Innovative chemistry and customized approaches can overcome critical challenges, from severe corrosion in high-stress environments to sudden and unexpected scale formation in high-temperature “dry” production wells, extending equipment life and ensuring production reliability, even in the most demanding environments.
DR. ALEX THORNTON and DR. NIHAL OBEYESEKERE, Clariant Oil Services
As offshore oil production ventures into increasingly demanding environments, operators face unprecedented challenges in maintaining asset integrity. High temperatures, extreme pressures, and complex fluid chemistries create adverse conditions that can accelerate corrosion and scale formation, threatening production reliability and safety.
These challenges require innovative chemical solutions that perform under conditions where conventional treatments fail. This article examines how specialized chemical treatments are evolving to address the most severe corrosion and scale challenges in offshore operations.
GROWING COMPLEXITY OF OFFSHORE PRODUCTION ENVIRONMENTS
Today's offshore operations frequently encounter conditions that push the boundaries of traditional chemical treatment approaches. Deepwater assets, high-temperature reservoirs, and complex production chemistries create scenarios where more is being asked from standard inhibitors. When these challenges emerge in remote offshore locations with limited intervention options, the consequences of treatment failure can be severe—from production losses to devasting equipment failures.
Addressing these extreme scenarios requires a fundamental shift in chemical treatment philosophy. Rather than applying generic solutions at higher concentrations, success depends on developing specialized chemicals designed specifically for these challenging environments, coupled with application expertise that ensures optimal deployment.
CASE STUDY: COMBATING HIGH-SHEAR CORROSION IN SUBSEA WATER INJECTION SYSTEMS
A major operator in the Asia-Pacific region faced a critical integrity threat, when alarming corrosion rates were discovered in a subsea water injection system. Uninhibited corrosion rates exceeded 5 mm/year, with significant wall loss at high-shear locations like the "goose neck" identified during ultrasonic testing inspection. Without effective mitigation, engineers projected a through-wall failure within just 12 months.
The situation presented multiple challenges that conventional treatments could not address:
Extreme shear stress conditions (100-130 Pa) that would strip away traditional corrosion inhibitor films.
Limited deck space and bulk storage capacity at the remote offshore location.
A critical 9-12-month treatment window while awaiting corrosion-resistant alloy (CRA) spool replacements.
Strict performance requirements, including an inhibited corrosion rate below 0.5 mm/year under high shear conditions
Following a comprehensive Best in Class evaluation process (Table 1), CORRTREAT 17557 emerged as the only solution capable of meeting all key performance indicators. Laboratory testing employed multiple methods to validate performance, including Rotating Cylinder Electrode for low-shear screening, Jet Impingement to assess product persistence under variable high-shear conditions, and High-Pressure Rotating Cage Autoclave (Fig. 1) to evaluate performance under field temperature and pressure conditions.
This solution was distinguished by its ability to maintain protective film integrity under very high shear stress conditions, where conventional inhibitors would be stripped away. Under high shear stress (130 Pa) in jet impingement testing (Table 2), the product achieved 96% protection efficiency at just 75 ppm, with a corrosion rate of only 0.15 mm/year—significantly below the 0.5 mm/year acceptance criterion.
The specialized formulation also addressed the logistical constraints of the offshore platform. As a highly active product with high flashpoint, excellent material compatibility, and low viscosity, it minimized the volume of corrosion inhibitor required for transport and storage offshore, reducing expenditure on tank rental and minimizing crane lifts.
CASE STUDY: SCALE MANAGEMENT IN HIGH-TEMPERATURE CHALK FIELDS
Scale formation presents a different but equally challenging threat to production integrity. In a high-temperature chalk field, operators encountered unexpected calcium carbonate scale formation at wellhead choke valves, despite operating in what should have been an acidic pH environment. The situation was particularly puzzling, as production had continued for a decade without scaling issues.
Investigation revealed a complex scenario:
Very high CO2 content (>45 mol%) and significant H2S in the gas
Very low water cut (<1%) for the first 10 years, followed by rapid increases
Low salinity well water with sparse, poor quality analysis data
Ongoing produced water reinjection (PWRI) and produced gas reinjection (PGRI) operations with blended water sources.
The sudden appearance of scale coincided with increasing water production, but the absence of free water in test samples complicated diagnosis and treatment. When scale formation progressed from surface equipment to downhole environments, the operator required a rapid solution to prevent production losses.
Traditional approaches to scale treatment design were ruled out, due to urgency:
Lengthy formation damage coreflood experimentation
Squeeze treatment modeling using historical field data
Extensive reservoir characterization studies.
Instead, Clariant and the operator developed a collaborative approach to squeeze design, with each parameter carefully optimized through rigorous question-and-answer sessions over several months. This process allowed for the development of a concept design addressing the field's unique challenges without conventional testing methods.
The solution centered on SCALETREAT 19071, a specialty squeeze scale inhibitor formulated specifically for high-temperature applications, Fig. 2. This innovative chemistry was designed to achieve significant squeeze lifetime while minimizing impact on the sensitive chalk matrix. The treatment approach balanced effective scale inhibition with minimal formation damage risk, a critical consideration in virgin wells with no previous chemical exposure.
Results validated the innovative approach:
Successful prevention of calcium carbonate scale formation downhole
Achievement of squeeze treatment lifetime design targets
Safe treatment application and well recovery in a virgin well environment
No formation damage, based on post-squeeze water surveillance and system parameter analysis
Positive secondary impact on existing topsides wellhead choke scaling.
