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Non-productive time (NPT) in O&G can result in operators often losing from hundreds of thousands to millions of dollars. The need to maximize productivity—without sacrificing safety—drives the relentless pursuit to minimize the number of incidents that result in process downtime. Operators aim to reduce NPT by continuously seeking opportunities to improve efficiency, which fuels the demand for new advancements in technology. This increases the complexity of the equipment used in hydrocarbon field development, and creates an even greater need for state-of-the-art technologies. But with each more complex system comes new failure modes that maintenance engineers have never seen before. Optimizing equipment potential requires that maintenance upgrades and processes are continuously keeping pace with equipment advances.

The downhole environment has always been hostile for drilling, logging, and production equipment, yet operators continue to push the boundaries, trying to drill deeper, longer wells with complex profiles and higher pressures and temperatures. At the same time, profitability requires diligence in controlling overall project costs. These conflicting demands are complicated by the extreme variability in downhole conditions between basins.

For example, when I was developing maintenance programs for equipment in the Gulf of Mexico, where some oilfields have downhole pressures exceeding 25,000 psi and downhole temperatures close to or above 150 degrees Celsius (150 C), I had to tailor our maintenance tactics to meet the demands of the anticipated conditions. Electronic components had to pass rigorous examination and testing at temperatures close to the expected operating environment. Mechanical components underwent pressure testing at the expected pressure plus a safety factor, followed by dimensional and dye penetrant inspections to identify any plastic deformations or cracks.

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Figure 1: Hot spot on an electric circuit identified by infrared camera indicates a failure of one of the components. Source: Denis Eremenko

Conversely, wells drilled in Sakhalin Island (Russia) presented different challenges. Several oil fields are located under the sea bed, close to the shore, so that the operators chose to develop them from on-shore drilling rigs. To reach the reservoir, well profiles had to include long horizontal sections, up to several thousand meters, however, the vertical depth of such wells remained relatively low, so that pressure and temperature were no longer a concern. Because equipment longevity became a higher priority, I adapted the maintenance program for these conditions with customizations including tighter dimensional tolerances for the mechanical parts, implementing local design upgrades so that the parts could withstand longer operating intervals, protecting components exposed to drilling fluid flow from erosion by applying erosion-resistive coatings, and/or changing the parts that were in contact with the borehole to incorporate more abrasion-resistant components.

Operating oil and gas equipment at the highest level of reliability in a hostile environment requires development, implementation, and continuous improvement of a maintenance program adequate to the challenge, so that complex systems remain operational over extended periods of time. The following key components of a successful maintenance program will help engineers and operators unlock equipment potential and minimize failure rates.

1. Configure the equipment to the project’s environmental requirements

It is important to learn about operating conditions, especially when preparing equipment for a job in an unknown field, with little to no past experience. While it is impossible to exactly predict all operating parameters, the best estimate of key factors such as temperature, pressure, formation type, and planned mud type and chemistry plays a crucial role in the planning phase.
Operations in remote regions with rough road surfaces, such as those that I encountered in Sakhalin, require rugged packaging/crating when equipment leaves the maintenance facility, to protect it during transit. When exposed to extremely low temperatures, elastomers may become brittle, fluids used in the equipment’s hydraulic systems may freeze, and grease may harden—making it difficult to unscrew threads. While drilling equipment is designed for operations above 0 C, it can be subjected to lower temperatures in transit or during storage, however, freezing conditions may be detrimental if the risks are not evaluated thoroughly.

Ambient humidity is another factor that could affect the performance of electronic components if the maintenance facility is not climate-controlled in hot and humid environments. For some locations like the North Sea or Sakhalin, the summer period is very short and the overall exposure to humidity is low, while in others, like Southeast Asia or the Gulf of Mexico, electronics may start to deteriorate when stored in facilities with humidity exceeding 60%. Assessing the environment in the workshop and implementing adequate controls (installing humidity monitoring devices and dehumidifiers) should be viewed as a required investment into equipment reliability. Maintaining state-of-the-art equipment that is expected to perform at the highest levels raises the bar for the maintenance facility standards.

