NOV’s low thermal conductivity internal pipe coating and two-stage mud chiller extend BHA service life and reduce NPT.
MICHAEL ADAMS, REZA FARD, MARK CANLAS, LUTHER GRESSETT and JESSICA STUMP, NOV
Drilling fluids (or mud) serve as the first line of defense in maintaining wellbore stability and protecting downhole equipment. They cool and lubricate the drill bit, remove cuttings and clean the hole. As operators drill deeper wells and longer laterals in areas such as the Eagle Ford, Haynesville, Utica, and Marcellus shale plays, they encounter extreme downhole temperatures that often exceed the operating limits of bottomhole assembly (BHA) components, including sensitive electronic sensors and elastomer materials.
Most BHA equipment, such as drilling motors and MWD/LWD tools, is rated to 300°F (149°C), but formations increasingly exceed 350°F (177°C). These elevated temperatures transfer considerable heat into the drilling fluid, degrading its properties. Thermal breakdown accelerates corrosion, erosion and material fatigue in downhole equipment, leading to higher non-productive time (NPT), increased drilling fluid and maintenance costs and greater risk of equipment failure.
NOV has developed an integrated approach to managing high-temperature drilling operations. This approach combines TK™-Drakōn—a novel, low thermal conductivity internal coating—with the Tundra™ Max mud chiller, which reduces drilling fluid temperatures at the surface. Together, these technologies help keep downhole equipment cool, enhance safety, improve reliability and increase overall drilling efficiency.
KEEPING FLUIDS COOL DOWNHOLE
For more than 80 years, NOV’s Tuboscope™ business unit has developed protective coatings that extend the service life of tubulars by protecting against corrosion, wear and deposit buildup, while also improving hydraulic efficiency. Following requests from both oil and gas and geothermal operators for an insulating coating, the company’s R&D team focused on thermal conductivity. TK-Drakōn builds on this legacy by blending expertise in oilfield pipe coating technology with advancements in materials science to set a new industry standard, Fig. 1.
THERMAL CONDUCTIVITY
Thermal conductivity is a measure of a material’s ability to conduct heat. For coated drill pipe in high-temperature drilling applications, the lower the thermal conductivity, the better. Lower thermal conductivity translates to lower heat transfer rates through the drillstring, keeping the drilling fluid cooler to minimize the temperature impact on BHA tools, thus extending their operating life.
Carbon steel, one of the most common drill pipe materials, has a high level of thermal conductivity (45 W/mK), which rapidly transfers heat from the formation to the drilling fluid. Instead of initiating a research project to find different material for drill pipe that provides the desired thermal conductivity, the focus shifted to developing an insulating coating material for carbon steel, with a thermal conductivity of 0.5 W/mK or lower. This new coating must match the corrosion resistance and hydraulic efficiency of legacy coatings, while being applied at minimal thickness to enhance insulation, corrosion control, and deposit resistance.
NOV Tuboscope researchers developed and tested different coating formulations for their thermal conductivity, using a heat flow meter that followed the ASTM-E1530-19 standard, the primary measure of thermal resistance/conductivity for solids (-4°F–590°F, or -20°C–310°C). They compared each formulation to the measured k value of the current Tuboscope™ drill pipe coatings, which had not been altered for insulation performance.
While the current coating portfolio had an average thermal conductivity of 0.8369 W/mK, it was still higher than the target value. After iterative formulation adjustments, the company developed a coating formulation with an average conductivity of 0.1620 W/mK—more than five times lower than the existing coatings and nearly 280 times lower than steel.
CORROSION, ABRASION AND IMPACT RESISTANCE
Chemical and performance testing were performed using autoclave and immersion methods. Autoclave tests were used to evaluate coating performance under elevated temperature and pressure in both sweet (CO2) and sour (H2S) environments. Immersion tests involved prolonged exposure to various corrosive solutions at high temperatures, using clear reaction vessels to observe material degradation over time.
Physical property tests included:
Taber abrasion testing to measure coating loss (in mils or microns)
Direct and reverse impact resistance testing
Flexibility testing using ring crush and mandrel bend methods.
The surface roughness of the applied coating was also measured to confirm that it maintained the desired level of hydraulic efficiency and ensured steady fluid flow through the pipe.
