How to install oil casing correctly

What is oil casing?

Oil casing is a steel pipe used to support the wall of oil and gas wells to ensure the normal operation of the entire oil well after drilling and completion. Several layers of casing are used for each well according to different drilling depths and geological conditions. Cement cementing should be used after the casing is run down the well. It is different from tubing and drill pipe and cannot be reused. It is a one-time consumable material. Therefore, the consumption of casing accounts for more than 70% of all oil well pipes.

Note: The petroleum casing is mostly API standard seamless pipe, the reason is that the seamless pipe has better performance than the welded steel pipe. (Seamless pipe means a pipe with a hollow section, which is used in large quantities for conveying fluids)

Installation method of oil casing

The oil casing is composed of a coupling and a pipe body. In order to ensure the function and facilitate transportation, the separate pipe body and the coupling are bolted and transported to the oil and gas field. In order to strengthen the compressive strength and tightening operation of the bolted connection, electric welding is required after the coupling and the pipe body are bolted. Therefore, it is particularly important to analyze the electric welding characteristics of thirty-seven Mn5 and formulate a scientific and reasonable welding method.

After each technical oil casing and oil layer oil casing are fixed, if the concrete does not return to the road surface, a part of the oil casing floats in the wellbore without a supporting point, which is a free oil casing. The force of this part of the oil casing presses on the sealed oil casing. During manufacturing, the pressure and temperature of the free oil casing will cause the expansion of the oil casing to change the internal stress, which is easy to damage the oil casing. Therefore, the casing head should be refitted after the concrete waits to set, so that the annulus between the sealed double-layer oil casings and the force of a part of the free section of the suspension oil casings.This force is pressed against the surface oil casing.

The casing head is divided into slip type and screw type according to the structure of the suspension oil casing, including the oil layer oil casing, the technical oil casing and the three-layer oil casing of the surface oil casing. A layer of casing head is installed on the top of the surface oil casing, and is connected with the pipe thread of the surface oil casing with threads. The level of the flange of the casing head is basically flush with the road surface. After the technical oil casing is fixed with concrete, a part of the free section is suspended, and the slip is seated in the cone of the casing head.Make the suspension press on the cone and seal the annulus between the double-layer oil casings and remove the landing section.

Mastering the correct installation of oil casing can avoid

1) During the drilling process, with the increase of the well depth, the required mud density will increase, and the upper bottom layer will be in danger of being pressurized and leaked. The function of the casing is to prevent the upper layer from being pressurized and leaked when drilling the lower layer.

2) The last oil pipe and tail pipe are the oil passages. Of course, it is for the instability of the formation and to prevent collapse. If the formation is hard, it can be done open hole.

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