Author: [Bruce Zhou]
Affiliation: [Jota Machinery Composites Material Prepreg Solution]
Corresponding Author: [jotamachinery@gmail.com]
Published : April 08 , 2026

RTP aromatic crude ASP compatibility

Abstract

Reinforced thermoplastic pipe (RTP) has transitioned from a corrosion-resistant alternative to carbon steel into a viable solution for chemically aggressive oilfield environments. This study examines the suitability of unbonded RTP systems—comprising a bimodal HDPE liner, helically wrapped glass-fibre reinforcement, and HDPE outer jacket—for transporting crude oil containing aromatic hydrocarbons and alkaline fluids used in enhanced oil recovery (ASP EOR).

Laboratory immersion testing, full-scale pressurised pipe evaluation, and long-term field cut-out analysis are combined to assess material stability, structural integrity, and fitting performance. Results show that temperature governs mechanical degradation more strongly than aromatic concentration, while moderate plasticisation of the liner does not translate into meaningful loss of pipe strength.

For ASP environments, both the polymer liner and electroless nickel coated fittings demonstrate strong resistance under controlled conditions, with field data confirming long-term integrity. The findings define a practical service envelope for RTP and shift engineering focus from polymer degradation toward temperature management and fitting performance under flow conditions.

Keywords

Reinforced thermoplastic pipe, RTP chemical compatibility, aromatic crude oil, ASP EOR, HDPE liner, composite pipeline, oilfield transport, corrosion-resistant pipeline

1. Introduction

The adoption of RTP in oil and gas has historically been driven by one factor: corrosion elimination. However, as deployment expands, engineers are no longer asking whether RTP resists corrosion—they are asking whether it can survive chemically aggressive production fluids under real operating conditions.

Crude oils containing aromatic and cyclo-aliphatic hydrocarbons, along with alkaline surfactant polymer (ASP) fluids used in enhanced oil recovery, represent two of the more demanding service environments. These fluids challenge polymer stability, reinforcement integrity, and metallic fittings in different ways.

This paper addresses a practical question faced in field development:

Can unbonded RTP systems reliably operate in aromatic-rich crude and ASP EOR conditions without compromising structural performance?

The analysis is grounded not only in laboratory data but also in field-returned pipe sections, providing a direct link between controlled testing and operational reality.

2. Literature Review

Early RTP qualification frameworks, such as those established under API RP 15S, focused on pressure capacity and long-term regression behavior. These approaches provided a baseline for structural integrity but offered limited insight into chemical compatibility under complex fluid exposure.

Subsequent studies expanded understanding in three key areas:

  • Mechanical behavior: Research demonstrated that unbonded RTP exhibits non-linear deformation due to reinforcement geometry and load transfer characteristics.
  • Field validation: Long-term installations in water injection systems confirmed durability in corrosive environments.
  • Material evolution: More recent work explored RTP suitability for emerging applications such as hydrogen transport.

Despite these advances, a gap remained in understanding how RTP performs when exposed to combined chemical and thermal loading, particularly in aromatic hydrocarbons and alkaline EOR fluids.

The GOEC 2011 study fills this gap by providing both laboratory and field-based evidence of material behavior under these conditions.

3. Methodology

3.1 RTP Construction

The investigated pipe system consists of:

  • Inner liner: bimodal HDPE acting as fluid barrier
  • Reinforcement: continuous glass fibres helically wrapped
  • Outer jacket: HDPE protective layer

The pipe is unbonded, allowing flexibility and spoolable installation but also enabling relative movement between layers.