2. Monitor equipment performance on the job in real-time

Self-diagnostic data or external sensors mounted on the equipment allow operators to monitor the health of the ongoing activity, and detect early signs of equipment malfunction. For example, if thermography identifies an unusually hot component on an electronic board during electronic cartridge maintenance (Figure 1), the board could be preemptively replaced before it fails on a drilling run and causes significant downtime and losses.

For electronic components, parameters such as total current consumption and dissipated heat serve as good indicators of circuitry health. Mechanical components that are in motion can be evaluated by the noise or vibrations at the system level, or by the power demand required to set the system in motion.

The downhole environment has always been hostile for drilling, logging, and production equipment, yet operators continue to push the boundaries, trying to drill deeper, longer wells with complex profiles and higher pressures and temperatures. At the same time, profitability requires diligence in controlling overall project costs. These conflicting demands are complicated by the extreme variability in downhole conditions between basins.

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Figure 2: Stabilizer blade with conventional tungsten carbide tiles (left), and abrasion resistant TSP (thermally stable polycrystalline) tiles (right). Source: Denis Eremenko

For example, when I was developing maintenance programs for equipment in the Gulf of Mexico, where some oilfields have downhole pressures exceeding 25,000 psi and downhole temperatures close to or above 150 degrees Celsius (150 C), I had to tailor our maintenance tactics to meet the demands of the anticipated conditions. Electronic components had to pass rigorous examination and testing at temperatures close to the expected operating environment. Mechanical components underwent pressure testing at the expected pressure plus a safety factor, followed by dimensional and dye penetrant inspections to identify any plastic deformations or cracks.

Conversely, wells drilled in Sakhalin Island (Russia) presented different challenges. Several oil fields are located under the sea bed, close to the shore, so that the operators chose to develop them from on-shore drilling rigs. To reach the reservoir, well profiles had to include long horizontal sections, up to several thousand meters, however, the vertical depth of such wells remained relatively low, so that pressure and temperature were no longer a concern. Because equipment longevity became a higher priority, I adapted the maintenance program for these conditions with customizations including tighter dimensional tolerances for the mechanical parts, implementing local design upgrades so that the parts could withstand longer operating intervals, protecting components exposed to drilling fluid flow from erosion by applying erosion-resistive coatings, and/or changing the parts that were in contact with the borehole to incorporate more abrasion-resistant components.
Operating oil and gas equipment at the highest level of reliability in a hostile environment requires development, implementation, and continuous improvement of a maintenance program adequate to the challenge, so that complex systems remain operational over extended periods of time. The following key components of a successful maintenance program will help engineers and operators unlock equipment potential and minimize failure rates.

Because the importance of health monitoring requirements increases with the complexity of the hardware and software, state-of-the art equipment often has self-diagnostic functions implemented at the design phase.

3. Assess equipment condition after a job

Even a failure-free operation of complex equipment provides ample opportunities to ensure flawless execution in the future.

• Analyze recorded information: recorded sensor data may provide better resolution compared to real-time monitoring, due to higher data recording frequency, or a larger spectrum of recorded parameters. When analyzing bearing performance, I noticed that a failing bearing may induce additional vibrations that increase with time. It might be difficult to recognize when monitoring over a short interval, however, this indicator becomes more obvious when analyzing the trend over a longer period of time.

• Check for out-of-spec environment, adjust maintenance based on exposure: at times, equipment operating environments can be extreme and change so drastically that assets are working in conditions beyond what they were designed for, yet this may not result in a hardware failure. Assets exposed to out-of-specification conditions during a job may sustain unusual wear, which can reveal weak points in the design. On one of the wells drilled in Sakhalin, drilling tools passed through a layer of extremely abrasive formation that accelerated wear on the equipment components in contact with the wellbore. Analyzing wear patterns from that interval provided valuable information on how to improve the design and extend the life of the parts even for regular application, allowing drilling for longer sections in less abrasive formations. One of the solutions that came out of this analysis was the application of improved wear-protective tiles on stabilizer blades, that stabilize the downhole tool assembly in the wellbore and are in contact with the formation (Figure 2).

