Bridging the steam gap: A new playbook for geothermal integrity

TONEY DEER, Well Control School 

Fig. 1. As geothermal energy expands, industry experts are securing the future by standardizing the essential operational pivot from hydrostatic to thermodynamic control.

Geothermal energy has moved to center stage, as the world seeks reliable baseload power, and the industry is scaling up. However, this expansion has exposed a critical hurdle: a significant knowledge gap lies between the specific operational needs of geothermal wells and the established practices of the oil and gas (O&G) industry. While the surface equipment may look identical, assuming that conventional drilling methods transfer seamlessly to geothermal environments is a dangerous misconception. This gap represents a technical and systemic failure in training, material science, and well integrity that directly threatens the future growth, safety and economic viability of geothermal assets, Fig. 1. 

The fundamental disconnect lies in the objective. While geothermal operators rely on the O&G sector’s drilling equipment and basic operational concepts, their goal is fundamentally different: extracting heat from high-temperature, corrosive environments. This objective creates a unique risk profile that requires a distinct focus on well control and well integrity—one that standard O&G training and practices simply do not provide. To prevent the next major operational failure, the industry must move quickly to adopt specialized training and protocols that ensure safety and reliability. 

THE TECHNICAL CHASM: PRESSURE VS. TEMPERATURE 

The foundational difference between hydrocarbon extraction and geothermal energy production is the primary risk driver. In the O&G world, the primary focus is almost exclusively on managing formation pressure, to prevent an influx of fluids. In contrast, geothermal well management is dominated by the need to control the severe effects of temperature and complex fluid chemistry. This disparity creates a "technical chasm" that is most evident in three critical areas: well control, well integrity and material performance. 

The most immediate operational danger lies in the difference between a pressure kick and a steam flash. Conventional well control training focuses deeply on pressure management. When a driller encounters an influx in an oil well, the standard, ingrained response is to circulate and increase the mud weight, to regain control over the formation pressure. However, this approach fails in geothermal environments. In these operations, the primary danger is not a conventional kick but an aquathermal event, commonly known as a steam flash. 

Fig. 2. While an O&G kick is a pressure-volume issue solved by density, a steam flash is a temperature-phase issue solved by cooling. Treating a steam flash like a gas kick (by adding weight) can inadvertently accelerate condensation, triggering the vacuum collapse detailed in diagrams.

Geothermal wells contain superheated water or brine. If the hydrostatic pressure within the wellbore drops, this fluid can instantly vaporize into steam. The physics of this phase change demands an operational response that is fundamentally inverted from O&G standards. Where the O&G standard dictates increasing fluid density, the geothermal standard dictates cooling the well. Standard training, which emphasizes mud-weight methods, leaves personnel unprepared for this primary geothermal danger. To operate safely, personnel must be trained to rapidly recognize the precursors of a flash, react instinctively and execute cooling procedures to suppress the aquathermal event, Fig. 2. 

THE UNIQUE PHYSICS OF STEAM 

The introduction of a steam phase into the wellbore introduces severe hazards that are virtually unknown in conventional drilling. The first and perhaps most destructive is the risk of vacuum formation and implosion. If a steam-filled wellbore is suddenly cooled without proper pressure management, the steam rapidly condenses back into liquid water. Because steam occupies a significantly larger volume than water, this phase change results in an extreme volume reduction, creating a powerful vacuum inside the casing. This vacuum can be strong enough to cause the casing to collapse inward, resulting in catastrophic well failure, Fig. 3. 

Fig. 3. As shown in the transition from Step 1 to Step 2, the rapid condensation of steam results in a massive reduction in volume. This creates an instantaneous, severe pressure drop (vacuum) inside the wellbore. The resulting external pressure exceeds standard casing collapse ratings, leading to the structural failure seen in Step 3.

These risks require a delicate balance. If an operator applies too much pressure, they force the steam to condense. This eliminates the steam volume, but the sudden condensation triggers the very vacuum collapse they are trying to avoid. If an operator applies excessive hydrostatic or surface pressure, they can move the steam back below its saturation pressure, causing it to condense. While this eliminates the steam volume, the sudden condensation can rapidly create a vacuum risk, leading to the same collapse scenario. Consequently, the entire well control process is complicated by a constant, narrow balance between temperature, pressure and vacuum management. 

