17 MAY 2022 WorldWide Drilling Resource® HDD Diversity by Ronald B. Peterson Drilling Products Specialist, Mountainland Supply Company This month’s discussion topic is “HDD (Horizontal Directional Drilling) Diversity.” Horizontal Directional Drilling is advancing a hole that is, as the name indicates, horizontal. It is usually very shallow, and is very carefully monitored to make sure it is on target. The fluid properties and the testing procedures are similar in horizontal drilling and vertical drilling. Calcium or hardness and pH still need to be identified, measured, and controlled at desirable levels; calcium preferably below 200 ppm (parts per million), and pH between 8.5 and 9.5. Filtrate or water loss and filter cake are also still critical properties. The test procedures are basically the same, but some of the desired properties are different. Select a good, reliable, convenient source of makeup water, test it, and treat it as necessary. To get the desirable properties, add soda ash to adjust the calcium content and raise the pH as necessary. You will need a bentonite product designed to provide the correct properties for horizontal boring and polymers to achieve desirable filtration control properties and to stabilize active formation clays and shales. You may also need a lost circulation control material in very fragile formations. Viscosity is a measurement of the apparent thickness of the fluid or resistance to flow and can be a necessary evil. Higher viscosities require greater pressures to move the fluid and can cause frac-outs in the formation, creating potential environmental and cosmetic concerns. The viscosity is not an indication of carrying capacity of the fluid. You need to suspend and carry the cuttings by building different properties related to viscosity. These properties are yield point and gel strength. Different bentonite products are designed to develop different drilling fluid properties; thus, they are designed for different drilling disciplines. Some provide high viscosities and others enhance the yield point and gels. Some polymers will give you a great deal of viscosity, but only a couple of them will give you yield point. Viscosity is resistance to flow, and you are trying to maintain flow. You are usually boring very close to the surface and so the ground is very fragile. High-viscosity fluid plus high solids content results in reduced flowability. Reduced flowability means more pressure will be required to move the slurry. High viscosity causes high circulating pressures. High circulating pressures tend to break things and cause frac-outs and/or humps in streets, highways, and driveways. This is never good. Suspension is critical in HDD; any solids generated need to be kept in suspension while in the borehole so they do not settle out and close off the bore. Gels are the tendency of the fluid to set up when idle. They need be able to be broken so the fluid can flow again when disturbed. This ability is referred to as fragile gels. els, yield point, and viscosity - while related properties - are not the same. A thick fluid may not suspend cuttings, but a thin fluid can be designed to suspend cuttings. In HDD, flowability is the major concern. When you select your drilling fluid additives, make sure they provide the properties you need to successfully complete the bore and install the product. There is a popular statement: “At the end of the bore, if the fluid will flow, the product will go.” If you have any questions on horizontal directional drilling fluids or if you have another topic you would like addressed, please remember this column is yours and needs to be an interactive tool. Please contact Michele (below) and she will get your question to me. Ron Ron Peterson may be contacted via e-mail to michele@worldwidedrillingresource.com DIR For more information call: (270) 786-3010 or visit us online: www.geothermalsupply.com All New! Atlantis-Pro Vault • Traffic-Rated Capable • Simple installation • Trouble-free operation
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