Material types and selection of oil casing pipe

Meaning and function of oil casing pipe:

Oil casing pipe is a kind of pipeline equipment commonly used in the oil and gas industry. It is used for drilling, production, transportation and control of fluid in the well. It is usually a long steel pipe installed in oil wells or natural gas wells. It is used to maintain the integrity of the wellbore structure, control fluid transportation and isolate the fluids of different formations in the well. Oil casing has important functions such as protecting the wellbore, controlling the fluid in the well, isolating the formation and realizing oil and gas production. There are mainly the following types and material selections of oil casing.

Material types and selection of oil casing pipe:

1. Carbon steel casing
Carbon steel casing (including seamless casing and erw casing) is one of the common oil casing materials. It has good strength and corrosion resistance and is suitable for most oil well environments. The advantages of carbon steel casing include low cost, easy processing and installation.

2. Stainless steel casing
Stainless steel casing is mainly composed of elements such as chromium and nickel and has good corrosion resistance and oxidation resistance. It is suitable for some oil well environments with special requirements, such as offshore oil fields or hydrogen-sulfur oil and gas wells.

3. Chrome alloy casing
Chrome alloy casing is a high temperature and corrosion resistant material, suitable for high temperature, high pressure or corrosive formation environment. It has good strength and durability and can withstand harsh working conditions for a long time.

4. Nickel alloy casing
Nickel alloy casing is also a commonly used oil casing material, which has excellent corrosion resistance and high temperature performance. Nickel alloy casing is suitable for acidic, alkaline or sulfur-containing formation environments to prevent corrosion and damage.

5. Titanium alloy casing
Titanium alloy casing is a lightweight and high-strength material with good corrosion resistance and high temperature resistance. It is suitable for some oil well environments with high weight requirements, which can reduce the load of equipment and improve work efficiency.

6. FRP casing
FRP casing is a casing made of glass fiber and resin composite material with excellent corrosion resistance and mechanical properties. It is suitable for some special environments such as marine salt wells or acidic oil wells.

7. Ceramic casing
Ceramic casing has high corrosion resistance and wear resistance and is suitable for formation environments. It can resist the erosion of casing by factors such as high temperature, high pressure, acidity and wear.

8. Composite casing

Composite casing is a casing composed of a combination of multiple materials, which can be designed and manufactured according to specific needs. It can take into account various performance requirements such as strength, corrosion resistance, temperature resistance, etc.

Type of drilling casing pipe:

The drilling environment often requires several layers of casing to achieve the expected total well depth. Each layer of casing can be divided into the following categories according to its function:

(1) Conductor. The outermost layer of the well, its main function is to reinforce the well wall and prevent the surface gravel layer and unbonded rock from falling into the well.

(2) Structural pipe. Located between the conductor and the surface pipe, the purpose of this layer of casing includes solving the problem of leakage or well collapse and avoiding the problem of shallow gas well kick as much as possible.

(3) Surface casing. The purpose of the lower surface casing is multiple, including isolating the freshwater layer, preventing collapse and leakage, isolating the weak layer section that cannot withstand the back pressure applied by controlling the well kick, providing conditions for installing the blowout preventer, and supporting the weight of all layers of casing that are smaller than the surface casing.

(4) Intermediate casing. The main purpose is that high-pressure layers will be encountered during drilling, and high-density drilling fluid is needed to control the abnormally high pressure. Shallow and weak formations must be protected to prevent leakage or stuck drill. In some special cases, intermediate casing is also used to isolate salt layers or expansive and easily collapsed shale layers.

(5) Liner. The liner has the same function as the intermediate casing. The liner extends from the bottom of the well upward into the intermediate casing, but does not extend to the ground. In order to save money, the liner does not need to extend the pipe string to the ground but can still achieve the purpose of controlling pressure and fracture gradient.

(6) Production casing. Also known as reservoir casing. The function of this pipe string is to separate the production layer from other formations, form a working wellbore with a given diameter that can be lowered to the production layer, and protect the production oil pipe and equipment.

(7) Back-up pipe string. The liner is also often used as part of the production casing, instead of running another pipe string from the ground to the production layer. The liner can be returned to the ground from the top of the liner with an appropriate amount of pipe.

Conclusion:
The material selection of oil casing pipe should be determined according to the characteristics and requirements of the oil well environment. Different materials have different advantages and applicable scopes. Engineers need to make choices based on actual conditions to ensure the stability and reliability of the casing in the oil well. The material selection of oil casing is also constantly developing and innovating to meet the increasingly complex needs of oil and gas extraction.

Hunan Standard Steel Co., Ltd is a leading manufacturer and distributor of seamless steel pipe, welded steel pipe, OCTG products (casing pipe and drill pipe), hollow section (square tube and retangular tube) and pipe fittings (such as pipe flange,elbow,reducer). For more, contact: info@hu-steel.com

Read more: Carbon steel vs Stainless steel