• Evaluate mechanical components during disassembly or testing: benchmarking components’ wear against typical wear seen on similar modules after an average job facilitates identifying parts that are exhibiting unusual and/or previously unseen wear patterns. As depicted in Figure 3, bolts that secure parts and modules together typically show little wear, but exposing equipment to high shocks and vibrations during downhole runs may result in bolts deformation and/or thread elongation. This serves as a first indicator of exposure to harsh environments, and is a trigger to replace all bolts before they fracture and fail—even those that are not yet showing any signs of deformation, but have accumulated some fatigue. Such vigilance allows maintenance technicians to recognize new failure modes before they result in an actual loss to operations, as equipment ages through its lifecycle. 

4. Adapt the maintenance program for early detection of potential failure onset

Defining maintenance tasks, and time (or event) triggers for these tasks, is the foundation of any successful maintenance program. System function tests, equipment disassembly requirements, and oil replacement intervals should all have the underlying goal to identify and prevent a potential failure at its infancy. The detection techniques range from visual inspections and non-destructive testing, to condition-based monitoring – such as bearing vibration measurements or oil contamination analysis. The key is to establish a baseline for the monitored parameter during regular performance (for instance, certain vibration levels of an electrical motor, or the allowable amount of oil contamination in the lubricating system of the module), and a threshold, which - when surpassed - will trigger part replacement or an advanced level of disassembly and increased maintenance, to bring the system back to a “safe zone.”

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Figure 3: Attention to small details such as unusual bolt wear may yield great benefits by preventing costly equipment failures.

5. Develop and implement design improvements to extend operations in the “safe zone”

Once the wear of the components or parts failure is identified and evidence is captured, the engineering team should explore the opportunities for design improvement. Limited resources allocated to equipment maintenance and reliability upgrades demand a well-considered implementation. The key is to define the initial plan, take into account the procurement process, parts lead time, and time required to implement the upgrade, and to perform periodic reviews to stay focused on the progress, re-adjusting the plan as needed. A simple spreadsheet can be sufficient to lay-out the plan and track the progress.

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Figure 4: The maintenance trigger must be set so that it would bring the system back to the safe zone, while not happening prematurely, which in turn may lead to maintenance-induced errors and increased spend on consumables.

6. Successful maintenance program execution depends on people

The most critical element of a successful maintenance organization is the team of people responsible for executing maintenance processes.

• Develop, coach, and mentor maintenance technicians: sophisticated technology is unique and complex by design, requiring specialized knowledge and skill-sets that can only be gained through theoretical training and exposure. Mastering technical and workmanship skills may take years. A comprehensive training program will allow for new hires to absorb the required knowledge, and embrace the philosophy of adhering to established maintenance processes.
To foster a culture of knowledge sharing, I implemented a system of knowledge champions within the maintenance department. Technicians with many years of experience in the specific technology were selected for these roles, with a set of objectives to drive the culture of excellence and act as the main point of contact for knowledge sharing for the respective technology, both within the local maintenance team and externally with the engineering center.

• Promote knowledge sharing with engineering: two-way communication is crucial between technicians and the engineering team, which relies on the feedback from the shop floor to understand common wear patterns. Implementing reliability improvements designed by the engineering department requires a knowledge sharing workflow that enables the timely review of updated documentation, communication to all members of the maintenance team, and adoption in the routine maintenance processes - like the one shown on Figure 5. Sign-off sheets help to ensure that no one is overlooked due to vacation or sick time.

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Figure 5: Communications workflow to review engineering releases with all maintenance technicians. Source: Denis Eremenko, icons by Freepik (flaticon.com).

Conclusion

Developing a mature maintenance program with a focus on equipment reliability is a multi-year journey. Any organization committed to this journey must be willing to learn from the experience and continuously adjust, weaving the ongoing improvements into the maintenance processes. Multiple, intertwined building blocks are necessary for success, and when properly implemented the process will drive outstanding levels of asset reliability.

These recommendations were developed from years of experience maintaining state-of-the-art equipment operated in hostile environments in oil and gas, however, these steps can provide the foundation for a maintenance organization in other industries in which the relentless pursuit of high equipment reliability will have a positive impact on the bottom line.

  Text and images: Denis Eremenko