35 OCTOBER 2022 WorldWide Drilling Resource® Geothermal Drilling by Ronald B. Peterson Drilling Products Specialist, Mountainland Supply Company Geothermal drilling can involve both deep hot hole geothermal usually used for power generation and the shallower cooler geothermal resource used in the ground source heat pump (GSHP) industry. Deep hot hole geothermal is interesting and challenging. Ideally, bottom hole temperatures up to 300°F (148ºC) and even in excess of 400°F (204ºC) are encountered. If no water is encountered, it is considered hot dry rock; and to be of any value, water has to be injected, which will then flash over to steam and provide energy for a potential power plant. These holes can be in excess of 10,000 feet in depth. When water is present, it will manifest itself as high pressure steam. It will usually be difficult to control and requires you to have a drilling program designed to provide the necessary equipment and operation procedures to provide the necessary control. Hydrogen sulfide gas is often encountered. This is a very poisonous, corrosive, hazardous gas. Drilling operations and the drilling fluid must be designed to compensate for the control of this gas. The geothermal drilling most frequently encountered is for the GSHP industry. It simply uses the natural temperature differentiation of the subsurface of the earth to augment heating and air conditioning operations to lower the overall cost of maintaining a desired temperature in our inside environments. Typically, these boreholes are shallow and completed in the unstable surface formations. The hole is drilled, then a designed heat loop is installed, and the hole is grouted with a grout designed to maximize heat exchange with the surrounding formations. The heat loops can be somewhat fragile, so the hole has to be open and stable to place them, and for them to work effectively. Since the holes are usually shallow, the drill rig often has a much smaller footprint for easier maneuverability and greater efficiency. Drilling fluids used are usually simpler, but need to be monitored and maintained to ensure performance. Typically, water, soda ash, bentonite, and polymers are selected and used at the appropriate concentration. In any drilling operation, it is always a good idea to get with your drilling fluids provider and have them get with their vendor representative to ensure you are using the correct products at the correct concentrations to maximize the effectiveness of your drilling operation, minimize your overall costs, reduce the cost to your customer, and maximize your profit. Thanks for reading. As I often say, “A man has to know his limitations.” Working together, it is amazing where we can go. Enjoy the trip! If you have any questions on drilling fluids or if you have another topic you would like addressed, please remember this column is ours, help me make it of value to you. It needs to be an interactive tool and I need your feedback. Please send your suggestions to Michele (below) and she will get them to me. Ron Ron Peterson may be contacted via e-mail to michele@worldwidedrillingresource.com GEO This is just a sneak peek ~ visit www.worldwidedrillingresource.com/gallery.html for more photos online! Wyo-Ben was very busy. Mr. McCool was on hand in the Geothermal Supply Co. booth. Well-Vu was out in force. Mike represented Cotey Chemical Corp. Hole Products was well-represented by a great group. Kade and Blake were ready to talk Total Dynamic Hoists. Jim was on-hand at Mudslayer. Michelle & Todd with Infinity Tool Mfg. My wife and I are both petroleum engineers. She is a third generation oil and gas person. We both read your magazine every single month. There are so many columnists who are really terrific writers. Last month's [July 2022] article by Tim Connor "Work," was one of the BEST EVER. It expressed exactly the way Ann and I feel about working in the oil and gas business. Despite its many ups and downs, we never want to retire. Thank you for your great magazine. Best of luck to all of you. Bill Daily Santa Fe, NM
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