Analysis of Oil Well Casing Technology and Welding Process

Press Release : July 02, 2020
Analysis of Oil Well Casing Technology and Welding Process

Analysis of oil well casing technology:

Well structure damage is a common problem in oilfield mining operations. Based on the complexity of the downhole environment in the oil field, damage to tubing and casing structures is also relatively common. The latter is divided into cement ring damage caused by changes in the bottom layer. Among them, casing damage is very harmful to the oil field, which may cause production shutdown. The economic development has promoted the continuous increase of fuel oil consumption, the corresponding increase in oil mining operations, and the number of oilfield casing wells has continued to increase. Therefore, strengthening the detection of casing damage has become one of the key contents in oilfield mining operations.

In the field of oilfield casing damage detection, the application of electromagnetic flaw detection tools shows a certain degree of passiveness, and it will only be applied when the oil and gas well field is damaged. If the instrument is used in the work where casing damage has occurred, the actual inspection work will be affected by a variety of external factors during operation, and the electromagnetic flaw logging tool can basically achieve Effective application in complex environments. The author summarizes long-term practical experience and finds that the tubing in each layer of oil and water is a common damage site in oil wells, mainly composed of the tubing itself, casing pipe, and casing outer layer. This paper analyzes the casing damage situation in Jiangsu oilfield as an example, and uses electromagnetic flaw detection logging technology to detect 14 wells. It is found that these wells have casing corrosion, cracks, diameter reduction and other phenomena. Some wells are repaired under the guidance of logging results After the operation, it will get relatively good economic benefits after re-commissioning.

Welding process of petroleum casing  pipe:
(1) Selection of welding method: 80%Ar+20%CO2 gas shielded welding.
Selection of welding data: ER55-G welding wire is used, with a diameter of 3.2mm.
Welding parameters: current 250~320A, voltage 26~30V;
The welding speed is 35~50cm/min; the preheating temperature is 100℃, to ensure that the temperature between the layers is not lower than the preheating temperature, but it is not allowed to be 30℃ higher than the preheating temperature.
Post-weld treatment: air-cooled without any heat treatment.

(2) Selection of welding method: 80%Ar+20%CO2 gas shielded welding.
Selection of welding data: ER55-G welding wire is used, with a diameter of 3.2mm.
Welding parameters: current 250~320A, voltage 26~30V; welding speed 35~50cm/min; preheating temperature is 100℃, to ensure that the interlayer temperature is not lower than the preheating temperature, but also not allowed to be higher than the preheating temperature 30℃ .
Post-welding treatment: tempering treatment, temperature 600±20℃, holding time 4h; heating rate 50
℃/h, cooling rate 50℃/h.

The test blocks welded by the above two welding processes have the following experimental results:The results of the first (1) plan: tensile test, broken base material, qualified; impact value of 3 samples in heat affected zone 26, 47, 23, unqualified; four samples of side bending have 3.75mm Cracks, 4mm cracks, 1.38mm cracks, 0.89mm cracks, failed; the experiment proved that this process plan is unreasonable.

The results obtained from the plan (2): tensile test, broken base material, qualified; impact value of three samples in heat affected zone 51, 40, 40, qualified; all four samples of side bending are qualified, qualified; Experiments prove that this process plan is reasonable. Post-weld heat treatment can improve the performance of the welded structure, which is one of the important factors for whether the 37Mn5 petroleum casing can be welded to meet the technical requirements.

Notes to editors

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