Despite our efforts to promote renewable resources, oil and gas will continue to be the main force of energy in the coming decades. Since most of the traditional resources available have been exhausted, it has to be developed to make it more difficult to exploit oil and gas fields. In order to meet the rapid growth of oil and gas demand, more advanced collection methods must be used in existing oil and gas fields. The era of easy exploitation of oil and gas has ended.
In the past few decades, the share of oil and gas production in offshore oil exploration platforms has increased substantially, and the rapid development of ultra-deep water exploitation is expected to maintain its growth momentum in the future. The difficulty of oil and gas exploration is increasing because the working environment is becoming more and more demanding, for example, higher temperature and pressure, and high acid environment of CO2 (high hydrogen sulfide content). Under these harsh conditions, in order to ensure the normal production of oil and gas, and more importantly, safe production, advanced technology, good equipment and high-performance materials must be available.
This is where corrosion-resistant alloys come in because they are more responsive to increasingly stringent mining and production requirements. As a result, the demand for alloy steel, stainless steel and nickel alloys in the upstream oil and gas industry has increased significantly, and this trend will continue. Types of Corrosion Resistant Alloys Used in the Oil and Gas Industry The most representative corrosion resistant alloys are stainless steel and nickel alloys. In addition to typical corrosion resistant alloys, special alloy steels are also widely used in the oil and gas industry. Alloy steel and stainless steel account for 95% of the total amount, while nickel alloy accounts for only 5%, but it accounts for 25% of the total value. The demand and choice of corrosion resistant alloys depends on the production/storage environment (classified by importance):
- Corrosive (hydrogen sulfide, carbon dioxide, chloride)
The corrosion engineer calculates the expected annual corrosion rate and then multiplies it by the design life. When the expected amount of corrosion exceeds a certain value, a corrosion-resistant alloy may be used, or carbon steel may be used, but the wall thickness is increased. In addition to the use of an overall corrosion-resistant alloy material, it is also possible to perform corrosion-resistant alloy compounding or surfacing on the surface of carbon steel or alloy steel. Another anti-corrosion measure is chemical inhibitor or cathodic protection.
While safety is the first element, material selection also depends on the calculated life cycle cost. Although the initial investment in corrosion resistant alloys is large, it may be a more economical option over the entire life cycle, which reduces the number of replacements, reduces maintenance, and eliminates the need for chemical inhibitors. The order of selection of steel for oil and gas projects is carbon steel→alloy steel→13Cr martensitic stainless steel→300 series stainless steel→duplex steel (22Cr)→super duplex stainless steel (25Cr)→28Cr (alloy 28)→Ni alloy→titanium alloy. Use carbon steel and alloy steel wherever possible, as they have the lowest cost.
However, as the working environment deteriorates, higher grade materials must be gradually selected, and corrosion resistant alloys are irreplaceable. The most widely used steel grades in the oil and gas industry are described in more detail below:
- Alloy steel: 4145H, 4130, 4140, 4330, 8630, F22
- Martensitic stainless steel: 13Cr, Super13Cr, 410, 420, F6NM
- Austenitic stainless steel: 316, 304, 321, 317L, Nitronic 50/60, 904L254SMO (6Mo)
- Duplex stainless steel: 2205, 2507, LDX2101
- PH steel: 17-4, 15-5, 13-8
- Nickel alloy: 825, 625, 718, 925, alloy 28
- Non-magnetic steel: special chromium manganese austenitic steel
Corrosion-resistant alloys are required for a variety of product types, including 3D forgings, rolling rings, forged and rolled bars, welded and seamless pipes, composite pipes, slabs and strips. Corrosion-resistant alloys are used in the oil and gas industry. Special alloy steels and corrosion-resistant alloys are used in a wide range of applications, especially at sea. They can be used as drill strings, pipes, casings, downhole completions, wellheads, blowout preventers, subsea trees, manifolds, risers, oil pipes, jumpers, umbilicals, valves, pumps, water Processing equipment, etc. The following are some application examples:
- Oriented and horizontal drilling components are forged on a precision rotary forging press using special non-magnetic steel and then machined. The bottom hole assembly includes a drill collar, MWD and LWD tools, a downhole power drill and a drill bit.
