Sep 13, 2026Applications & Projects
Oil Casing: Development and Use in Oil and Gas Wells
Oil casing, part of the OCTG family, is the steel pipe that lines an oil or gas well and supports the well wall so the well can operate normally after
Quick answer: Oil casing, part of the OCTG family, is the steel pipe that lines an oil or gas well and supports the well wall so the well can operate normally after drilling. Over roughly two decades, supply in China moved from a standing start to a broad range of API and non-API products, and demand has since shifted from mature eastern fields towards western and offshore acreage.
What Oil Casing Is
Oil casing is used to support the well wall of an oil and gas well to ensure the normal operation of the entire well after the drilling process is complete. Each well uses several casing layers according to drilling depth and geological conditions. Because casing is cemented in place, it differs from tubing and drill pipe in one important respect: it cannot be reused.
From a Standing Start to a Full Product Range
After nearly 20 years of work, oil casing production in China grew from scratch. It moved from low price to high price and from low steel grades to API series products and then to non-API products for special needs, approaching the level of foreign products in both quantity and quality. In market terms, China's OCTG has held a domestic market share above 80 percent and has been a net export product for many years.
The Demand Picture Behind the Growth
In 2011, crude oil production in China reached 204 million tonnes, an increase of 0.32 percent against the same period a year earlier, while natural gas production reached 102.531 billion cubic metres, a year-on-year increase of 6.9 percent and a record high. China remained in a stage of rapid urbanisation and industrialisation, and oil demand was expected to grow at an average annual rate of around 4 percent in the following years. Continued growth in oil demand boosted demand for oil drilling equipment.
Where Demand Is Moving
Inside China, demand for oil casing is no longer concentrated in the eastern region. The development trend of domestic oil and gas fields is shifting from the early mature eastern fields towards western fields and towards offshore fields, and further from land to tidal flats and from shallow seas to deep seas. Drilling depth is increasing, operating conditions are becoming more complex, and the requirements placed on oil casing are therefore bound to rise.
As drilling moves deeper, into tougher formations and further offshore, casing specification stops being a commodity decision and becomes an engineering one.
What This Means for Buyers
Tighter well conditions translate into tighter casing requirements. Buyers should state the steel grade, connection, wall thickness, standard and inspection route on the enquiry. Standard families such as API, ASTM, GB and GOST define ordering and acceptance, and independent inspection can be arranged through SGS, BV, TUV and TUBOSCOPE. SPAI STEEL, as a subsidiary of SP Group founded in 1996, exports steel pipe to more than 100 countries and can confirm the grade and specification that fit a given well.
FAQ
What is oil casing used for?
It supports the well wall of an oil or gas well so the whole well can operate normally once drilling is finished.
How large is China's OCTG market share?
China's OCTG products have held a domestic market share above 80 percent and have been a net export product for many years.
Why are casing requirements rising?
Wells are being drilled deeper in more complex conditions, and development is moving towards western and offshore fields, all of which raise the demands placed on casing.
Which standards govern oil casing?
API, ASTM, GB and GOST are among the standard families that define ordering and acceptance for casing and OCTG products.
Send your well conditions, casing grade, standard and destination port to the SPAI STEEL team for a confirmed recommendation.