TK-Drakōn demonstrated superior chemical, abrasion and impact resistance, along with excellent corrosion mitigation properties, verifying its robustness in rigorous high-temperature drilling environments. The new insulated coating delivered these results at an applied thickness of just 20–30 mils (thousandths of an inch).
The coating applies smoothly and evenly to minimize surface roughness and increase hydraulic efficiencies, which reduces fuel consumption. A smooth coating helps prevent the buildup of scale and other solid deposits while promoting the laminar flow of drilling fluids in the pipe, Fig. 2. This optimizes mud pumping efficiencies at the surface and provides additional cooling benefits to the BHA.
With more than 1.0 MMft of TK-Drakōn-coated pipe in service, NOV is enabling operators to access deeper, hotter and more complex targets. Although insulation alone isn’t enough, starting with cooled mud is critical.
MUD COOLING EQUIPMENT AT THE SURFACE
Once the heated drilling fluid returns to the surface and flows through the shale shaker and other solids control equipment, it enters a mud cooling system before being pumped back downhole. The three primary types of mud cooling equipment are evaporative, air blast and chillers.
An evaporative mud cooler uses water as the cooling medium, spraying it over coils that carry hot drilling fluid. As the water evaporates, it draws heat away from the fluid. However, evaporative coolers have notable limitations: efficiency drops significantly in high ambient temperatures or elevated humidity, where heat transfer is less effective in already hot, moisture-laden environments. They also require a continuous, high-volume water supply, typically sourced from nearby bodies of water or through regular water truck deliveries.
Air blast coolers use air as the primary cooling medium. Fans draw air through fins connected to a tube heat exchanger that carries the fluid. This method extracts heat from the fluid via air flow. Just like evaporative systems, hot environments hinder their cooling capacity. However, air blast coolers do not require large volumes of water, making them suitable for regions where water is scarce, such as the Middle East.
Chillers use an HVAC refrigeration system—similar to the A/C in a car or residence—to extract heat. Chillers, unlike coolers, have the unique ability of precise temperature control. They are designed to continue cooling in high ambient temperatures and do not require an external water source.
TWO-STAGE, CLOSED-LOOP MUD CHILLER
NOV’s Tundra™ Max mud chiller integrates both air blast and chiller technologies into a two-stage, closed-loop configuration, Fig. 3. The chiller handles oil-based mud (OBM), synthetic-based mud (SBM) and water-based mud (WBM) and does not require an external water source.
The first stage uses an air cooling unit, while the second stage utilizes a refrigeration unit. Both stages use a plate and frame heat exchanger. Each plate and frame heat exchanger consists of alternating plates that carry either drilling fluid or cooling fluid. These are set up in a counterflow configuration, where drilling fluid flows in one direction while the cooling fluid flows in the opposite. This proven design exposes more of the heated fluid to the cooling medium—a water loop cooled by both the air blast and chiller stages—enhancing heat transfer efficiency.
The plates themselves feature a corrugated herringbone pattern, which induces turbulence in the fluid as it passes through. This turbulence increases the surface contact between the fluid and the plates, further optimizing the heat transfer process from the drilling fluid.
At the wellsite, the single-skid, trailer-mounted chiller is set up in parallel with the active mud system. The Tundra Max draws fluid from the suction tank, typically the cleanest point in the surface system after solids removal by the shakers. This fluid is then chilled and reintroduced into the solids control tank, which usually contains the hottest fluid in the cycle. The design effectively forms a heat sink, continuously reducing the overall temperature of the mud system.
The result is a closed-loop cooling process that naturally distributes lower temperatures across the fluid cycle before it is recirculated downhole. This method allows cooler mud to reach farther into the wellbore, enabling operators to extend the service life of BHA equipment, reduce downtime and enhance overall drilling performance.
CASE STUDY
In South Texas, a major operator faced extreme bottomhole temperatures during long lateral drilling in the Eagle Ford shale. Cooling became increasingly difficult in lateral sections extending beyond 20,000 ft (6,096 m), restricting the use of critical downhole tools. In offset wells, temperatures reached 385°F (196°C), presenting a significant risk to the integrity of downhole tools, electronics and mud properties.
To counter the potential of these challenges, the operator deployed NOV’s integrated temperature control solution. At the surface, the Tundra Max achieved an average temperature drop of 53°F (29.5°C), from 143°F (61.7°C) inlet to 90°F (32.2°C) outlet, Fig. 4. This cooling improved the quality of fluid circulated downhole, helping create a more stable drilling environment.
