CCUS-Based CO₂ Water-Free Fracturing and Enhanced Oil Recovery Technology: Cladding Integration for Industrial Application

1. Definition and Technical Principles

The CO₂ water-free fracturing and enhanced oil recovery (EOR) technology system under the Carbon Capture, Utilization, and Storage (CCUS) framework represents a next-generation approach to hydrocarbon extraction that eliminates conventional water-based fracturing fluids in favor of supercritical or subcritical carbon dioxide as the primary fracturing agent. In this process, CO₂ is injected directly into the formation at pressures exceeding its critical point (approximately 7.38 MPa and 31.1 °C), where it transitions into a supercritical fluid state exhibiting both gas-like diffusivity and liquid-like density. This supercritical CO₂ acts simultaneously as a fracturing fluid, a solvent for heavy hydrocarbons, and a displacement agent that enhances oil recovery by reducing interfacial tension between the reservoir oil and the injected fluid.

The fundamental principle relies on three coupled mechanisms: (1) hydraulic fracturing through high-pressure CO₂ injection creating fracture networks within the reservoir rock; (2) solvent interaction where supercritical CO₂ dissolves lighter components from crude oil, reducing its viscosity and improving mobility; and (3) miscible displacement where CO₂ mixes with residual oil to drive it toward production wells. Unlike conventional water-based hydraulic fracturing, the CO₂ water-free system eliminates issues related to formation damage from water-sensitive clays, reduces the environmental footprint of flowback water management, and provides inherent carbon sequestration through permanent CO₂ retention in the subsurface.

For cladding technology providers, this technology creates critical demand for corrosion-resistant and pressure-rated piping systems, wellhead equipment, and surface facilities that must withstand prolonged exposure to supercritical CO₂ — a highly aggressive medium, particularly in the presence of trace moisture, chlorides, or organic acids. The metallurgical integrity of clad components becomes paramount under the unique thermodynamic conditions encountered in CCUS-EOR operations.

2. Category and Business Positioning

Within the operational framework of Cladding Technology Shanxi Co., Ltd., the CCUS-based CO₂ water-free fracturing and oil displacement technology system design falls under the category of industry-specific technology integration and qualification development. This entry represents the company's strategic positioning at the intersection of traditional metallurgical fabrication expertise and emerging low-carbon energy technologies. The business positioning encompasses three primary dimensions:

Material Solutions Provider: Supplying qualified clad pipe, clad plate, and weld-overlay components designed for CO₂ service environments, where carbonic acid corrosion, hydrogen-induced cracking, and cyclic thermal/mechanical loading demand specialized alloy combinations.
Technical Partnership: Engaging directly with CCUS project developers, EOR operators, and engineering firms to provide metallurgical consultation, material selection guidance, and qualification support for CO₂-specific applications.
Qualification and Certification: Building proprietary WPS (Welding Procedure Specifications) and PQR (Procedure Qualification Records) databases for CO₂ service environments, creating competitive differentiation and entry barriers in the CCUS market segment.

This positioning aligns with China's national strategy for CCUS deployment and the oil and gas industry's transition toward lower-carbon extraction methodologies, positioning the company as an essential supplier in the supply chain for CCUS-EOR projects.

3. Technical Purpose and Value

3.1 Primary Technical Purpose

The integration of cladding technology into the CO₂ water-free fracturing and EOR technology system serves the following technical purposes:

Corrosion Protection: Providing barrier protection against CO₂ corrosion (sweet corrosion) in supercritical and subcritical CO₂ environments, where the formation of iron carbonate (Fe₃C) scales and localized pitting can compromise structural integrity.
Pressure Containment: Ensuring the structural integrity of pressure vessels, piping spools, and wellhead assemblies that must withstand injection pressures typically ranging from 25 to 70 MPa for supercritical CO₂ fracturing operations.
Hydrogen Damage Resistance: Mitigating hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) mechanisms that are accelerated in CO₂-containing environments, particularly when trace H₂S or water is present.
Thermal Cycling Durability: Maintaining metallurgical integrity through repeated thermal cycles associated with CO₂ injection (cooling) and oil production (heating) operations.