Compounding this complexity is the presence of Non-Condensable Gases (NCGs). When a well flashes, it often brings up NCGs mixed with the steam. Unlike steam, these gases do not condense when the well is cooled. Instead, they remain in the wellbore, forming toxic or explosive gas pockets that are difficult to remove and manage, posing an ongoing surface safety threat—even after the well appears stable. Furthermore, the cooling process itself presents the challenge of the "quenching front." If this front becomes unstable or retreats during a kill operation, the hot fluid can flash again, restarting the entire cycle of instability. 

INTEGRITY AND THE FATIGUE OF THERMAL CYCLING 

Beyond the immediate risks of well control, geothermal wells face long-term integrity challenges driven by thermal stresses—a problem far less pronounced in most O&G wells. Geothermal barriers are expected to function reliably through extreme and repeated thermal cycles for decades. The continuous expansion and contraction of the casing, the cement sheath and the surrounding rock are the primary drivers of long-term fatigue damage, Fig. 4.

Fig. 4. As the well cycles between the injection/kill phase (ambient/cold fluid) and the production phase, the well barriers are subjected to opposing physical forces. The transition creates a "tug-of-war" between high tensile stress caused by contraction and high compressive stress caused by expansion. Over time, this oscillation compromises the structural integrity of the well, leading to critical failures in the cement sheath.

Geothermal wells are frequently drilled into hard, fractured igneous and metamorphic rocks, which already create complex in-situ stress regimes. When the thermal stresses induced by production and injection cycles are added to this mix, the stress on the casing and cement becomes extreme. Standard O&G barrier philosophies—typically designed for relatively stable temperature environments—do not adequately address the durability needed to withstand this repeated thermal stress. 

This thermal environment also exposes the limitations of standard oilfield materials. Materials designed for O&G service can fail catastrophically in geothermal environments. For instance, ordinary Portland cement suffers from strength retrogression at temperatures above 110°C. To remain stable, geothermal cement must contain additives like silica flour and be designed to resist chemical attack from toxic or acidic fluids, including H₂S, CO₂ and brines. 

Similarly, metallurgy is tested to its limits. High temperatures reduce the tensile strength of steel casing. When combined with corrosive fluids, containing chlorides, CO₂ and H₂S, the result is often rapid metal loss or stress corrosion cracking. This environment often necessitates the use of expensive Corrosion Resistant Alloys (CRAs), to ensure longevity. Even the elastomers used in packers and seals are vulnerable; standard rubber compounds degrade quickly in high heat and frequently require advanced, non-elastomeric materials or metal-to-metal seals. A failure to understand these material limitations is a direct cause of well integrity failure and significant financial loss. 

THE WORKFORCE AND ACADEMIC DISCONNECT 

The technical gap is compounded by parallel deficiencies in the workforce and academic pipeline. The industry is currently struggling with a lack of specialized competency, among existing O&G transplants, the mass retirement of decades of geothermal experience and a lack of dedicated training pathways. 

Many engineers and field personnel entering the geothermal sector transfer directly from the oil patch. While they possess excellent drilling proficiency and foundational operational skills, their lack of specific geothermal experience requires a dedicated period of adaptation. The challenge is often "un-training" the conventional O&G mindset in areas where it conflicts with geothermal reality. For example, the instinctive reaction of an O&G driller to a well control event is to increase fluid density—the wrong response to a steam flash. Similarly, standard selections for casing, cement and packers often require significant temperature and chemical derating for geothermal service. 

Academically, the situation is equally fragmented. While the expansion of geothermal energy is critical for the energy future, academic institutions have lagged in establishing specific geothermal drilling and well integrity curriculums. Until recently, there was no standardized, internationally recognized training program dedicated to geothermal well integrity. The well control training industry has robust programs for O&G, but these programs fail to fully address unique geothermal failure mechanisms. This has left geothermal professionals unable to obtain training certificates verified against the necessary geothermal body of knowledge, which results in a fragmented industry where training is inconsistent or unavailable. 