- Seamless pipes are used for pipes and casings (OCTG). 13Cr, super duplex stainless steel or nickel alloy can be selected depending on the fluid composition. Need to be cold worked to increase strength.
- The composite welded pipe has low cost and can replace the corrosion resistant alloy pipe, the oil outlet pipe, the conveying pipe and the steel catenary riser. The composite pipe is made of carbon steel mother pipe and corrosion resistant alloy (such as 316L, 825, 625). The composite method has two techniques of metallurgy or mechanical compounding.
- The hose can replace the rigid oil pipe and riser. The skeleton is made of cold rolled coil. Common steel grades are 316L, economical duplex, duplex and super duplex stainless steel.
- Large forgings, such as blowout preventers and subsea trees. Usually made of alloy steel (F22, 8630, 4130), in order to prevent corrosion, the wet zone part is made of nickel alloy surfacing. Small forgings, such as valve bodies, also use duplex stainless steel.
- Large-diameter thin-wall welded pipes are used for LNG pipes (mainly 304L and 316L). The LNG cryogenic transfer line uses Invar (Alloy 36) or 9% nickel steel. Invar can also be used as a film for LNG carriers.
Macro Trends and Driving Forces The application of corrosion resistant alloys in the global oil and gas industry is driven by two completely different forces: the US’s terrestrial shale oil and gas and global offshore oil and gas fields (especially deep water), which are very different, but develop The speed is very fast. Over the past five years, tremendous advances in drilling and completion technology have led to explosive growth in the production of US terrestrial shale gas. The development of horizontal drilling and hydraulic fracturing technology has freed previously unavailable resources and changed the US terrestrial resource market. In less than 10 years, the proportion of horizontal drilling rigs in the United States has increased from 10% to over 60%. In the face of the deformation of the bottom hole equipment plus the corrosive nature of shale gas and high pressure shale oil, the rig must be made of high quality materials.
With the help of many factors, the use of corrosion resistant alloys at sea, especially in the deep sea, has exceeded the demand baseline. The investment in offshore projects will reach 1.2 trillion in 2013-2017, an increase of 57% over the previous five years. Investment in deep sea projects will exceed $800 billion, an increase of 60% over the previous five years. Deep sea project investment mainly comes from two aspects, one is deep sea and ultra deep sea mining in the US Gulf of Mexico, Africa and Brazil; the other is natural gas mining, especially LNG production in Asian land and floating equipment. For new deep-sea and ultra-deep sea development projects, producers face higher reservoir pressures and temperatures, and they are also learning about the experience and lessons of existing deep-sea and ultra-deep-sea development projects. As a result of increased attention to the safety and operational data of existing equipment, major oil companies and large national oil companies require their manufacturing companies to use higher grade materials for subsea equipment.
As wellhead pressures reach 15,000 psi, and even higher, well flow temperatures reach 350 °C, corrosion-induced pollution, including carbon dioxide and hydrogen sulfide, and demand for high-quality materials such as stainless steel and nickel alloys will continue to grow.
Although the rapid development of shale gas has significantly reduced the price of natural gas in the United States, the rapid growth of energy demand in Asian markets (including China, Japan, South Korea and India) and concerns about nuclear energy have led to an increase in LNG prices there. The growth in demand for LNG has prompted a large amount of capital to be invested in new and expanded LNG projects. The new capacity of LNG will reach 200 million t/year from 2013 to 2017. Most of this natural gas comes from offshore platforms, and liquefaction is done on land or on floating installations. Although most LNG projects are currently in shallower waters (within 500m), most offshore LNGs use underwater technology, including long-distance anchors for untreated wells. Many times the gas contains a lot of impurities, so that the steel in contact with the well flow is in a highly corrosive environment. In addition, environmental regulations in Australia and other regions are very strict, equipment must be long-lived, and maintenance-free for life. This requires manufacturers to use high-quality materials, including nickel-alloy composites or integral stainless steel tubes for subsea equipment and pipelines.
Under the dual push of offshore and shale gas mining, the oil and gas industry will increase the use of stainless steel and special steel to meet technical challenges and exploit proven resources. For those companies that are willing to invest time and resources in accordance with the stringent standards of the oil and gas industry, opportunities to expand sales are everywhere.
Source: China Alloy Steel Pipes Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)