Engineered components are the difference between survival and failure in HPHT subsea systems

GARRY MACDONALD, Greene Tweed 

Fig. 1. Sitting more than 10,000 ft below surface level, extraction equipment can be subject to extreme pressures.

The search for oil and gas beneath the seabed has never been gentle. Offshore drilling has always carried risks, but as exploration ventures into deeper waters and hotter reservoirs, the challenge becomes almost brutal. High-pressure, high-temperature (HPHT) wells are becoming the norm. Every piece of equipment, no matter how small, is expected to withstand conditions that punish weakness and expose flaws, Fig. 1. 

At depths of several thousand meters, the environment is shaped by extremes. Pressures build to crushing levels, capable of distorting metal housings or forcing fluids through the slightest imperfection in a seal. Below the seabed floor, temperatures can climb beyond 250°C, sometimes nudging closer to 300°C—enough to exhaust the strength of conventional polymers and accelerate the corrosion of metals. Add to this a soup of water, gas and corrosive chemicals, and the result is an operating environment that leaves no room for error, Fig. 2. 

Offshore, failure is not an option. On land, repairs might be inconvenient; at sea, they demand heavy-lift vessels, remotely operated vehicles or specialist diving crews. Costs can spiral by the day, often by the hour, while lost production adds another layer. A stalled electrical submersible pump (ESP), caused by a failed connector or a compromised insulator, does not just stop working; it halts the well itself. In a high-producing field, the revenue lost in a week can exceed the annual budgets of smaller projects. 

Reliability offshore is inseparable from safety. Blowout preventers, control pods and subsea valves all form barriers that no operator can afford to see breached. If a seal loses its integrity or an electrical termination is weakened by moisture ingress, the system’s ability to respond to a crisis is undermined. The implications stretch far beyond one well or one operator: reputations, regulatory standing and public trust are all at risk. In a recent collaboration on Baker Hughes’ SeaPrime MUX blowout preventer control system, Greene Tweed worked side by side with the OEM to deliver pressure-ready electrical harness assemblies that combined Seal-Connect^® connectors with sealed, booted splices to protect terminations from contamination and signal loss—a design later validated through both signal and pressure testing.

Fig. 2. Greene Tweed's sealing solutions can effectively counteract challenges commonly faced in the subsea production system.

The program moved beyond components to a turnkey harness. Greene Tweed’s applications, process and assembly teams co-developed an instrument loom for 1 atm pressurized housings, routing more than 80 individually labeled conductors and replacing epoxy-potted interfaces with elastomeric-booted splices, to mitigate moisture ingress and extend splice life. The assembly paired a Seal-Connect^® multi-pin connector in Arlon^® 2000 (PEK) with contact blocks in Arlon^® 1000 (PEEK) and Fusion™ 755 (FKM) boots, simplifying the electrical architecture, reducing conductor count to the instruments and making field service faster and cleaner. Two complete assemblies were delivered on schedule and then taken through layered validation, including signal continuity and pressure tests. The instruments delivered their data streams to the control system under the harshest conditions. 

As control systems push farther from topside and demand faster telemetry for diagnostics, imaging and closed-loop actuation, operators are shifting from copper to fiber-optic links to gain bandwidth, lower latency and immunity to electrical noise at depth. That move only works, if the optics stay dry and precisely aligned. Seal-Connect^® single-fiber interconnection addresses the wet, high-pressure environment, with FC and ST terminations that use precision-machined zirconia ferrules and alignment sleeves for repeatable core-to-core mating, with typical insertion loss ≤0.5 dB per connection. FC and ST are standard single-fiber formats: FC uses a threaded, position-keyed screw coupling for a secure mate, while ST uses a bayonet twist-lock “j-slot” for a quick engage and disengage. 

Greene Tweed’s DRY/DRY HP designs seal fiber connections against pressure and temperature extremes, while bulkhead feedthroughs maintain signal integrity across subsea barriers. For higher channel counts or harsher duty, the Fiber Optic Extreme^® line offers rugged, low-loss options for reliable data transfer in confined subsea spaces. 

Vast structures, such as risers and wellheads, are built with redundancy and strength in mind, yet small components can impact operational success. For instance, an O-ring that loses elasticity after repeated heating and cooling, or an insulator that cracks under pressure, can start a chain reaction that ends with system failure. A component worth a fraction of a percent of total project costs can jeopardize billions of dollars of investment. 

As drilling moves farther offshore and into harsher reservoirs, the importance of these small parts becomes clearer. The economics of subsea projects are already under strain from fluctuating prices and growing scrutiny of carbon intensity. Downtime damages profitability and adds to emissions, as vessels and rigs burn fuel to stand idle. Longevity of equipment is, therefore, both an environmental and operational question. The longer that critical assets run without intervention, the stronger the case for their continued role in the global energy mix. 

In a challenging environment, success does not depend on how large or complex a system appears on the surface but on the reliability of its smallest components. Seals, insulators and connectors, hidden out of sight, determine whether subsea production remains steady, safe and sustainable, or whether it falters under the pressure of the world’s harshest operating conditions. 

