How to apply the outer casing packer in oil well cementing?

With the continuous development of oil fields, the crude oil in the formation is constantly being extracted, causing the formation pressure to decrease. In order to maintain a certain production capacity, a certain amount of water is injected into the formation to artificially increase its production capacity. After year-round water injection, especially high-pressure water injection in recent years (some areas have water pressure close to or exceeding the formation fracture pressure), the reservoir pressure generally rises; Due to poor connectivity or heterogeneity of the oil layer, local ultra-high pressure traps are formed in the oil layer, and there is a significant difference in interlayer pressure. In addition, during the drilling process of exploration or production wells, high-pressure oil, gas, and water layers are often encountered. Due to the presence of these high-pressure oil, gas, and water layers, it brings certain difficulties to cementing construction. Because during cementing construction, the cement slurry solidifies and the pressure of the liquid column decreases, causing oil, gas, and water to flow upwards. After cementing, oil, gas, and water may leak out of the casing; Poor solidification of cement slurry in the water injection layer; Vertical channeling of cement slurry, unqualified sealing of production layer or interlayer; Leakage during cementing, insufficient cement slurry return height. Affects the quality of cementing. It brings interlayer interference to layered injection and production, complicates oil production processes, reduces oil well utilization, and shortens the service life of oil wells.

In terms of solving problems, in addition to optimizing the cement slurry system, it is also necessary to use external packers to seal off oil, gas, and water layers.

1、 Application in high-pressure wells

The external packer has a good effect in solving the cementing construction of oil and gas wells with a drilling fluid density greater than 1.40g/cm3. In 2003, a total of 62 well cementing operations were carried out in Bohai using external pipe packers, with a success rate of 100%, a qualification rate of 100%, and a quality rate of 84.75%. Compared to last year, the quality rate has increased by 7.83 percentage points. We have conducted experiments in the Gudong area, where the drilling fluid density was 1.60g/cm3. A total of 30 wells were tested, including 22 wells with external pipe packers, 8 wells without external pipe packers, and 22 wells with external pipe packers. The cementing qualification rate was 100%, with a quality rate of 86.67%. Among the 8 wells without external pipe packers, the quality rate was only 50%, and the difference in quality rate between the two was 36.67 percentage points.

2、 Application in complex blocks

In the case of complex geological conditions, active underground fluids, and poor cementing quality, through statistics, comparison, analysis, and research, measures such as improving the cement slurry system and using external casing packers have greatly improved the cementing quality rate in the region.

In addition, the use of external packers in cementing construction of high-pressure oil and gas wells has also solved the problem of channeling during cement solidification in high-pressure oil and gas.

The use of external casing packer in segmented cementing is also quite widespread. After the external casing packer expands, the cement slurry returns to the outside of the casing for cementing through a multi-stage cementing device.

Application of Three in Lost Circulation Wells

Lost wells can be divided into three categories: fractured, karst lost wells, and permeable lost wells. Different construction measures should be taken for different leaks during drilling and cementing operations. According to the situation of leakage, the treatment of the leakage layer before cement injection should be carried out, and the balanced pressure cementing design should be carried out after treatment. For sections prone to leakage and collapse, conventional cement injection leak prevention measures include increasing the pre liquid with lower density, controlling the length of the cement sealing section, and using a low-density cement slurry system. It is also possible to use casing external packers to seal the above layers in layers, solving the problems of oil, gas, water migration and pressure leakage in the above well sections, resulting in insufficient return height.

In some special formations, due to the sensitivity of oil and gas reservoirs to cement slurry, the traditional cementing method of using cement slurry to seal the casing can no longer meet production requirements. We can use the external packer method to complete the well, which can ensure the normal development of oil and gas wells and effectively solve the problem of cement slurry pollution in the formation.

Conclusion 4

External casing packers not only significantly improve the quality of cementing in high-pressure oil and gas wells, but are also important in other special process wells. With the development of cementing technology, casing external packers will be widely used in cementing construction.