper is not as “slick” as the lead and zinc-based compounds resulting in different frictional and torque issues. Copper compounds also had an early tendency to wash off the drill stem pipe with high pH muds. And copper flake would, in rare cases, clog the atomizer nozzles on HDD automatic lube machines. All of these problems have been resolved as manufacturers have improved, redesigned and reformulated compounds.
The primary purpose of a thread compound is to provide a barrier that will separate the two pieces of work by introducing a layer of dissimilar material. Without this layer, the threaded surfaces of the drill pipe and coupling can “weld” together under the heat caused by make-up and/ or torsional stress down-hole. Typically, “welding” or galling is more prominent on newer connections because the surfaces have not been work-hardened. A new drill string or individual pipe will appear to have a mirror finish and be smooth to the touch, but in reality, is jagged and pitted when observed under a microscope. Thread compounds fill in the pits and cover the uneven areas by using a grease carrier which contains solid metallic and non-metallic fillers. They may also contain other additives such as extreme pressure, anti-rust, anti-wear, and high temperature.
One of the main issues is initial make-up torque. All connections will continue to experience down hole rotational torque to some extent. But inadequate torque on initial make-up can result in rolling or wobbling of the couplings causing damage to the entire string. This is the most common cause of pitting, galling and break-out issues in all types of drilling operations. Premium thread compounds are designed with a special blend of solids, engineered to provide a coefficient of friction that actually increases with makeup. This increasing frictional property will reduce the tendency for down-hole makeup in severe drilling applications such as geothermal, high angle holes and deep horizontal bores.
Proper and adequate application of the thread compound is also an issue, especially with HDD rigs. Larger pipe requires more of the compound to be applied than smaller pipe. That may sound simple, but in most cases, the hydraulic “automatic” applicators simply do not apply enough product. This is especially important with the new metal free compounds. Improper amounts of compound can cause more damage than under-torque.
Selection of the proper drill pipe compound is just as important as selecting the right bit. Key points to consider are the environmental conditions of the bore where certain metals are undesirable, size of the drill pipe, and anticipated temperatures. Remember, all thread compounds are not created equal. Discount manufacturers do not have full-scale base grease manufacturing and blending facilities and lack test facilities needed to ensure a quality finished drill compound. Axle grease is for wheels, not drill pipe.
As our grandfathers so eloquently said, “You always get what you pay for.” Invest in the time to get the “right” drill compound. Your investment will pay great dividends for years to come.
Michael Melancon is the national sales manager, Water Well and Horizontal Directional Drilling Products Division, for Jet-Lube, Inc.