I. Overview of API L80 High-Pressure Oil Well Steel Casing
API L80 high-pressure oil well steel casing is a high-strength carbon steel casing that meets the API 5CT standard. It undergoes quenching and tempering treatment to achieve excellent yield strength, tensile strength, and toughness.
This casing is primarily used in medium-depth wells, high-pressure wells, high-temperature wells, and corrosive well sections. It can withstand complex downhole conditions and ensure safe and reliable oil and gas well construction and production.
L80 casing is available in a variety of outer diameters, wall thicknesses, and nominal lengths. PSL-1 or PSL-2 grades and corresponding anti-corrosion treatments are available based on the well environment.
II. API 5CT High-Pressure Oil Well Casing Steel Grade Comparison Table
| Steel Grade | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (%) | PSL Grade | Applicable Well Section | Features |
|---|---|---|---|---|---|---|
| L80 | 552–655 | 655–758 | ≥12 | PSL-1 / PSL-2 | Medium-deep wells, high-pressure wells, corrosive sections | High strength, good toughness, suitable for most deep wells and acidic environments |
| P110 | 758–861 | 861–965 | ≥10 | PSL-1 / PSL-2 | Deep wells, high-pressure high-temperature wells | High-strength steel grade, strong pressure-bearing capacity, suitable for high-temperature high-pressure wells |
| Q125 | ≥862 | ≥965 | ≥9 | PSL-2 | Ultra-deep wells, high-pressure wells | Ultra-high-strength steel grade, suitable for extreme deep wells or special engineering applications |
Comparison Notes
(1) Strength Increment: L80 < P110 < Q125. High-strength steel grades can withstand higher well pressures and temperatures.
(2) Applicable Well Sections: The higher the steel grade, the deeper the applicable well section and the greater the pressure.
(3) PSL Grade: L80 and P110 can choose PSL-1 or PSL-2. Q125 usually only uses PSL-2 to ensure strict quality control.
(4) Procurement Recommendations: Select the appropriate steel grade based on the well depth, well pressure, temperature, and corrosive environment to avoid cost waste or safety risks caused by too high or too low a grade.
III. Chemical Composition and Mechanical Properties of API L80 High-Pressure Oil Well Steel Casing
| Parameter Category | Parameter Name | Value Range |
|---|---|---|
| Chemical Composition | Carbon (C) | 0.17–0.25% |
| Manganese (Mn) | 0.30–0.90% | |
| Sulfur (S) | ≤0.035% | |
| Phosphorus (P) | ≤0.035% | |
| Chromium (Cr) | 0.30–0.60% | |
| Nickel (Ni) | 0.30–0.50% | |
| Molybdenum (Mo) | 0.15–0.30% | |
| Mechanical Properties | Yield Strength (σy) | 552–655 MPa |
| Tensile Strength (σb) | 655–758 MPa | |
| Elongation (δ5) | ≥12% | |
| Impact Toughness (KV) | ≥34 J (Room Temperature) | |
| Elastic Modulus (E) | 2.06×10⁵ MPa | |
| Hardness (HB) | ≤248 | |
| Compressive Strength | Calculated based on wall thickness and diameter | |
| Ductility | Good, suitable for high-pressure well sections | |
| Corrosion Resistance | Medium; acid wells require corrosion protection | |
| High-Temperature Performance | Suitable for long-term use below 150°C | |
| PSL Grade | PSL-1 / PSL-2 | |
IV. API 5CT L80/P110/Q125 High-Pressure Oil Well Casing Purchasing Guide
i. Steel grade selection
L80: Suitable for medium-deep wells, high-pressure wells, and acidic or corrosive well sections. It offers moderate strength and a high cost-effectiveness.
P110: Suitable for deep wells, high-pressure, and high-temperature wells. It offers strong pressure-bearing capacity and is suitable for critical well sections.
Q125: Ultra-high strength, suitable for ultra-deep wells, high-pressure, high-temperature wells, or sections with extreme operating conditions. PSL-2 is typically used.
Procurement Recommendation: Select the steel grade based on well depth, well pressure, temperature, and corrosive environment to ensure a balance between safety and cost-effectiveness.
ii. PSL Level Selection
PSL-1: Basic grade, suitable for conventional high-pressure well sections, with lower cost.
PSL-2: Chemical composition, mechanical properties, and quality control are more stringent, suitable for high-risk well sections.
Purchasing Recommendation: PSL-2 is recommended for critical well sections or extreme operating conditions to reduce construction and production risks.
iii. Size and length
Outer diameter (OD): 114.3–355.6 mm, with customizable larger diameters available depending on well sections.
Wall thickness (WT): 6–15 mm, calculated based on downhole pressure and load requirements.
Nominal lengths: R1: 4.88–7.62 m; R2: 7.62–10.36 m; R3: 10.36–14.63 m.
Purchasing advice: Select length and wall thickness based on well depth, installation equipment, and transportation conditions. Avoid lengths that are too long or too short, which may cause installation difficulties.
iv. Thread and end processing
Thread types: STC/LTC/BTC, ensuring compatibility with wellhead equipment.
End protection: A sleeve protects the threads to prevent shipping damage.
Purchasing advice: Require suppliers to provide detailed thread machining accuracy and protective measures to ensure a reliable seal.
v. Anti-corrosion and surface treatment
Corrosion Protection Type: External Anti-Rust Oil/FBE/3PE
Application Environment: Anti-Rust Oil is suitable for shallow wells or general environments; FBE or 3PE is recommended for medium-deep wells or acidic environments.
Purchasing Recommendation: Select the type of corrosion protection based on downhole corrosion conditions to extend the service life of the casing.
vi. Testing and quality control
Required inspection reports: MTC (chemical composition, mechanical properties, heat treatment records), dimensions, thread inspection, hydrostatic testing, and nondestructive testing.
Procurement advice: Ensure suppliers provide complete inspection reports to avoid substandard products entering the mine.
vii. Supplier selection
Qualifications: API 5CT and ISO 9001 quality system certification.
Capabilities: Production capacity, inventory, delivery time, and after-sales service.
Purchasing Recommendation: Prioritize certified manufacturers to ensure timely delivery and consistent quality.
viii. Transportation and storage
Packaging: Bundled, with end sleeves to protect threads.
Protection: Rust-resistant, impact-resistant, and moisture-resistant.
Purchasing Recommendation: Verify packaging and protective measures before shipping, and inspect the sleeves on-site to ensure they are in good condition.
