Effective Ways to Stop Cement Slurry Leaks in Screen Casings for Oil Wells

In recent years, with the continuous development of horizontal well technology and the expansion of its application scale, it has become one of the important means for efficient development of oil fields. The advantage of horizontal wells is that they can reduce the resistance to the flow of crude oil from the formation to the wellbore, thereby improving oil recovery efficiency. Usually, open-hole screen casing is used for sand control in the oil layer, and cement injection on the top of the screen above the deflection section is used to complete the well. These processes are designed to ensure the stability of the wellbore and the effective collection of crude oil.

However, during the cement injection process, some unexpected situations may occur. For example, due to tool problems or special conditions downhole (such as the failure of the seal of the outer pipe packer), cement slurry leaks into the screen casing section, thereby sealing the oil layer. This situation requires timely technical measures to reopen the oil layer and establish a crude oil production channel to ensure the normal development and production of the oil field.To deal with this situation, the following technical measures can be taken:

First, consider the use of acidizing treatment technology. By injecting acid, the solidified cement slurry can be dissolved, re-opening the reservoir channel, so that the crude oil can flow smoothly to the wellbore. This method requires selecting the right acid concentration and injection method to ensure that the acid can effectively dissolve the cement without damaging the wellbore structure.

Secondly, mechanical clearing technology can be used. Special mechanical tools, such as rotary drills or sweepers, are used to mechanically clear the cement-sealed area to restore the production capacity of the oil reservoir. This method requires precise control of the strength and direction of mechanical tools to avoid secondary damage to the wellbore and oil formation.

In addition, fracturing technology may also be considered. By injecting fracturing fluid, solid blockages in the oil layer are broken up and crude oil production channels are re-established. Fracturing technology requires parameter adjustments based on formation conditions and wellbore conditions to ensure pressure and liquid flow control and avoid unnecessary impact on the wellbore.

In addition to the above technical means, methods such as hydraulic impact and chemical dissolution can also be combined, and an appropriate technology combination can be selected according to the actual situation to restore the productivity and benefits of horizontal wells to the greatest extent.

Through the comprehensive application of measures such as strictly controlling the cement injection process, real-time monitoring technology, strengthening training and guidance, setting up safety equipment, and strengthening communication and collaboration, the screen tubes can be effectively prevented from leaking into the cement slurry and the normal development and production of the oil field can be guaranteed.

With the gradual maturity of horizontal well technology and the expansion of its application scale, it has become an important means to adjust and tap potential in old oilfield areas to increase oil recovery, and to build and efficiently develop new areas' production capacity. However, during the completion process of cement injection at the top of the horizontal well pipe, due to tool problems or special conditions downhole, cement slurry may leak into the screen casing section, thereby solidifying the oil layer. The technical solution currently adopted is to drill the plug string in the next trip, use a drill bit to drill out the cement plug in the screen pipe, then use a perforating gun to perforate the cement sheath outside the screen casing, and then lower the pipe scraper to scrape the pipe. Finally, clean the well. Although this technical solution is effective, it has some shortcomings:

During the process of drilling cement plugs, the drill bit can easily cause eccentric wear on the base pipe part of the screen tube, thus affecting the strength and stability of the screen tube.

After a small sand filter pipe is suspended in the screen tube, the inner diameter will become smaller, which will limit the size of the tools during later operations and bring inconvenience and restrictions to the construction.

The treatment cycle is long and the completion cost is significantly increased after secondary sand control in the pipe, which has a negative impact on production costs and efficiency.

Therefore, the production site urgently needs a new device for processing screen casing outer cement rings to reduce production costs and improve economic benefits. This device should be able to quickly and accurately handle the cement ring outside the screen casing without affecting the base pipe part and inner diameter of the screen casing, making subsequent operations smoother and more efficient. Through such technological innovation, the development efficiency and economic benefits of horizontal wells can be effectively improved, and the sustainable development of oil fields can be further promoted.