Various impurities can be reduced into the production layer: after acidifying the conventional oil
casing pipe, the wax, rust residue and adherent instruments in the pipe will be brought to the formation. If we acidify the
thickened tubing to the outside, magazines such as scaling, waxing, and rust residue in the tubing can be removed to reduce the pollution of the tubing to the formation during construction.
To avoid secondary pollution to the oil layer when performing well killing operations: One of the effective methods to improve oil production fluids is to quickly clean the formation. The reason is that after the formation is treated with acid solution, precipitation and liquid leakage will occur. The outer thickened tubing can be used to easily replace the formation with nitrogen, and the outer thickened tubing can be lifted out of the wellhead without well killing. Because the outer thickened oil pipe is a relatively closed loop system, the staff can effectively control the oil well survey, and the entire operation can be completed in the operating room. It can also effectively prevent harmful substances from being squeezed out during the process of acid removal, causing harm to the human body.
In the working process, less acid fluid is used, and the well section that is effective is longer. If we use a more common tubing string for acidification treatment, it is difficult to perform an effective acidification treatment for a longer pipe in the well section, and the amount of acid liquid is increased. If we use an external thickened tubing, it is most effective for long sections, especially horizontal wells. It can not only avoid contamination of the bottom layer, but also reduce the amount of acid liquid used.
Because of the special characteristics of the outer thick tubing, its application in horizontal wells has been widely used. In the horizontal well, the length of the downhole for the outer thickened tubing is limited. Generally, the depth of the downhole in the horizontal well is between 600 mm and 900 mm. For this situation, we can use the tubing with a small-sized pipe string.
