Exploration and innovative practice of new application fields of oil casing technology
Date:2025-03-25View:116Tags:Epoxy pipe,Coated pipe,API casing
Oil Country Tubular Goods (OCTG) is the core equipment for oil and gas extraction, mainly used for wellbore support, fluid transportation and completion operations. With the technological innovation of the energy industry and the global low-carbon transformation, the application fields of oil casing are constantly expanding, extending from traditional oil and gas extraction to emerging fields such as shale gas development, geothermal energy, carbon sequestration (CCUS), and hydrogen energy storage and transportation. This article will deeply analyze the key technological breakthroughs and market prospects of oil casing in these new scenarios.
1. Shale gas and unconventional oil and gas development: the demand for high-strength and corrosion-resistant oil casing has surged
1. Application of shale gas horizontal wells
Shale gas extraction relies on large-scale hydraulic fracturing technology, which puts higher requirements on the mechanical properties and fatigue resistance of oil casing:
High-grade steel materials: high-strength steel grades such as P110 and Q125 are widely used to withstand high pressure (above 10,000 psi) and frequent stress changes in fracturing operations.
Special thread design: VAM TOP, FOX and other airtight threads are used to ensure the integrity of the wellbore and prevent methane leakage.
Case: 13Cr martensitic stainless steel oil casing is commonly used in shale gas wells in the Permian Basin of the United States, which is resistant to hydrogen sulfide corrosion and has a service life of 30%.
2. Ultra-deep wells and high temperature and high pressure (HPHT) environment
In ultra-deep wells over 8,000 meters, oil casing needs to withstand high temperatures and ultra-high pressures above 200°C:
Nickel-based alloy casing: such as Inconel 718 alloy, used in deepwater projects in the Gulf of Mexico, with excellent resistance to hydrogen sulfide stress cracking (SSC).
Composite coating technology: ceramic or polytetrafluoroethylene (PTFE) sprayed on the inner wall to reduce friction resistance and prevent scaling.
2. Geothermal energy development: high temperature resistance and resistance to geothermal fluid corrosion
Geothermal well temperatures can reach above 300°C, and geothermal fluids contain high concentrations of chloride ions, carbon dioxide and other corrosive media, and traditional carbon steel oil casing is prone to failure.
Key technological breakthroughs:
Duplex stainless steel (2205/2507): It has both strength and corrosion resistance. The Hellisheiði geothermal power plant in Iceland uses 2507 duplex steel casing with a service life of 20 years.
Titanium alloy oil casing: Experiments at Kyushu University in Japan show that the corrosion rate of titanium alloy in acidic geothermal environment is only 1/50 of that of carbon steel, but the cost is higher and it is suitable for demonstration projects.
Market prospects: Global geothermal installed capacity is expected to reach 24GW in 2030, and the demand for oil casing will increase by 12% annually.
3. Carbon Sequestration (CCUS): Ensure the safety of long-term CO2 storage
Carbon capture and storage (CCUS) requires CO2 to be injected into underground depleted oil and gas reservoirs or saline aquifers. The oil casing needs to solve the following challenges:
1. Supercritical CO2 corrosion
CO2 is in a supercritical state (>31℃, 7.38MPa) under high pressure, and combines with water to form carbonic acid, and the corrosion rate is far higher than that of conventional working conditions:
13Cr/15Cr martensitic stainless steel: The Norwegian Sleipner project verified its CO2 corrosion resistance, but the wellbore humidity needs to be strictly controlled.
Non-metallic composite materials: such as glass fiber reinforced epoxy resin casing, the US Department of Energy funded experiments show that it can completely block CO2 penetration.
2. Sealing reliability
Use metal-to-metal seal threads, such as Tenaris' Blue series, to ensure the sealing of the storage well for a hundred years.
4. Hydrogen energy storage and transportation: Oil casing converted into underground hydrogen storage carrier
The large-scale storage and transportation of green hydrogen needs to rely on underground salt caverns or depleted gas fields. The existing oil casing technology can be adapted and modified:
1. Solution to hydrogen embrittlement
Hydrogen can easily cause hydrogen embrittlement of steel (Hydrogen Embrittlement), and traditional N80 steel is not suitable:
Low alloy steel + corrosion inhibitor: Germany's KBB company developed the HYTECH series casing, which reduces hydrogen permeability by adding copper/vanadium elements.
Lined polymer coating: such as PTFE lining, the UK HyStorPor project has verified its effectiveness.
2. Salt cavern hydrogen storage dedicated casing
Salt layer creep may squeeze the wellbore, requiring high-anti-collapse casing (such as V&M's VM-H2 series, with a 40% increase in anti-collapse strength).
5. Deep-sea and polar oil and gas: extreme environmental adaptability
1. Arctic low temperature environment
Low-temperature tough steel: For example, X80 steel still maintains impact toughness at -60°C, and is widely used in Russia's Yamal project.
Electrically heated smart casing: Shell is testing electric heating casing in the Canadian Arctic to prevent crude oil from freezing.
2. Deepwater corrosion protection
Seawater corrosion-resistant alloys: such as AL-6XN super austenitic stainless steel, used in Brazilian subsalt oil fields.
Cathodic protection + coating: BP uses "zinc anode + epoxy coating" dual protection in the deepwater area of the Gulf of Mexico.
VI. Future trends: intelligence and greening
Smart oil casing: embedded with fiber optic sensors to monitor stress, temperature and corrosion status in real time (such as Schlumberger's IntelliPipe).
Low-carbon manufacturing: electric arc furnace short-process steelmaking (CO2 emissions per ton of steel reduced by 60%) + hydrogen energy iron reduction technology (such as the HYBRIT project).
