Project Description
Special Thread Connection Oil Casing and Tubing
Detailed Product Description
As oilfield development environments change, deep wells, ultra-deep wells, high-pressure gas wells, thermal recovery wells, extended reach wells, and complex geological structure wells require higher connection strength and sealing performance from oil and tubing casing.
API round-thread connections have low gas-tight sealing performance, with only 60~80% of the pipe body’s connection strength. Although API buttress threads have higher connection strength, their sealing performance is not ideal.
Domestic special thread oil tubing mainly relies on imports, with only a few technically advanced entities engaged in product development and production. Research on foreign special threads began with VAM in the 1960s and has since developed into over 30 companies with more than 100 patented products suitable for drilling and production in various conditions. Special threads account for 22% of the total usage of oil and tubing casing abroad, reaching up to 60% in Europe.
To meet the growing needs of oil and gas fields regarding thread connection strength and sealing performance, we have successfully developed the CB series of special thread connections and collaborated with foreign companies to develop various special thread products suitable for different operating environments. Special thread oil and tubing casing are being used in major domestic oilfields such as Daqing, Jilin, Dagang, Changqing, Southwest, Shengli, and Jidong. Internationally, Rosneft, Lukoil, Ecuadorian National Oil Company, TNK-BP, Colombian National Oil Company, and Venezuelan National Oil Company have all used our products.
Naming Conventions for Special Threads
- CB + Function Code + Series Number: CB stands for CHANGBAO (company name abbreviation).
- Single-lip double-metal gas-tight connection: represented by the first letter of SEAL, “S”.
- API couplingless extreme-line casing: represented by the letters “X”.
- Integral joint tubing: represented by the first letter of INTEGRAL JOINT TUBING, “IJ”.
- Thickened direct-connect type: represented by the first letter of SEMI-FLUSH, “SF”.
- High-torque connection: represented by the first letter of HIGH TORQUE, “HT”.
- High-compression resistance connection: represented by the first letter of HIGH COMPRESSION, “HC”.
- Two-step torque connection: represented by the first letter of TWO-STEP-TORQUE, “TS”.
- Two-step tapered connection: represented by the first letter of TWO-STEP-TAPERED, “TSTA”.
- High-temperature and high-pressure connection: represented by the first letter of HIGH PRESSURE AND HIGH TEMPERATURE, “HP”.
Series numbers use Arabic numerals (1, 2, 3…) to indicate different types within the same function.
Currently developed special thread types include:
- CBS1, CBS2, CBS3 (passed ISO 13679-CAL IV evaluation); CBS1-OV gas-tight opposing thread; CBS3C; CBX; CBIJ; CB-EU-HT; CB-SF; CB-FJ; CBTS.
- Collaborative thread types include Flush-Max, Flash-MaxⅡ/Ⅲ, Super-Max, Super-MaxTS/TS2, MO-EU-PA, MO-CSG-PA, GEOCONN, etc.
Steel Grades Suitable for Products
Special threads are applicable to all steel grades produced by our company.
Features of Independently Developed Special Threads
Features of CBS1 Special Thread Structure Considering the needs of oil and gas well development both domestically and internationally, the CBS1 special thread design features the following characteristics:
- High joint strength — coupling connection.
- High thread connection strength — buttress thread (8 threads per inch for tubing, 5 threads per inch for casing).
- Good gas-tight sealing performance — dual-metal seal structure.
- No vortex or erosion — smooth inner bore transition.
- Good anti-sticking performance — coupling threads and sealing surfaces treated with copper alloy plating.
Application Scope Deep wells, ultra-deep wells, high-pressure gas wells, directional wells, complex geological structure wells requiring high connection strength and sealing performance, and corrosion-resistant wells.
Specifications and Performance Parameters of Conventional CBS1 Gas-Tight Special Thread Oil and Tubing Casing
| Outer Diameter (mm) | Wall Thickness (mm) | Coupling OD (mm) | Loss Length (mm) | Pipe Body Yield Strength (kN) | Coupling Connection Yield Strength (kN) | Internal Yield Pressure (MPa) | Collapse Strength (MPa) | Gas-Tight Performance (MPa) |
|---|---|---|---|---|---|---|---|---|
| 73.03 | 5.51 | 88.90 | 66.1 | 886 | 886 | 100.1 | 100.3 | 73.6/73.3 |
| 139.7 | 9.17 | 153.70 | 120.3 | 2853 | 2853 | 87.2 | 76.6 | 85.8/64.4 |
Note: Gas-tight performance column A refers to the test results according to API RP 5C5 section 3.3.4 (final internal pressure cycle and thermal cycle tests, thermal cycle temperature 177°C). Column B refers to the test results according to TGRC1 (gas-tight test under bending and tensile conditions, dogleg severity 20°/30m, composite stress reaching 85% of the pipe body yield stress).