WHERE TRADITIONAL MATERIALS FALL SHORT 

For years, the offshore sector relied on the same selection of metals, rubbers and polymers. These materials did the job well enough in shallower, less hostile wells, but in the harsher environments operators face today, those materials are running out of headroom. As a result, those materials that were once dependable now come into question. 

Metallic components corrode when exposed to sour gas or aggressive brines. Elastomers lose their resilience when stretched and squeezed at an extreme temperature for months on end. Polymers soften, creep or fracture, as heat and pressure mount. The changes can be almost invisible at first: a tiny crack, a slow loss of elasticity or a dip in electrical resistance. In an offshore well, these subtle weaknesses never remain isolated. A crack opens the door for fluids, and a shortfall in insulation turns into failure. 

ESPs, in particular, highlight this fragility. Sitting thousands of feet down, they are often the only way to lift hydrocarbons from the reservoir. Their motors, stators and connectors face relentless heat, pressure and fluid exposure. In their case, traditional polyimide insulators proved inadequate. Machined from rod stock, they imposed long lead times and design limitations, and worse still, they allowed water to creep in. Even a trace of moisture was enough to break down the insulation and bring the pump down, cutting production and sending costs skyward. 

Subsea control systems showed a similar pattern. Blowout preventer pods and valve assemblies cannot afford even momentary lapses, yet their electrical terminations were often left exposed. Further, disorganized wiring left room for contamination. The result was signal loss and, eventually, system failure. In safety-critical equipment, that risk is intolerable. The imbalance is stark; a low-cost connector can bring down equipment worth tens of millions, with pumps designed to run for years failing in months. 

The conclusion is unavoidable: the old set of materials has reached its limits. Components that worked in conventional wells no longer survive in HPHT conditions. They have to be re-engineered if subsea production is to continue. 

REDEFINING MATERIAL PERFORMANCE THROUGH ENGINEERING INNOVATION 

When older materials reached their limits, the industry faced a challenge. Pushing equipment deeper and hotter would not work, if the smallest parts could not keep up. A leaking seal or cracked insulator could bring down an entire system, and incremental fixes were no longer enough. 

Redefining performance started with materials. Traditional polymers had done well in milder conditions, but the new generation of HPHT wells demanded something tougher. Crosslinked thermoplastics and advanced elastomers were built from the outset to endure extremes that destroyed earlier options. These marginal upgrades were engineered with heat and pressure in mind from the beginning. 

The transformation that ensued was clear in the case of ESPs. For years, ESPs relied on polyimide insulators. This material had several limitations: machining was slow, geometry was constrained, and water ingress was inevitable. A single trace of moisture could destroy insulation and trigger failure, forcing operators into downtime and costly replacements. 

Cross-linked PEEK changed that landscape. It maintains insulation at 260–300 °C and can be molded into complex geometries, rather than machined from stock, giving designers the freedom to create water-tight insulators from the outset. A series of coupon tests, prototypes and, finally, injection-molded parts, confirmed the improvement. In parallel, connectors and feedthroughs followed the same materials path: Greene Tweed’s Seal-Connect® line combines engineered sealing with high-performance thermoplastics, such as Arlon® 3000XT, providing durable internal seals, stable electrical properties and lower weight for demanding HPHT service, in addition to single- and multi-pin, coax and wet-stab options for subsea and energy use. The pump was never the issue; the material and interface were. 

Fig. 3. Subsea equipment on the ocean floor.

Once installed, the difference was clear. Pumps ran longer, resisted moisture ingress and delivered consistent performance. Economics shifted alongside engineering, with ESPs treated as reliable assets rather than consumables, and costs dropped, because equipment lived up to its intended design life. 

While it is easy to overlook the role of materials in subsea engineering, in this case they defined the outcome. Rethinking polymers gave engineers the freedom to build components that could survive intense HPHT stress. In a sector where billion-dollar projects can hinge on millimeters of insulation, that freedom is survival, Fig. 3. 

SYSTEMS THINKING FOR SUBSEA RELIABILITY 

Even the strongest material can only go so far, if the system around it is flawed. Reliability offshore is never the product of a single part in isolation. Rather, it depends on how components are integrated and protected in assemblies designed to endure. Subsea control systems underline this point. 

Blowout preventer pods form the ultimate safety net in drilling operations. However, early designs often left electrical terminations exposed. Each wire ran its own course and was unprotected and challenging to manage. As a result, servicing was messy, contamination was inevitable and as soon as fluids found a path inside, signal integrity faded. Reliability—and safety—was compromised by something as basic as wiring management, Fig. 4. 

Fig. 4. Connectors transfer electrical signals in harsh, downhole environment conditions through a pressure barrier in the subsea electronics module within various pieces of equipment.

The solution was to deliver complete harness assemblies, not loose wires. Instead of asking operators to manage dozens of terminations offshore, the assembly was sealed, labeled and tested in advance. Booted splices, epoxy potting and engineered seals created interfaces resistant to moisture ingress, far beyond traditional options. 