3.2 Quantifiable Value

Extension of asset life in CO₂ service by 3–5 times compared to uncladded carbon steel alternatives
Reduction of unplanned shutdown events due to corrosion-related failures
Compliance with regulatory requirements for CO₂ storage integrity under national and international standards
Cost avoidance through elimination of full-alloy construction while maintaining equivalent corrosion resistance

4. Key Process and Implementation Points

4.1 Material Selection for CO₂ Service

Material selection for CCUS-EOR applications requires careful consideration of the specific thermodynamic conditions, fluid composition, and mechanical requirements of the intended application. The following table summarizes recommended clad combinations for various CO₂ service scenarios:

Application Zone	Base Material	Clad/Overlay Alloy	Minimum Clad Thickness	Key Design Consideration
Injection Piping (Supercritical CO₂)	Q345R / API 5L X65	304L / 316L / 904L	3.0 mm	Carbonic acid corrosion resistance, pressure rating
Wellhead Components	API 5CT P-110	316L / Alloy 6	2.0 mm	High-pressure containment, HIC resistance
Surface Separation Equipment	Q235B / Q345B	316L / 2205 Duplex	2.5 mm	Chloride stress corrosion resistance (if brine present)
Storage Tanks (CO₂)	Q345R	304L / 316L	2.0 mm	Long-term CO₂ containment integrity
Injection Valves (Internal Parts)	ASTM A182 F91	316L / Alloy C-276	1.5 mm (overlay)	Erosion-corrosion, rapid cycling

4.2 Weld Overlay Implementation for CO₂ Service

TIG and MIG weld overlay procedures for CO₂ service applications require specific modifications to standard procedures to ensure adequate protection against carbonic acid corrosion and hydrogen damage:

Shielding Gas Composition: Use of pure argon (99.99% purity minimum) or argon-helium mixtures to minimize oxygen and moisture ingress; nitrogen-containing mixtures are prohibited for 316L and 904L overlays in CO₂ service due to potential embrittlement effects.
Interpass Temperature Control: Maintain interpass temperatures below 150 °C for austenitic stainless overlays to prevent sensitization and chromium carbide precipitation at grain boundaries.
Post-Weld Heat Treatment: Solution annealing at 1050–1100 °C followed by rapid quench for critical components; stress relief at 300 °C maximum for components where sensitization is not a concern.
Weld Metal Chemistry Control: Maintain carbon content below 0.030% (304L/316L grade) or below 0.020% (304LN/316LN grade) to maximize resistance to intergranular corrosion.
Multi-Pass Strategy: Employ a minimum of two overlay passes for critical CO₂ service applications, with the first pass providing metallurgical bonding and the second pass providing a clean, defect-free surface with controlled microstructure.

4.3 Hydraulic Explosive Bonding for CO₂ Service Clad Plate

Hydraulic explosive bonding (HEB) provides a cold-welding mechanism for producing clad plate where the absence of thermal input preserves the full mechanical properties of both base and cladding materials. For CO₂ service applications:

The bonding interface achieves metallurgical continuity without heat-affected zones, ensuring that the corrosion resistance of the clad layer is not compromised by thermal degradation.
Minimum clad thickness of 2.0 mm is recommended for supercritical CO₂ environments to provide adequate diffusion barrier protection.
Post-bonding inspection must include 100% ultrasonic testing (UT) for interface integrity per ASTM E2197 or equivalent, supplemented by macrographic examination per ASTM A280.
The bonded interface must demonstrate no separation under applied stresses equivalent to 1.5 times the design pressure of the intended service.

