Application Of Titanium Alloy in Petroleum and Natural Gas Exploration & Development--II
1) Titanium Alloy Oil Sleeve
Most of the natural gas resources in China are sulfur-bearing gas fields, such as Tarim Basin in Xinjiang and Sichuan Basin, which are high in sulfur. The development of highly corrosive oil and gas fields has become a major problem facing the oil and gas industry. Many years of research have been carried out on the corrosion prevention of pipes in oil and gas fields with high H2S and CO2 content domestic and abroad. There are three kinds of corrosion prevention measures: adding corrosion inhibitor, anticorrosive coating and corrosion resistant pipes. The first two ways can play an anticorrosion role to a certain extent, but they can not solve the anticorrosion of long-term service under high temperature and pressure conditions. Therefore, the selection of high quality corrosion resistant materials for pipe has become a leading trend.
There are two main types of corrosion-resistant metal pipes: nickel-based alloys and titanium alloys. At present, nickel-based alloy is widely used, but nickel-based alloy pipe also has some defects, such as complex processing technology, high material cost and easily damage on the surface of pipe. Moreover, China is one of the countries with relatively deficient laterite nickel resources. The national laterite nickel reserves only account for 9.6% of the total nickel resources, and the domestic laterite nickel has a low grade and high mining cost, which means that China has no competitiveness in laterite nickel ore. Therefore, reliance on nickel-based alloys is detrimental to the strategic development of oil and gas in the long term. China is rich in titanium resources, and its ilmenite reserves reach 200 million tons, accounting for 28% of the global reserves, ranking first in the world. Titanium alloys have been used in high sulfur environment due to their excellent corrosion resistance in recent years. Especially when the working conditions are harsh and the content of Cl- and H2S is high, general stainless steel or even nickel-based alloy will corrode. After years of research and development, the titanium alloy material corresponding to ordinary steel has been formed for oil casing. The mechanical properties of titanium alloy tubing are similar to those of nickel-based alloy tubing, and the joint strength meets the requirements of ISO10400 for P110 steel grade.
2) Offshore Drilling Platform Parts, Risers
The requirement of offshore drilling platform is higher than that of land drilling platform. As early as the 1990s, foreign countries have applied titanium alloy to all aspects of offshore drilling platform. The Headway semi-submersible floating rig in Norway, part of the North Sea field, has used titanium as a riser, reducing the overall system mass by 50%, reducing riser lift by 63%t, eliminating the need for huge flexible joints, and reducing system costs by 40%. It is expected to have a service life of 25 years.
In additional, heat exchangers used in cooling systems on offshore RIGS use titanium tubular coolers; Cast titanium pump body and titanium alloy impeller are used in various types of pumps (such as deep well pumps and centrifugal pumps). Various valves and other pipe fittings are also made of titanium to reduce maintenance work.