3.2 Chemical Exposure Testing

Two fluid environments were evaluated:

Aromatic / Cyclo-Aliphatic Hydrocarbons

  • Simulated crude oil with controlled solvent content
  • Exposure at 20°C, 40°C, and 60°C
  • Mechanical properties measured after saturation

ASP EOR Fluids

  • pH range: 11–12.5
  • Alkali concentration: 0.5–1%
  • Surfactant/polymer content: ~0.1%

3.3 Mechanical Evaluation

Testing included:

  • Tensile properties of HDPE liner (yield strength, modulus, elongation)
  • Full-scale pipe burst testing after exposure
  • Pressurised pipe testing under controlled temperature

3.4 Field Validation

A critical component of the study is the analysis of:

  • RTP pipe sections removed after ~5 years of ASP service
  • Visual inspection of liner and reinforcement
  • Residual burst strength testing

3.5 Fitting Corrosion Assessment

Electroless nickel coated carbon steel fittings were evaluated using:

4. Results

4.1 Effect of Aromatic Hydrocarbons

The data shows a clear trend:

  • Temperature has a stronger impact on HDPE properties than solvent concentration
  • At elevated temperature (60°C), mechanical properties converge regardless of solvent content

Practical thresholds were established:

  • Up to 25% aromatics at 20°C
  • Up to 10% at 40°C
  • Up to 5% at 60°C

4.2 Structural Integrity After Exposure

Full-scale pipe testing revealed:

  • Burst pressure remained within expected variability (~100–105% of baseline)
  • No evidence of structural weakening despite liner plasticisation

This confirms that:

moderate changes in liner properties do not directly compromise pipe strength

4.3 Gas Condensate Performance

Exposure to condensate with moderate aromatic content showed:

  • Minor reduction in liner yield strength
  • No significant impact on burst performance

This supports RTP use in ambient-temperature condensate transport.

4.4 ASP EOR Performance

Laboratory and field results align:

  • Minimal change in liner mechanical properties
  • No visible degradation after extended exposure
  • Field-returned pipe maintained ~98.6% of original burst strength

Reinforcement layers showed:

  • No fibre damage
  • No loss of tensile capacity

4.5 Fitting Performance

Corrosion testing indicated:

However:

performance is dependent on low flow velocity and minimal erosion

5. Discussion

5.1 Temperature as the Primary Design Driver

The findings confirm that temperature—not fluid composition—is the dominant factor affecting HDPE behavior.

For engineering decisions, this shifts the focus from:

  • “What is the fluid composition?”

to:

  • “What is the actual liner temperature during operation?”

5.2 Polymer Behavior vs System Performance

A key insight is the distinction between:

  • material-level changes (plasticisation)
  • system-level performance (burst strength)

The study shows that RTP can tolerate moderate liner property changes without compromising structural integrity.

5.3 The Real System Weak Point

The results suggest that long-term reliability is more likely governed by:

  • fitting performance under flow conditions
  • erosion and solids impact
  • installation quality

rather than liner degradation.

5.4 Implications for Offshore Applications

For offshore and onshore deployment, RTP is well suited for:

  • produced water and injection lines
  • ASP EOR transport systems
  • moderate-temperature crude and condensate

Less suitable applications include:

  • high-temperature multiphase flow
  • erosive or sand-laden streams
  • dynamic riser systems

5.5 Integration with Broader RTP Knowledge

When combined with prior studies:

  • mechanical modeling explains deformation behavior
  • field data confirms durability
  • chemical testing defines service limits

Together, they form a complete engineering framework for RTP deployment.

6. Conclusion

This study demonstrates that unbonded RTP systems can operate reliably in aromatic crude oil and ASP EOR environments within defined temperature-dependent limits.

Key conclusions:

  • Temperature is the dominant factor influencing HDPE performance
  • Aromatic exposure within defined limits does not compromise structural integrity
  • ASP fluids have minimal impact on liner and reinforcement over multi-year service
  • Fitting performance is condition-dependent and must be carefully evaluated

The broader engineering takeaway is:

RTP design should prioritise temperature control and fitting performance rather than focusing solely on polymer compatibility.

This perspective aligns more closely with field experience and provides a more practical basis for deployment decisions in oil and gas projects.

References

  1. Parvez, M., Sakr, A., Yeats, B., Weller, M. (2011). Suitability of Reinforced Thermoplastic Pipe in Crude Oil Containing Aromatic Solvents and ASP Fluids. GOEC.
  2. API RP 15S – Spoolable Reinforced Plastic Line Pipe
  3. ASTM D2992 – Pressure Testing of Plastic Pipe
  4. CSA Z662 – Oil and Gas Pipeline Systems
  5. Industry field studies on RTP deployment in corrosive environments
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