Steel well casing pipe is a large-diameter pipe that plays a role in fixing the walls or wellbore of oil and natural gas wells. Oil casing plays a very important role in the oil field production process. The successful extraction of oil and gas is closely related to the strength performance of OCTG casing.
Factors affecting the strength of steel well casing pipe
Steel casing pipe plays a role in isolating formation pressure in oil wells to prevent well wall collapse. The oil casing working underground mainly bears axial tension and internal and external pressure. There are two main factors that affect its strength: one is the geometric size and accuracy of the components; the other is external interference forces.
Currently, there are two methods used for safety calculation of petroleum casing: one is to assume that the damage of the casing is caused by elastic instability; the other is to assume that the damage of the casing is caused by insufficient yield strength of the material. From the perspective of engineering mechanics, strength and structural stability are two different concepts, and their structural damage properties are still non-ideal systems. Any kind of structure, whether it is an ideal system or a non-ideal system, when it is subjected to external loads, there are two internal relationships, one is the relationship between external force and structural deformation, and the other is the relationship between external force and internal stress of the structure.
Solving the relationship between external force and internal stress is a strength issue. The limiting factor of the structural load-bearing capacity is the size of the stress, and its safety is to ensure that the stress does not exceed a certain allowable value. The stability problem generally involves studying the relationship between the external force and deformation of the structure, and finding a specific extreme value of the external force during the deformation process. This extreme value is the critical load for structural instability, regardless of the size of the internal stress. Calculation and analysis show that the studied casing damage form is a strength problem. Based on this, it is concluded that the dimensional errors produced during the production process of the casing will increase or decrease the strength of the casing to a certain extent.
In addition, there are other factors that affect the strength of steel well casing pipe
(1)Material
There are many materials for steel well casing pipe, the most common ones are carbon steel, alloy steel and stainless steel. Since oil casing pipe plays a role in supporting the well wall during the oil extraction process, there is a high demand for the strength of the material. Ordinary carbon steel material cannot meet this requirement to a certain extent because it is easily corroded by harsh environments such as seawater. Therefore, in order to ensure the strength of oil casing, it is very important to choose appropriate raw materials.
(2)Outer diameter
The outer diameter of the steel pipe refers to the length from the outer surface of the steel pipe to the inner wall of the pipe, usually expressed in millimeters (mm). For example, a steel pipe with a diameter of 50 mm has an outer diameter of 50 mm. The outer diameter is one of the most basic dimensional parameters of steel pipes, which directly affects the use range and load-bearing capacity of steel pipes. The thicker the outer diameter, the stronger the load-bearing capacity of the steel well casing pipe.
Factors affecting the strength of steel well casing pipe
Steel casing pipe plays a role in isolating formation pressure in oil wells to prevent well wall collapse. The oil casing working underground mainly bears axial tension and internal and external pressure. There are two main factors that affect its strength: one is the geometric size and accuracy of the components; the other is external interference forces.
Currently, there are two methods used for safety calculation of petroleum casing: one is to assume that the damage of the casing is caused by elastic instability; the other is to assume that the damage of the casing is caused by insufficient yield strength of the material. From the perspective of engineering mechanics, strength and structural stability are two different concepts, and their structural damage properties are still non-ideal systems. Any kind of structure, whether it is an ideal system or a non-ideal system, when it is subjected to external loads, there are two internal relationships, one is the relationship between external force and structural deformation, and the other is the relationship between external force and internal stress of the structure.
Solving the relationship between external force and internal stress is a strength issue. The limiting factor of the structural load-bearing capacity is the size of the stress, and its safety is to ensure that the stress does not exceed a certain allowable value. The stability problem generally involves studying the relationship between the external force and deformation of the structure, and finding a specific extreme value of the external force during the deformation process. This extreme value is the critical load for structural instability, regardless of the size of the internal stress. Calculation and analysis show that the studied casing damage form is a strength problem. Based on this, it is concluded that the dimensional errors produced during the production process of the casing will increase or decrease the strength of the casing to a certain extent.
In addition, there are other factors that affect the strength of steel well casing pipe
(1)Material
There are many materials for steel well casing pipe, the most common ones are carbon steel, alloy steel and stainless steel. Since oil casing pipe plays a role in supporting the well wall during the oil extraction process, there is a high demand for the strength of the material. Ordinary carbon steel material cannot meet this requirement to a certain extent because it is easily corroded by harsh environments such as seawater. Therefore, in order to ensure the strength of oil casing, it is very important to choose appropriate raw materials.
(2)Outer diameter
The outer diameter of the steel pipe refers to the length from the outer surface of the steel pipe to the inner wall of the pipe, usually expressed in millimeters (mm). For example, a steel pipe with a diameter of 50 mm has an outer diameter of 50 mm. The outer diameter is one of the most basic dimensional parameters of steel pipes, which directly affects the use range and load-bearing capacity of steel pipes. The thicker the outer diameter, the stronger the load-bearing capacity of the steel well casing pipe.
