CASING AND TUBING

Casing and tubing strings are the main parts of the well construction. All wells drilled for the purpose of oil or gas production (or injecting materials into underground formations) must be cased with material with sufficient strength and functionality.Oil country tubular goods (OCTG) is a family of seamless rolled products consisting of drill pipe, casing and tubing subjected to loading conditions according to their specific application.

In oilfield tubing and casings, thread profiles are designed and manufactured in order to provide superior hydraulic seals between the equipment and pipes. There are several types of Casing Threads used; they include:

Buttress Thread– This type of thread profile is used in pipelines and wellbore tools. It is also used in liner tubular and well casings. The profile of the threading is usually in square cut shape. When the thread comes in contact with the mating thread, a hydraulic seal is created through interference fit which allows the buttress-threaded equipment to lock firmly.

Round Thread – This thread profile is made for the tools and components used in slickline operations. It is also known as a knuckle thread. It is robust and can cause minimal wear and tear by dirt and other impurities inside the wellbore because of its round shape. The Round Thread profile is prepared as per API tubing grades. Round threads can be further divided into two types, i.e., Long Round Thread Profile and Short Round Thread Profile.

PRODUCT SPECIFICATION

SPECIFICATION

Category: ERW, HFW or SMLS

Standards: API Spec 5CT, GB/T 19830​

Steel Grade: H40, J55, K55, N80

THREADING

Casing Thread is the thread profile that is found on casing joints and all casing tools. Casing threads are designed as per API specifications. The thread profiles on well casing can be of various types as below. Some of the advanced Casing Threads incorporate a gas seal.

STC (Short Thread Coupled)
BTC (Buttress Thread Coupled)
LTC (Long Thread Coupled)

CASING COUPLING

API Coupling refers to the steel couplings that used in connecting casing pipe and tubing. Also known by OCTG coupling, it is usually manufactured in seamless type, material grade same with the pipe body (API 5CT K55/J55, N80, L80, P110 etc), same PSL or providing higher grades than requested. Same heat treatment also applicable, except there is an special requirements. A casing coupling has internal threads (female threadform) machined to match the external threads (male threadform) of the long joints of casing. The two joints of casing are threaded into opposite ends of the casing coupling. 

Steel Grade: H-40, J-55, K-55, C-75, L-80, N-80, C-95, AS-95, P-110, L80-13CR

SPECIFICATION OF TUBING 油管尺寸、单位重量

代号外径壁厚内径单位长度重量钢级
 DNO.DW.TI.DWeightSteel Grade
 mmmmmmkg/mH40J55N80-1
 23/860.324.2451.845.86
  4.8350.666.61
  6.4547.428.57  
 27/873.025.5162.009.17
  7.0159.0011.41  
 31/288.95.4977.9211.29
  6.4576.0013.12 
  7.3474.2214.76
 4101.65.7490.1213.57
  6.6588.3015.57 
 41/2114.36.88100.5418.23 
  8.5697.1822.32

SPECIFICATION OF CASING PIPE 套管尺寸、单位重量 API SPEC 5CT

Labels O.D. mmW.T.mmWeight (kg/m)Nominal Linear Mass T&CSteel Grade 
代号 外径壁厚单重 单位长度名义重量 钢级  
12    (带螺纹和接箍)(kg/m)H40J55
K55
N80-1
41/29.5114.305.2114.02 14.14   
 10.5 5.6915.24 15.63    
 11.6 6.3516.91 17.26   
511.5127.005.5916.74 17.11    
 13 6.4319.12 19.35    
 15 7.5222.16 22.32    
51/214139.706.2020.41 20.83   
 15.5 6.9822.85 23.07    
 17 7.7225.13 25.30    
65/820168.287.3229.06 29.76   
 24 8.9435.13 35.72   
717177.805.8724.89 25.30    
 20 6.9129.12 29.76   
 23 8.0533.70 34.23   
 26 9.1938.21 38.69    
75/824193.687.6234.96 35.72    
 26.4 8.3338.08 39.29   
85/824219.086.7135.14 35.72    
 28 7.7240.24 41.67    
 32 8.9446.33 47.62   
 36 10.1652.35 53.57    
95/832.3244.487.9246.20 48.07    
 36 8.9451.93 53.57   
 40 10.0357.99 59.53    
103/432.75273.057.0946.50 48.74    
 40.5 8.8957.91 60.27   
 45.5 10.1665.87 67.71    
 51 11.4373.75 75.90    
113/442298.458.4660.50 62.50    
 47 9.5367.83 69.94    
 54 11.0578.32 80.36    
   12.4287.60 89.29    
133/848339.728.3868.48 71.43    
 54.5 9.6578.55 81.10    
 61 10.9288.55 90.78    

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