Special pipes for oil and natural gas drilling and transportation are collectively referred to as petroleum geological pipes. Among them, the geological pipe is specially used for geological exploration and is the main tool for exploring underground resources. Geological pipe includes geological drill pipe, core pipe, casing, and drill collar. Oil pipes include oil (natural gas) well pipes and oil (gas) pipelines. According to the application, oil well pipe can be divided into three categories: casing, drill pipe (pipe), and oil pipe.
In the process of oil and natural gas drilling, the role of the drill pipe is to drive the drill bit to rotate; to send the mud to the bottom of the well. When drilling, the drill pipe produced by the steel pipe factory is connected to a drill string with a length of several hundred meters or several thousand meters using threaded joints or welding. The drill pipe of a deep well often consists of 3 to 4 drill pipe strings. The role of the casing is to strengthen the well wall. Like the drill pipe, dozens or hundreds of casings are threaded to form a casing string, and a deep well also has 3 to 4 casing strings. Oil pipelines are used to transport crude oil.
Varieties and manufacturing methods of petroleum geological pipes Oil and gas wells are located in different regions, and the service conditions of oil well pipes (environmental temperature, pressure, medium type, well depth, stratum structure, etc.) are also different, and the requirements for the physical and chemical characteristics of pipe materials are also different. same. (See Figure 2) Oil well pipes used in deep well drilling require high strength and crush resistance; oil well pipes working in media containing H2S or CO2 require high-stress corrosion resistance against H2S or CO2; Oil well pipes working in high-pressure require high thread tightness and blast resistance; oil well pipes used in cold regions require good low-temperature toughness.
API standards have clear and strict regulations on the geometric dimensions, steel grades, physical and chemical properties, and manufacturing methods of oil pipes.
The diameter of the geological drilling pipe (rod) is 33.5-89mm, and it is produced with special steel with a yield strength of 500-950MPa; the diameter of the core pipe and casing is 34.5-426mm, and it is produced with special steel with the yield strength of 400-950MPa. Steel production; the diameter of the drill collar is 70-85mm, and it is produced with special steel with a yield strength of 500-950MPa. Different steel grades are selected according to the drilling depth and geological conditions, and the deeper the well, the higher the steel grade selected.
Production process The general production process of petroleum casing is as follows: steelmaking (mostly smelted by pure oxygen top-blown converter or electric furnace)--external refining (ladle powder spraying, vacuum treatment, etc.)--continuous casting--tube billet flaw detection- -Pipe rolling by the rolling mill (continuous rolling mill, skew rolling extension mill, automatic milling mill, periodic milling mill, etc., see hot-rolled seamless pipe mill)--Pipe flaw detection after rolling (magnetic flaw detection, ultrasonic flaw detection, etc. )--Heat treatment (synchronous feeding into the furnace, segmented furnace, induction heating, etc.)--Straightening--Flaw detection--Pipe end threading (using program-controlled or CNC special machine tools)--Screw the coupling, the inner diameter- -Hydrostatic test--length measurement, weighing, spray marking--painting, packaging, storage
The general production process of oil drill pipe is: steelmaking-outside furnace refining-continuous casting-pipe billet flaw detection-pipe rolling unit rolling pipe-pipe flaw detection after rolling-pipe end thickening-heat treatment- Straightening--flaw detection--pipe end processing--welding tool joint--deburring--weld seam heat treatment and processing--weld seam flaw detection--pipe inner coating--spray marking--packing--warehousing
The production process of oil tubing is the same as that of oil drill pipe, but the tool joints are not welded. The production process of geological pipes (casing, drill pipe) is the same as that of oil pipes (casing, drill pipe). To connect the geological pipes produced by the factory (generally about 8m in length) into the well, screw threads are threaded at both ends of the drill pipe, core pipe, casing, and drill collar, and then connected with a coupling. stand up. To ensure that the strength of the rear ends of the geological drill pipe after threading is not lower than that of the pipe body, both ends of the drill pipe must be thickened before threading. There are three types of thickening methods: inner thickening, outer thickening, and inner and outer thickening.
After cold drawing and annealing (780~830°C, 30min) of cold-drawn
seamless steel pipe, longitudinal cracks were found on the outer surface during straightening, and a large number of cracks were found in the flattening test. By metallographic examination, it was found that the structure is very uneven, and there are equiaxed ferrite crystals distributed between striped pearlite. Although it has been annealed, it is more like a hot-rolled state, or between a hot-rolled state and annealed state. organization. At the same time, large sheets of pearlite and large sheets of ferrite are alternately distributed. At the same time, inclusions were found in the steel pipe, with a grade of about 2.5. Finally, the heating temperature of the inclined bottom furnace before piercing is 1180~1230°C for 35 minutes, whether it is suitable or not, and what is the effect on the structure. Experts, please help to analyze: first, is the unevenness of the structure caused by the billet; second, is the final annealing temperature of the finished product, 780~830, suitable for the problem; third, is the possible cause of the crack is What?
Answer the following:
The unevenness of the first organization is the cause of the tube blank. 16Mn is the grade of steel in the past, and it has been changed to Q345B for a long time.
The second finish annealing temperature is appropriate. The perforation heating temperature is 1180~1230°C, which is relatively low. This is the temperature of medium carbon alloy steel, and it is suitable to take 1230-1250°C. Is 35min the heating time or the furnace time? The time in the furnace is generally more than 60 minutes.
Third, regarding the possible reasons for the cracks, I have done many experiments. The result is that the tube blank (round steel) is mostly caused by many cracks, inclusions, air pockets, etc. inside. The perforation temperature and process adjustment cannot be ignored. If the perforation temperature is low and improperly adjusted, it will also cause tearing of the internal tissue of the capillary.
