Whether dry FRP oil-oil casings (usually referring to non-metallic casings/pipes made of fiberglass-reinforced thermosetting resin, with no liquid layer inside, used for oil wells or oil transport in an 'oil-oil' casing structure) are suitable for high-temperature oil depends on the specific temperature range, resin system, and medium conditions. It can't be generalized, but there is a clear upper temperature limit, so caution is needed in high-temperature oil scenarios.  

1.Core limitation: material temperature resistance  

The temperature resistance of FRP is mainly determined by the matrix resin. Common systems are as follows:  

- Unsaturated polyester resin (UP): long-term temperature resistance generally ≤ 80~100°C, short-term (a few hours) can reach about 120°C;  

- Vinyl ester resin (VE): long-term temperature resistance ~100~120°C, high-quality modified grades can reach 130~140°C;  

- Epoxy resin (EP): general long-term temperature resistance ≤ 120°C, high-temperature types (e.g., phenolic epoxy) can reach 150~180°C, but brittleness increases and cost is high;  

- Phenolic resin (PF): theoretically can withstand over 200°C, but poor processability and low toughness make it rarely used in oil casings.  

The typical design long-term use temperature for conventional dry FRP oil casings is ≤ 120°C. Above this temperature, the resin accelerates aging and the crosslinked structure is damaged, leading to a sharp drop in strength and increased leakage risk.  

2.Risks of transporting high-temperature oil  

If the oil temperature exceeds the limits mentioned above (e.g., heavy oil thermal recovery, high-temperature crude (>120°C), steam-assisted conditions):  

- Mechanical property decline: FRP tensile/compressive strength decreases nonlinearly with temperature, prone to creep and instability at high temperatures;  

- Medium compatibility deterioration: light components, sulfides, naphthenic acids in high-temperature oil can accelerate resin swelling and corrosion;  

- Interface failure: fiber-resin interface can de-bond at high temperatures, causing delamination or pipe rupture;  

- Standards and certification limits: API, SY/T, and other oil casing standards usually specify the temperature range for FRP casings, and exceeding it is not compliant.  

3.Recommended applicable scenarios  

Suitable: transportation of crude oil, refined oil, water injection at normal to medium temperatures (≤100~120°C), especially useful in corrosive environments (e.g., high HS/CO content);  

Not suitable: high-temperature oil (>120°C hot oil, thermal heavy oil steam injection pipes), or long-term over-temperature conditions. For transporting high-temperature media, metal casings with insulation layers or special high-temperature resin-based composites should be used.  

Conclusion  

Dry FRP oil-oil casings are not suitable for transporting oil above the resin’s temperature limit (usually >120°C is not recommended). Their advantage lies in medium to low-temperature corrosive conditions. When selecting, carefully check the resin grade, manufacturer-provided temperature curves, and medium compatibility reports.