Casing consumption accounts for more than 70% of total well pipe consumption.The domestic casing shall be of variable length according to SY/T6194-96, the range of which shall be 8-13 m. However, casing not shorter than 6 m may be supplied, the number of which shall not exceed 20%. The internal and external surfaces of the casing shall not have folding, hairline, delamination, cracks, rolling folds and knots. These defects shall be completely removed to a depth of not more than 12.5% of the nominal wall thickness. The development trend of oil fields will be from land to shoal and from shallow sea to deep sea, coupled with deeper and deeper drilling depths and increasingly complex drilling working conditions, the requirements for oil casing are bound to become higher and higher.