Collaboration with equipment manufacturers showed just how effective this solution could be. More than 80 wires had to be routed and protected, each carrying critical signals, but with a turnkey assembly, installation was faster, servicing easier and reliability proven through pressure testing. For the operator, the payoff was confidence that safety-critical systems would deliver when needed. 

Systems thinking removed opportunities for contamination, simplified maintenance and extended service life. Harnesses tidied wiring and changed the reliability profile of the entire control system. Resilience came from treating the system as a coherent whole instead of depending on one clever component. 

EXTENDING EQUIPMENT LONGEVITY AS AN ECONOMIC AND SUSTAINABILITY IMPERATIVE 

For operators, longevity is measured in projects and production. When Baker Hughes developed its SeaPrime MUX blowout preventer control system, the company knew electrical integrity could not be compromised. Loose wiring and unprotected terminations were a threat to both uptime and safety. By introducing sealed harness assemblies, the system maintained signal integrity under repeated pressure cycles and resisted the contamination that had undermined earlier designs. The result was a pod that operators could trust. 

In the downhole environment, a global oilfield services company experienced constant ESP failures, due to polyimide insulators. Switching to molded crosslinked thermoplastic gave the pumps a second life. They lasted longer, ran consistently and avoided the moisture ingress that had crippled earlier designs. Costs fell as unplanned interventions declined, and production stabilized. 

Sustainability adds weight to the argument for the switch. Every intervention offshore demands vessels, fuel and manpower, with each unplanned trip carrying a carbon footprint. A connector that lasts five years instead of two avoids multiple callouts, saves emissions and reduces waste from discarded parts. That longevity now influences both economic and environmental performance. 

Regulators and investors are also demanding proof that assets can endure. Reliability is becoming a measure of responsibility, as much as engineering capability. Baker Hughes and others illustrate that point. Better components extend service life and reduce risk, and they strengthen the case for subsea production in a world that demands ever greater efficiency with lower environmental impact. 

LOOKING AHEAD: THE FUTURE OF SUBSEA COMPONENT DESIGN 

As of this writing, the industry’s trajectory points towards deeper waters, higher pressures and hotter wells. The reality of resource development is that conventional reservoirs are maturing, leaving operators to target reservoirs that demand more from their equipment than ever before. The margin for error continues to shrink, and with it grows the importance of engineering at the smallest scale. 

Future subsea systems will need to withstand harsher environments and integrate with digital tools already spreading across offshore operations. Sensors, data streams and predictive maintenance depend on connectors and insulators that do not falter. A faulty termination can compromise an entire monitoring chain. The physical integrity of materials underpins the effectiveness of the digital twin. Without reliable inputs, models are meaningless. 

Material science will continue to evolve. The experience gained with crosslinked thermoplastics and chemically resistant elastomers is being extended into new polymers that resist both heat and chemical exposure. Meanwhile, composites are advancing, offering strength without the weight or corrosion of metals. These are steady gains that make subsea systems less fragile and more predictable. 

The industry’s culture is shifting as well. Components can no longer be treated as consumable; they are strategic assets shaping the economics and sustainability of entire fields. Designing them to last is a commercial necessity and a regulatory expectation. 

The future of subsea production will not be decided by the scale of platforms or the power of pumps. It will depend on how well the smallest parts endure. Those decisions, set at the design table and measured in millimeters, will define whether or not projects remain viable, sustainable and safe. 

SMALL PARTS, SIGNIFICANT CONSEQUENCES 

Subsea engineering is judged by the scale of visible equipment and by the survival of seals, insulators and harnesses hidden from view. High-pressure and high-temperature environments punish weakness quickly, and small details can decide whether systems continue or collapse. 

In Baker Hughes’ SeaPrime MUX blowout preventer control system, sealed harness assemblies with booted splices and carefully routed conductors held their signals through pressure cycles and contamination risk. The same discipline of hardening the weak links in hostile environments carries downhole. In artificial lift, a global oilfield services company moved from rod-stock polyimide to injection-molded insulators made from Arlon 3000XT—a cross-linked PEEK formulated for extreme temperatures. The material maintained electrical resistance and dimensional stability at 260–300 °C, resisted fluid aging and, crucially, could be molded into watertight geometries that cut moisture ingress, while reducing lead time and total cost of ownership after a staged program of coupon tests, machined prototypes and production validation. 

As projects move into deeper and hotter environments, components cannot be dismissed as mere consumables. They are, instead, levers for improving uptime and safety and reducing emissions. Every avoided callout saves fuel, reduces waste and strengthens the economics of offshore production. The big structures will always draw attention, but resilience is earned at the millimeter scale, in the drawings where connector profiles and material grades are set. That is where longevity is secured. 

GARRY MACDONALD is a Global Product manager at Greene Tweed, responsible for Seal-Connect^® electrical and optical sealed interconnect solutions, designed to withstand the harshest environments. He has over 20 years of experience in the global connector industry, with a focus on harsh environment applications in the energy, defense and subsea industries.