Oil Casing & Tubing Product Introduction

1. General Overview

2. Oil Casing

2.1 Function

• Support wellbore and prevent collapse.

• Isolate formations with different pressure and fluid to avoid interlayer channeling.

• Seal high-pressure, corrosive strata and ensure operational safety.

2.2 Classification (Running Sequence)

1. Conductor Casing: Outermost pipe, fixes wellhead and protects shallow formation.

2. Surface Casing: Seals shallow freshwater layers.

3. Intermediate Casing: Isolates complex, high-pressure and sour formations.

4. Production Casing: Final string for oil & gas production.

2.3 Common Sizes

Main outer diameters: 5-1/2", 7", 9-5/8", 13-3/8"Wall thickness: 6.0 mm ~ 22.2 mm

2.4 Steel Grades

• Regular: J55, K55, N80 (for shallow & low-pressure wells)

• Medium grade: L80, C90, T95 (for medium-deep & mildly sour wells)

• High grade: P110, Q125, V150 (for deep, ultra-deep, high-temperature & high-pressure wells)

• Corrosion resistant: L80-13Cr, P110SS (for H₂S & CO₂ sour wells)

2.5 Thread Connections

Standard API Threads

• STC (Short Round Thread)

• LTC (Long Round Thread)

• BTC (Buttress Thread)

3. Oil Tubing

3.1 Function

Convey oil and gas from reservoir to surface after well completion. Withstand high internal pressure, fluid erosion, corrosion and alternating load during service.

3.2 Classification (End Type)

• NU (Non-Upset): Uniform pipe body, cost-effective for shallow wells.

• EU (External Upset): Reinforced pipe end, higher tensile & torque strength, main type for medium-deep wells.

• Integral Joint: No coupling, superior gas tightness and fatigue resistance for high-pressure & sour wells.

3.3 Common Sizes

Main outer diameters: 2-7/8", 3-1/2", 4"Wall thickness: 5.0 mm ~ 12.0 mm

3.4 Steel Grades

Regular: J55, N80High performance: L80, P110, L80-13Cr, P110SS

3.5 Thread Connections

API standard threads and above-mentioned T-type premium connections are both available for selection.