When used alone, the mud chiller helped reduce bottomhole temperatures to approximately 366°F (186°C). However, when paired with the TK-Drakōn thermally coated drill pipe, bottomhole temperatures dropped even further, to an average of 318°F (159°C). This combination not only preserved the performance of expensive downhole electronics but also enabled tools to operate closer to their maximum rated lifespans, including critical batteries and sensors for automated drilling and formation evaluation.
In addition to extending tool life, the integrated solution enhanced fluid rheology control, reducing reliance on costly chemical additives to compensate for heat-related breakdown. The improved thermal consistency minimized risk at the surface, enhancing safety by lowering wellsite personnel’s exposure to hot fluid returns.
The synergy between surface cooling and thermally coated drill pipe enabled the operator to avoid tool-related trips, maintain higher rates of penetration (ROP), and reduce overall NPT. These performance gains will translate into faster, more efficient wells with lowered operational risk, helping the operator meet its project goals on time and under budget.
CONCLUSION
Temperature management has become a critical enabler for safe, efficient drilling in rigorous environments. As lateral lengths push toward 5 mi, and well designs grow increasingly intricate, integrated cooling solutions that maintain fluid temperatures within the pipe and down to the drill bit need to provide clear operational advantages, both downhole and at the surface.
Field data from South Texas demonstrate that the integrated approach extends tool life, improves fluid integrity, and enables higher ROP while reducing NPT. This capability reflects NOV’s commitment to delivering solutions that meet the demands of modern high-temperature drilling environments, enabling operators to drill farther, faster and safer without compromising reliability or cost control. WO
REFERENCES
Fard, R., “Low thermal conductivity coating extends BHA life and improves drillstring performance in challenging high-temperature environments,” presented at the SPE/IADC International Drilling Conference, Stavanger, Norway, March 4-6, 2025.
Pandurangan, P. and I. De La Cruz, I., “Two-stage mud chiller thermohydraulic model development and validation, presented at the SPE/IADC Middle East Drilling Technology Conference, Abu Dhabi, UAE, May 27-29, 2025.
MICHAEL ADAMS is director of Corrosion Control Technical Support for NOV Tuboscope. He has more than 25 years of experience in technical sales and business development in diverse industries from electronics to coatings. His previous positions include sales management and business development with Valspar, Power Marketing Group, Commercial Resins Company, Cortest Laboratories, Johnson & Johnson and RCA Laboratories. Mr. Adams has served as chairman of the Task Group for Coated Reinforcement for ASTM International, chairman of the Epoxy Technical Committee for the Concrete Reinforcing Steel Institute (CRSI), chairman of the API Work Group for Mechanical Interference Connections and voting member of API 5L. He also serves as a member of American Water Works Association (AWWA) and AMPP. Mr. Adams earned a BS degree in chemistry from Trenton State College in Trenton, New Jersey.
REZA FARD is the Global Corrosion Control manager at NOV Tuboscope, where he supports the company’s high-performance internal plastic coatings product line. With more than eight years of experience in corrosion control, Mr. Fard has focused on both downhole and surface applications, helping operators understand and adopt coating technologies across the energy sector, including oil and gas, carbon capture and storage and geothermal. Before moving into the corrosion industry, he worked for five years as a Drilling Fluid specialist at SLB. He holds a BS degree in chemistry from the University of Texas at Austin.
MARK CANLAS is the Market Development director for Emerging Markets at NOV, where he focuses on geothermal and other non-traditional drilling opportunities. With over 20 years of experience in oil and gas, Canlas has built an extensive background in market development, commercial strategy and product launch execution. He has helped lead cross-functional teams in bringing new technologies from concept to market, ensuring they meet customer needs and deliver real-world impact.
LUTHER GRESSETT is a dedicated professional at NOV with expertise in driving operational excellence and supporting innovative solutions in the energy sector. With 17 years of experience and a strong background in collaboration and project execution, he plays a key role in advancing NOV’s mission of delivering cutting-edge technologies to its global customers. Mr. Gressett is passionate about problem-solving, teamwork and continuous improvement to create sustainable value.
JESSICA STUMP is a senior writer at NOV. She has written about the energy industry for more than 14 years. Ms. Stump has a bachelor’s degree in journalism from Texas Tech University.