Actual Performance and Application CB110S-13Cr special thread oil and tubing casing has been used in carbon dioxide-corrosive gas wells in China National Petroleum Corporation’s oil fields. The actual product performance is as follows:
| Outer Diameter (mm) | Wall Thickness (mm) | Steel Grade | Yield Strength (MPa) | Collapse Strength (MPa) | Akv (T-10-0) | Hardness (HRC) | Thread Type |
|---|---|---|---|---|---|---|---|
| 73.03 | 5.51 | CB110S-13Cr | 823 | 986 | 120 | ≤32 | CBS1 |
| 139.7 | 9.17 | 860 | 979 |
Operating Environment: Formation pressure 41.4-43.2 MPa, formation temperature 122-140°C, average CO2 content 26.77%, formation water total salinity 1215.4-13775.3 mg/L, chloride ion content 287.8-3438.9 mg/L.
CBS2 Special Thread Structure Features
- Metal-to-Metal Seal: Specific short cone metal-to-metal seal design optimizes and ensures reliable sealing.
- Torque Shoulder: Designed to control the coupling position accurately and reduce circumferential stress in the connection area.
- Thread Design: 3° angle on the load-bearing side of the thread profile eliminates slippage during tension and provides good connection strength. Multiple pitch designs enhance the speed of connection. More engaged threads optimize stress distribution.
- Smooth Inner Connection: Continuous smooth inner bore without shoulders reduces turbulence.
- Coupling Design: Optimized coupling dimensions ensure efficient connection while minimizing size.
- Surface Treatment: Copper alloy plating on sealing faces, torque shoulders, and thread profiles enhances anti-sticking performance.
Special Options
- Special Gap Coupling: Available in smaller outer diameter couplings.
- Special Chamfer Coupling: Available with different chamfer angles.
Benefits Suitable for deep wells, horizontal wells, extended reach wells, high-pressure gas wells, and stress-corrosion resistant wells.
CBS3 Special Thread Structure Features
- Design Characteristics: Negative angle (-3°) on the bearing surface, increased gap on the male thread peak, reduced gap on the engagement side.
- Benefits: Superior tensile strength, excellent anti-sticking performance, uniform sealant distribution, excellent mechanical properties under compression and tension.
- Mechanical Performance: 100% equivalent to the pipe body in tensile strength, collapse resistance, and internal pressure resistance.
- Sealing Performance: No gas leakage under composite loads.
- Make-Up/Uncoupling: Easy to make-up and uncouple without sticking after ten cycles.
Collaboratively Developed Integ-max Special Thread
- Co-developed with Japan’s Metalone: Used primarily for oil production in abandoned wells and difficult drilling operations such as those in Russia’s third-largest oil field TNK-BP.
- Design Features:
- Size range: 60.32-114.3 mm.
- Thickened end — thickened external ends ensure connection strength.
- Integral connection — seamless direct connection without couplings.
- Dual-shoulder seal — dual-shoulder design resists over-torque and ensures sealing.
- Non-API standard buttress threads with 45-degree lead-in angle and 2-degree bearing face.
- High bending and anti-sticking capability.
- Phosphating or sandblasting surface treatment on both male and female ends.
Application Scope Directional wells, complex geological structure wells requiring high connection strength and sealing performance; abandoned well rehabilitation; deep wells, ultra-deep wells, gas wells.
Performance Characteristics of Integ-max
| Pipe Body Diameter (mm) | Nominal Weight (Kg/m) | Wall Thickness (mm) | Collapse Strength (MPa) | Internal Yield Pressure (MPa) | Minimum Yield Load (ton) |
|---|---|---|---|---|---|
| 114.3 | 18.9 | 6.91 | 36.5 | 47.2 | 76.0 |
| 102.0 | 16.4 | 6.65 | 45.4 | 60.7 | 48.7 |
| 89.0 | 13.9 | 6.45 | 51.0 | 72.7 | 39.8 |