4.4 Explosion Welding for CO₂ Service Clad Pipe

Explosion welding (EW) produces clad pipe with a metallurgical bond between the base steel pipe and the corrosion-resistant overlay, suitable for injection piping and wellhead applications in CO₂-EOR operations:

Typical explosion welding parameters for CO₂ service pipe: detonation velocity of 2500–3500 m/s, interface wave amplitude of 0.05–0.15 mm, and collision velocity of 300–400 m/s.
Post-explosion cold rolling or hydroforming to achieve final dimensional tolerances (typically ±0.5 mm for outer diameter, ±0.1 mm for wall thickness).
Interface quality verification through macrographic etching (5% HNO₃ + 5% HF solution) and evaluation per ASTM A280 requirements.
Residual stress assessment through X-ray diffraction or hole-drilling methods, with stress relief treatment applied if residual stresses exceed 50% of the yield strength of the cladding material.

5. Applicable Standards and Acceptance Criteria

5.1 Material and Fabrication Standards

Standard Number	Scope of Application	Relevance to CO₂ Service
ASTM A377	Clad steel plate, sheet, and strip	Material specification for clad plate in CO₂ storage and processing
ASTM A403	Clad steel pipe	Welded clad pipe for CO₂ injection piping systems
ASTM A563	Clad steel forgings	Wellhead components, valves, and flanges for CO₂ service
NACE MR0175/ISO 15156	Materials for H₂S-containing environments	Applicable when CO₂ co-exists with H₂S in formation fluids
API 5CT	Specification for casing and tubing	Base material specification for wellhead and casing components
API 6A	Wellhead and Christmas tree equipment	Design and qualification of wellhead assemblies for CO₂ injection
ASME B31.3	Process piping	Design and construction of CO₂ process piping systems
ASME BPVC VIII Div.1/2	Pressure vessels	Design of CO₂ storage tanks and separators
GB/T 13296	Welded clad steel pipe	Chinese national standard for clad pipe fabrication
GB/T 14976	Seamless steel tubes for mechanical and structural uses	Base pipe specification for explosion-welded clad pipe
NB/T 20305	Nuclear-grade clad materials	Applicable by analogy for high-integrity CO₂ containment applications

5.2 Non-Destructive Testing Acceptance Criteria

Ultrasonic Testing (UT): Interface bond integrity verified per ASTM E2197 with 100% coverage; acceptance criterion of no indications exceeding 3 mm equivalent flat-bottom hole at the clad/base interface.
Visual Testing (VT): Surface quality per ASTM E94, with no cracks, folds, or excessive surface roughness (Ra ≤ 12.5 μm for overlay surfaces in CO₂ service).
Magnetic Particle Testing (MT): Applied to ferromagnetic base material surfaces to detect surface and near-surface discontinuities per ASTM E1444.
Positive Material Identification (PMI): 100% verification of clad/overlay material chemistry per ASTM E1685 (XRF) or ASTM E1922 (LIBS), confirming compliance with specified alloy grade.
Hardness Testing: Vickers hardness measurement across the interface per ASTM E92, with maximum hardness of the cladding material not exceeding 250 HV for 316L or 300 HV for 304L to maintain ductility and crack resistance.

5.3 Performance Verification Standards

Corrosion Testing: Immersion testing in 5% NaCl solution at 60 °C per ASTM G48, with maximum weight loss rate of 0.1 mm/year for the clad surface.
Intergranular Corrosion Testing: ASTM A262 Practice E (oxalic acid) or Practice A (65% boiling HNO₃), with no evidence of intergranular attack.
Pressure Testing: Hydrostatic pressure test at 1.5 times design pressure per ASME B31.3 Section 345.4, with no leakage or permanent deformation.
Impact Testing: Charpy V-notch impact testing per ASTM E23 at minimum service temperature, with minimum absorbed energy of 27 J for base material and 47 J for clad material at the lowest design temperature.

6. Common Risks and Controls

6.1 Carbonic Acid Corrosion (Sweet Corrosion)

Risk Description: In supercritical CO₂ environments, particularly with trace water content, carbonic acid (H₂CO₃) forms and attacks unprotected carbon steel surfaces, leading to uniform thinning, localized pitting, and eventual perforation. The corrosion rate increases significantly above the CO₂ dew point and in the presence of chlorides or sulfides.