THE COST OF THE GAP 

The consequences of this competency gap are severe, manifesting in higher rates of operational incidents—specifically geothermal well blowouts. Over the last 50 years, major geothermal blowouts have occurred globally, including in the United States, Philippines, Indonesia, New Zealand, Japan, Türkiye and Canada. 

Historical data reveals that geothermal well control incidents demonstrate distinct characteristics, compared to O&G. While O&G blowouts are often driven by unexpected high-pressure kicks, geothermal blowouts are overwhelmingly triggered by aquathermal events. Once a geothermal well is flashing and flowing steam, containment is vastly more complex than a conventional kick. The standard killing method involves pumping large volumes of water to cool the well, but this requires a sufficient and reliable water supply—a key risk factor that must be assessed before drilling begins. Furthermore, the risk of the quenching front retreating makes sustained well kill operations notoriously difficult. 

Long-term fatigue also takes a toll. Casing failures, often caused by thermal cycling, have been documented as a leading cause of long-term well failure in geothermal fields. While precise, publicly aggregated global statistics are difficult to obtain, compared to the highly regulated O&G industry, regulatory findings indicate that incidents are disproportionately high relative to the volume of wells drilled. This is largely due to the failure to adopt specific High-Pressure High-Temperature (HPHT) and thermal management protocols. The severity of these incidents underscores the urgent need for robust, specialized training. 

THE IADC SOLUTION: A NEW FRAMEWORK 

To address this critical knowledge gap, the International Association of Drilling Contractors (IADC), in collaboration with industry experts, is developing the Geothermal Drilling and Workover Well Integrity Supplemental Training Framework. This initiative represents a foundational shift, designed to address the sector's unique failure mechanisms. 

The framework focuses on establishing baseline competency for all personnel involved in critical geothermal operations. It ensures that engineers, supervisors and field personnel possess the specific knowledge base needed to manage unique geothermal risks safely and effectively. The technical content directly addresses the deficiencies of the past. Well control procedures emphasize cooling the well as the primary method for killing an aquathermal event. Well integrity modules cover the analysis of wellbore stresses caused by thermal cycling and adapt barrier philosophy for dynamic thermal conditions. Additionally, the framework provides specific training on material performance limitations regarding cements, metals and elastomers. 

A crucial component of this solution is the introduction of the IADC Geothermal Well Classification system. Tying the complexity of the well to mandatory safety equipment and procedures, this system functions similarly to API standards in the O&G industry. By defining a clear hierarchy of risk and required action, the classifications provide operators, engineers and regulators with standardized language to ensure the right equipment and training are applied to the right level of risk. 

CONCLUSION: SECURING THE FUTURE 

The expansion of geothermal energy is non-negotiable for a sustainable energy future. However, the operational demands driven by high heat, corrosion and severe thermal cycling create a unique and complex risk profile that the industry cannot ignore. The development of specialized frameworks—such as the IADC Geothermal Drilling and Workover Well Integrity supplemental training—is not merely a training exercise; it is an essential act of industry maturity. 

This standardization addresses the fundamental deficiencies in the workforce, ensuring that all personnel—from field hands to engineering supervisors—understand the unique physics of an aquathermal event and the material requirements for long-term well integrity. By defining clear expectations for equipment through well classification and mandating specialized knowledge through accredited training, the industry can secure a path forward. Adhering to these new standards is the only way to effectively manage geothermal-specific failure mechanisms, enhance safety and ensure the long-term technical and economic viability of these critical assets. Through these means, the steam gap can finally be bridged. 

TONEY DEER. With over 23 years in the industry, Toney Deer is currently Director of Training at Well Control School. He has extensive experience as an oilfield professional, specializing in operations management and complex drilling scenarios (HPHT, MPD, Geothermal, Horizontal) across the U.S., Iraq, and Yemen. In addition to his role as Director of Training, Toey is also a certified Senior Well Control instructor. He demonstrates industry leadership as the IWCF North American chapter secretary and a panel member for industry standard committees, including IADC, API and as Chair for the geothermal well control subcommittee.