Importance and Classification of Oil Casings

Oil casings are critical steel pipes used to support the walls of oil and gas wells, ensuring the stability of the wellbore during drilling and after completion. Their primary role is to maintain the integrity of the wellbore, prevent wall collapse, and ensure the proper circulation of drilling fluids. The number and layers of casings used in each well vary based on the drilling depth and geological conditions. Once installed, casings require cementing to secure their position and, due to their one-time-use nature, cannot be reused. Casings account for over 70% of the total consumption of well pipes.

Classification of Casings

Based on their usage, oil casings can be classified into the following types:

1. Conductor Pipe: Positioned at the wellhead, it supports drilling equipment and protects subsequent casings from surface effects.
2. Surface Casing: Protects the upper part of the well from surface layers, preventing the influx of groundwater or other formations.
3. Intermediate Casing: Provides additional support to the wellbore and isolates pressure differences between different formations.
4. Production Casing: Provides the final support for the wellbore and is directly involved in the oil production process.

Types of Oil Tubing

Oil-specific pipes are primarily used for drilling and transporting oil and gas, including:

1. Production Tubing: Used to transport oil and gas from the bottom of the well to the surface.
2. Casing: Supports the wellbore and ensures the normal drilling and completion processes.
3. Drill Pipe: Connects the drill bit to the drilling equipment, transmitting drilling power.

Requirements and Standards for Oil Casings

Given the complex and variable conditions underground, oil casings must meet the following requirements:

• Strength Requirements: Casings must possess high strength to withstand the pressure and stress of the formations. Various steel grades are used, including J55, K55, N80, L80, C90, T95, P110, Q125, V150, etc. Different grades are suited for varying depths and environmental conditions.
• Corrosion Resistance: In corrosive environments, casings must have adequate resistance to corrosion.
• Collapse Resistance: In complex geological conditions, casings need to have good resistance to collapse to prevent wellbore failure.

Importance of Oil Tubing in the Oil Industry

The oil industry relies heavily on oil tubing, with significant implications for cost and efficiency. The importance is reflected in several aspects:

1. Large Quantity and High Cost: The consumption of well pipes is substantial, and the costs are high. For example, drilling 1 meter of depth requires approximately 62 kg of oil pipes, including 48 kg of casings, 10 kg of production tubing, 3 kg of drill pipes, and 0.5 kg of other pipes. Reducing usage and costs presents a significant economic potential.
2. Impact on Drilling Techniques: The mechanical properties and environmental performance of oil pipes directly affect the adoption of advanced techniques and enhanced production efficiency.
3. Safety and Reliability: Failures in oil pipes can lead to substantial economic losses, making their safety and reliability crucial for the oil industry.

In summary, oil casings play a vital role in oil well drilling, with their quality and performance directly impacting the efficiency and economic benefits of the entire drilling process.