Application Of Titanium Materials in Oil Drilling And Production
In recent years, in order to improve crude oil recovery, reduce oil and gas field production costs, and extend the development life of oil and gas fields, there are more and more complex wells, such as large displacement wells, short radius wells, and horizontal wells with side drilling by opening windows in old wells. Conventional drill pipes have encountered some difficult problems when used in these complex wells. For example, in ultra-short radius horizontal wells, the wellbore curvature is very small (<18m), which causes conventional drill pipes to produce large alternating stress. Alternating stress causes drill pipe fatigue fractures from time to time, causing significant losses to oil fields. To solve these problems, foreign countries have begun to start with new materials and develop titanium alloy drill pipes, aluminum alloy drill pipes, composite drill pipes, etc. to replace conventional drill pipes.
1.Higher strength and stronger operating capacity
The laboratory has confirmed that when the cyclic stress is at 30000psi-40000psi, the fatigue life of titanium is 10 times that of ordinary steel. The elastic coefficient of titanium alloy pipes is about 16.5msi, which is more elastic than steel drill pipes and is more suitable for high curvature well sections. At present, titanium alloy drill pipes with good economic efficiency have been produced. The pipe body made of Ti-6Al-4V is upset at both ends and welded to tool joints at both ends. The size of the titanium pipe body meets the API standard and the length range is 2 or 3 specified in the API standard. In order to reduce the manufacturing cost, the tool joint is made of steel, the joint thread is run-in after the make-up and make-out buckle, and the outer diameter of the joint is welded with a wear-resistant belt. Titanium alloy drill pipes are also used in ultra-deep wells and large-displacement wells. Due to the low density of titanium alloy, it can reduce the load of the big hook by 30%, reduce the torque by 30-40%, significantly improve the tension margin and safety factor of the drilling tool, and improve the ability to handle complex accidents.
In daily environment, the service life of titanium alloy drill pipe is 10 times that of conventional steel drill pipe of the same specification; in corrosive environment, it is 100 times that of conventional steel drill pipe. In addition to drill pipes, offshore oil platform pillars, heat exchangers, pumps, valves, etc. are widely used in oil production and refining fields. For example, the North Sea oilfield drilling platform in the United States uses 100 titanium heat exchangers; the Heidrum project in Norway uses the world's first titanium high-pressure riser shaft.
2.More corrosion-resistant and longer service life
For offshore oil production platforms, the corrosion of structural parts caused by biological contamination is quite severe. It often makes traditional metal-made equipment "half dead", but the surface of titanium has a naturally formed, dense, inert, rust-resistant, and corrosion-resistant oxide film, which can easily resist the corrosion of seawater, sulfuric acid, and petrochemicals without additional anti-corrosion treatment. Titanium alloy parts can help oil drilling enter deeper waters and deeper oil wells, including higher temperatures and production environments with severe corrosion (i.e., high salt).
Most of China's natural gas resources are sulfur-containing gas fields, such as the Tarim Basin in Xinjiang and the Sichuan Basin, which are high-sulfur gas fields. The corrosion protection of pipes in oil and gas fields with high H2S2 and C2O2 content and long-term service under high temperature and high pressure conditions are difficult problems in the development of oil and gas. At present, the selection of high-quality corrosion-resistant materials as pipes has become a dominant trend. Titanium alloys are used in high-sulfur environments due to their excellent pitting resistance, especially in harsh working conditions, where the Cl and H2S content is high, and general stainless steel and even nickel-based alloys are corroded.
3. Lighter and more flexible to operate
Although titanium alloy rods are more powerful than steel rods, they are also lighter, with the weight of the same volume being almost half that of steel. Therefore, the drilling torque can be reduced by nearly 50%, and the corresponding load of the top drive on the ground is smaller (PS: smaller force, deeper and more stable drilling), and the equipment is not so easy to break. Therefore, titanium rods are strong and lighter, which can save more effort, fuel, and equipment.
In the future, the global demand for titanium alloy oil pipes with higher strength and stronger corrosion resistance is very urgent. Major domestic steel pipe manufacturing companies and research institutes are actively carrying out research and development work. It is expected that titanium used in the field of oil drilling and transportation is expected to become a large application market for titanium materials.