Control Measures:

Ensure continuous and defect-free cladding coverage with minimum thickness of 2.0 mm for supercritical CO₂ service
Implement 100% UT inspection of clad interfaces to detect and repair any bond separations
Apply corrosion inhibitor injection upstream of critical equipment as a secondary protection measure
Establish a corrosion monitoring program with electrical resistance probes and coupon testing at intervals not exceeding 6 months

6.2 Hydrogen-Induced Cracking (HIC)

Risk Description: Atomic hydrogen generated by CO₂ corrosion reactions can accumulate at inclusions, laminations, and microstructural boundaries within the base material, leading to blistering, stepwise cracking, and catastrophic failure. This is particularly critical for high-strength steels (HYS) with yield strength above 517 MPa.

Control Measures:

Specify base materials meeting NACE MR0175/ISO 15156 Part 2 requirements for HIC resistance
Implement strict control of sulfur content in base material (≤ 0.005% for HIC-sensitive applications)
Apply hydrogen blister resistance testing per ASTM G123 for critical base materials
Ensure proper weld overlay procedures that do not introduce hydrogen into the base material (controlled arc length, dry electrodes, proper shielding)

6.3 Clad/Overlay Interface Degradation

Risk Description: Thermal cycling, cyclic loading, and long-term exposure to CO₂ can lead to progressive degradation of the metallurgical bond at the clad/base interface, manifesting as microcracking, interfacial oxidation, or delamination.

Control Measures:

Design for maximum interpass temperature control during weld overlay to minimize interfacial reaction zones
Specify clad materials with thermal expansion coefficients closely matched to the base material (e.g., 316L with Q345R)
Implement periodic in-service UT monitoring of clad interfaces at critical locations
Design for thermal expansion accommodation through proper joint design and flexibility analysis

6.4 Hydrogen Embrittlement of Clad Material

Risk Description: Supercritical CO₂ can act as a hydrogen carrier, and atomic hydrogen permeation through the clad layer into the base material can lead to hydrogen embrittlement of the cladding material itself, particularly for high-strength overlay alloys.

Control Measures:

Limit overlay hardness to ≤ 250 HV for austenitic stainless steels in CO₂ service
Avoid martensitic or precipitation-hardened overlay alloys unless specifically qualified for hydrogen service
Implement post-weld dehydrogenation treatment (200–250 °C for 2–4 hours) for critical components
Conduct slow-strain-rate testing per ASTM G178 in simulated CO₂ environments for qualification of overlay procedures

7. Application Scenarios Across Company Technology Routes

7.1 TIG/MIG Weld Overlay Route

The TIG/MIG weld overlay technology route is the primary method for applying corrosion-resistant coatings to existing piping, equipment, and components in CCUS-EOR applications. Specific scenarios include:

Injection Piping Retrofit: Application of 316L or 904L TIG weld overlay to existing carbon steel injection piping to extend service life in supercritical CO₂ environments. Typical overlay thickness: 2.0–4.0 mm in multiple passes with 100% RT/UT inspection of each pass.
Valve Body Overlay: MIG weld overlay of Alloy 6 or Alloy C-276 on valve body internal cavities that experience rapid CO₂ flow and erosion-corrosion. Post-overlay machining to final dimensions with surface finish Ra ≤ 6.3 μm.
Flange Face Overlay: TIG weld overlay of 316L on flange sealing surfaces to ensure leak-tight joints in CO₂ service where gasket materials may be compromised by supercritical CO₂ exposure.
Repair and Restoration: Application of overlay welds to repair localized corrosion damage on in-service CO₂ piping and equipment, restoring original wall thickness and corrosion protection.

For CCUS applications, the company has developed and qualified WPS procedures specifically addressing the unique metallurgical challenges of CO₂ service, including controlled dilution rates (≤ 15% base material dilution into the first overlay pass), optimized travel speeds to minimize heat input, and post-weld treatment protocols to eliminate residual hydrogen.