THE EVOLUTION OF CHEMICAL TREATMENT PHILOSOPHY
These case studies illustrate a fundamental shift in the approach to chemical treatment for extreme environments, moving away from dosage increases of existing chemicals towards a holistic assessment coupled with tailored product design. This evolution in treatment philosophy encompasses several key principles.
1. Comprehensive problem analysis. Effective treatment begins with thorough characterization of the operating environment and failure mechanisms. This includes understanding not just the immediate symptoms but the underlying physical and chemical processes driving corrosion or scale formation. In the corrosion case study, this meant quantifying shear stress conditions and identifying critical failure points in the subsea system. For the scale treatment, it required determining the precise conditions triggering calcium carbonate precipitation despite seemingly unfavorable pH conditions.
2. Laboratory validation under field-representative conditions. Traditional laboratory testing often fails to replicate the extreme conditions encountered in modern offshore operations. Effective solutions require testing protocols that accurately simulate field conditions, including temperature, pressure, and fluid composition, and mechanical factors like shear stress. The corrosion inhibitor evaluation employed specialized high-shear testing methods like Jet Impingement to ensure performance under the extreme conditions present in the subsea injection system.
3. Customized application strategies. Even the most effective chemistry may fail to achieve the required KPIs if not applied properly. Successful treatments require deployment strategies tailored to the specific asset configuration, operational constraints, and treatment objectives. In the scale squeeze case, this meant developing an innovative approach that balanced effective inhibitor placement with minimal formation damage risk, despite limited reservoir characterization data.
4. Balancing performance with operational constraints. Offshore operations face unique logistical challenges that impact chemical treatment options. Limited storage capacity, restricted transportation options, and minimal intervention opportunities create constraints that must be considered in treatment design. The corrosion inhibitor case demonstrated how a highly active formulation could deliver effective protection at lower dosage rates, addressing the platform's storage limitations while maintaining performance.
FUTURE DIRECTIONS IN CHEMICAL TREATMENT TECHNOLOGY
As offshore operations continue to push into more extreme environments, chemical treatment technologies must evolve to meet these challenges. Several promising directions are emerging, as follows.
Multifunctional formulations. The next generation of treatment chemicals will increasingly combine multiple functionalities in single products, reducing the total chemical inventory required offshore while addressing complex production challenges. These formulations will go beyond the traditional combined corrosion and scale inhibitors and may include additional third components such as scale dissolvers, scavengers and emulsion breakers.
Environmentally enhanced solutions. Environmental regulations continue to tighten globally, driving development of more biodegradable, less bioaccumulative, and lower toxicity treatment options. Future formulations will need to balance performance in extreme conditions with improved environmental profiles, particularly for operations in sensitive marine environments.
Digital integration and predictive treatment. Advanced monitoring technologies and digital twins are enabling more precise application of chemical treatments. Real-time corrosion and scale monitoring, coupled with predictive analytics, allows operators to optimize treatment timing and dosage rates, maximizing effectiveness while minimizing chemical consumption. An example of such a holistic platform to monitor chemical performance is Clariant’s ChemVision.
Extended-release technologies. For remote and subsea applications, where intervention opportunities are limited, extended-release technologies offer promising solutions. These approaches provide sustained protection over longer periods, reducing the frequency of treatment operations and extending asset protection between maintenance windows.
CONCLUSION
The challenges of corrosion and scale management in offshore operations continue to intensify, as production moves into more extreme environments. Conventional treatment approaches are increasingly inadequate for these conditions, necessitating specialized solutions designed specifically for high-temperature, high-pressure, and high-shear applications.
Success in these environments requires more than innovative chemistry—it demands a comprehensive approach that combines specialized formulations with application expertise and thorough understanding of the operating environment. The case studies presented demonstrate how this integrated approach can deliver effective protection, even under the most challenging conditions.
As the industry continues to push boundaries in offshore production, chemical treatment technologies remain a critical enabler, allowing operators to maintain asset integrity and production reliability in environments once considered beyond the reach of conventional solutions. By embracing innovation in both chemistry and application methodology, operators can overcome even the most extreme corrosion and scale challenges in offshore operations. WO
DR. ALEX THORNTON is Global Innovation manager, Scale Technology, at Clariant Oil Services. In 35 years, he has advanced scale technology application and molecular development and has also played a prominent role in authoring and presenting a variety of innovative scale-related technical papers at oilfield conferences across the world. Dr. Thornton’s current role still involves travelling to support business units on-site and in-field, where he has developed a significant reputation for scale-related forensic analysis. This work focuses on resolving challenging downhole and topsides processing issues in the UK and Scandinavian sectors of the North Sea, along with the Middle East, South America, Africa, Asia and Eastern Europe.
DR. NIHAL OBEYESEKERE is Global Innovation manager, Integrity, at Clariant Oil Services. With a Ph.D. in Organic Chemistry and over 25 years of industry experience, he leads international teams in corrosion prevention and chemical management and has established himself as a recognized authority on corrosion inhibitor development. Throughout his career at Clariant and other industry leaders, Dr. Obeyesekere has pioneered green corrosion inhibitor technologies and established multiple integrity laboratories. His expertise extends to major CAPEX projects, providing critical technical support from design through commissioning. A distinguished industry leader, he has authored over 85 scientific publications and patents, and received prestigious recognitions, including the 2017 NACE Distinguished Service Award and 2021 NACE-AMPP Follow Award. Dr. Obeyesekere continues to shape industry standards through his chairmanship of AMPP's Standard Committee 13 and various NACE technical groups.