The tubings used in the petroleum industry are all connected by screw thread, which connects the tubings one by one in series to the bottom of the well, and successfully realizes the functions of oil well production, gas well production and water injection through pressure test and other field work. Therefore, the screw thread and screw thread connection of the tubings are the key parts to ensure the quality and strength of the tubings, as well as the key process rework and engineering work The direct cause of this.
It has the following quality hidden dangers in downhole operation and production of oil, gas and water wells:
1. Due to the lack of tubing thread, the thread is not sealed, resulting in unqualified hydrostatic pressure test of the string of oil extraction pump in the mechanical production well, resulting in the failure of the next pump process.
2. There is a defect in the thread of the tubing, so the safety factor must be reduced, resulting in the decrease of the tensile strength of the thread. Under the action of heavy load, the thread is easy to slip, which leads to the accident of falling objects.
3. Under the action of high injection pressure, when the injection pressure in the tubing exceeds 10MPa of the casing pressure, the pressure difference between the tubing and the casing is too large, the pressure difference of the casing is unbalanced, and thread leakage is easy to occur, resulting in the failure of the packer stratified water injection well string.
4. The production pressure difference between the tubing and the casing is too large, which is prone to thread leakage, so that the production pressure in the tubing and the casing is out of balance control, resulting in water accumulation at the bottom of the well, which leads to the failure of the gas production string.
All of the above hidden dangers occur in the aspect of tubing thread defects, which seriously affect the oil recovery rate and the improvement of oil recovery, resulting in the increase of production cost.