7.2 Hydraulic Explosive Bonding Route

The hydraulic explosive bonding technology route produces clad plate for large-area applications in CCUS-EOR facilities. Specific scenarios include:

CO₂ Storage Tank Fabrication: Production of 304L/Q345R clad plate for above-ground and underground CO₂ storage tanks, providing both structural integrity and long-term corrosion protection against carbonic acid attack.
Heat Exchanger Fabrication: Manufacture of 316L/Q345B clad plate for CO₂/oil heat exchangers where thermal cycling and corrosion resistance are simultaneously required.
Process Vessel Fabrication: Supply of 2205/Q345R clad plate for CO₂-water separation vessels where both chloride resistance and pressure containment are critical.
Platform and Structural Components: Production of clad structural plate for CO₂ injection platform structures exposed to marine and CO₂-containing atmospheres.

The hydraulic explosive bonding process offers particular advantages for CCUS applications due to the complete absence of thermal input, ensuring that the full corrosion resistance of the austenitic cladding material is preserved. The cold-welding mechanism produces a diffusion-free interface with superior long-term stability under cyclic loading conditions encountered in CO₂ injection operations.

7.3 Explosion Welding Route

The explosion welding technology route produces clad pipe and clad fittings for high-pressure CO₂ injection and production systems. Specific scenarios include:

High-Pressure Injection Piping: Production of 316L/API 5L X70 explosion-welded clad pipe for supercritical CO₂ injection lines operating at 40–70 MPa, requiring both high structural strength and superior corrosion resistance.
Wellhead and Casing Components: Fabrication of explosion-welded clad casing and tubing for CO₂ injection wells, providing corrosion protection at the wellbore while maintaining mechanical integrity under high downhole pressures and temperatures.
Separator and Scrubber Internals: Production of explosion-welded clad pipe for CO₂/oil/gas separation systems where continuous exposure to supercritical CO₂ and formation water creates aggressive corrosion conditions.
CO₂ Pipeline Systems: Supply of explosion-welded clad pipe for dedicated CO₂ transport pipelines connecting capture facilities to injection sites, requiring long-term integrity over decades of service.

For CCUS-EOR applications, explosion welding provides a unique combination of metallurgical bond strength (typically exceeding 200 MPa shear strength at the interface), full preservation of clad material properties, and the ability to produce complex geometries including elbows, tees, and reducers in a single operation. The process is particularly well-suited for long-run pipe production required for CO₂ pipeline networks.

8. Contribution to Qualification Building, Product Delivery, and Customer Value

8.1 Qualification Building

The development of CCUS-specific technical capabilities contributes directly to the company's qualification portfolio in the following ways:

WPS/PQR Database Expansion: Qualification of new welding procedure specifications specifically designed for CO₂ service environments, including controlled dilution procedures, specialized post-weld treatments, and CO₂-specific NDT acceptance criteria.
Material Qualification: Development of proprietary material qualification packages demonstrating the performance of specific clad combinations under simulated supercritical CO₂ conditions, including long-term immersion testing and cyclic loading tests.
Standards Compliance: Achievement of compliance with emerging CCUS-specific standards and industry guidelines, including API 6A amendments for CO₂ service, NACE SP0106 for CO₂ corrosion control, and GB/T standards for CCUS facility design.
Third-Party Certification: Obtaining certification from recognized bodies (such as TUV, DNV, or CNAS-accredited laboratories) for CO₂ service materials and fabrication procedures, creating a competitive advantage in the CCUS market.

8.2 Product Delivery Enhancement

The CCUS technology integration enhances the company's product delivery capabilities through:

Specialized Product Lines: Development of dedicated product lines for CCUS applications, including CO₂-rated clad pipe, CO₂-rated clad plate, and CO₂-rated weld overlay services, each with specific qualification documentation and performance guarantees.
Accelerated Delivery: Pre-qualification of materials, procedures, and inspection protocols for CCUS applications enables faster project execution and reduced lead times compared to ad-hoc qualification of each project.
Integrated Solutions: Ability to provide complete material solutions combining clad pipe, clad plate, weld overlay services, and technical consultation under a single contract, simplifying the procurement process for CCUS project developers.
Traceability and Documentation: Comprehensive documentation packages including material certifications, WPS/PQR records, NDT reports, and performance test results that meet the rigorous documentation requirements of CCUS project owners and regulators.

8.3 Customer Value Creation

The CCUS technology capability creates measurable value for customers through:

Risk Mitigation: Reduction of corrosion-related failure risk in CO₂ service through qualified materials and proven fabrication procedures, protecting customer assets and ensuring operational continuity.
Cost Optimization: Elimination of the need for full-alloy construction by providing clad solutions that achieve equivalent corrosion protection at 40–60% lower material cost, while maintaining full structural integrity.
Regulatory Compliance: Assurance that delivered products meet all applicable standards and regulatory requirements for CCUS operations, reducing customer exposure to regulatory penalties and project delays.
Lifetime Cost Reduction: Extension of asset service life through superior corrosion protection, reducing total cost of ownership through deferred replacement, reduced maintenance, and elimination of unplanned shutdowns.
Technical Partnership: Provision of metallurgical expertise and application engineering support that enables customers to optimize material selection, minimize over-design, and achieve the best balance between performance and cost.

9. Implementation Roadmap and Strategic Recommendations

9.1 Short-Term Actions (0–12 Months)

Complete qualification of 316L/Q345R and 904L/API 5L X65 clad combinations for supercritical CO₂ service through accelerated corrosion testing and mechanical property verification.
Develop and document proprietary WPS procedures for CO₂ service weld overlay with full PQR support, including CO₂-specific NDT acceptance criteria.
Establish partnerships with CCUS project developers and EOR operators to identify specific material requirements and project timelines.
Conduct literature review and technical study on the long-term performance of clad materials in supercritical CO₂ environments, including published case studies and laboratory data.

9.2 Medium-Term Actions (1–3 Years)

Obtain third-party certification for CO₂ service materials and fabrication procedures from recognized international bodies.
Establish a dedicated CCUS product line with standardized specifications, qualification packages, and delivery documentation.
Develop a corrosion monitoring and asset integrity management service for CCUS facilities, providing ongoing value beyond initial product delivery.
Contribute to industry standardization efforts for CCUS-specific material requirements and fabrication practices through participation in API, NACE, and GB standards committees.

9.3 Long-Term Strategic Positioning (3–5 Years)

Position the company as the leading clad materials supplier for CCUS-EOR applications in China and potentially in international markets.
Develop proprietary technology for advanced clad materials specifically designed for extreme CO₂ service conditions (high temperature, high pressure, high chloride content).
Establish a technical center for CCUS materials research and development, conducting fundamental research on clad material performance in supercritical CO₂ environments.
Expand product portfolio to include digital asset management solutions for CCUS facilities, integrating material performance data with real-time monitoring systems.

10. Conclusion

The integration of cladding technology into the CCUS-based CO₂ water-free fracturing and enhanced oil recovery technology system represents a strategic opportunity for Cladding Technology Shanxi Co., Ltd. to expand its market presence in the rapidly growing low-carbon energy sector. The company's established capabilities in TIG/MIG weld overlay, hydraulic explosive bonding, and explosion welding provide the technical foundation necessary to address the unique material challenges of CO₂ service environments. Through systematic qualification building, standards compliance, and customer-focused value creation, the company can position itself as an essential supplier in the CCUS supply chain, contributing to both the commercial success of CCUS-EOR projects and the broader transition toward lower-carbon energy production.

The technical challenges associated with CO₂ service — including carbonic acid corrosion, hydrogen-induced cracking, thermal cycling, and cyclic mechanical loading — demand rigorous material selection, precise fabrication control, and comprehensive quality assurance. The company's existing expertise in metallurgical bonding, weld overlay qualification, and non-destructive testing provides a strong foundation for addressing these challenges, while the development of CCUS-specific procedures and qualification packages will create sustainable competitive advantages in this emerging market segment.