Hydroxyethyl Cellulose * Well Completion and Workover

Ⅰ. The role of hydroxyethyl cellulose (HEC) in completion operations

1. Improved filtration performance

During the completion process, filtration control is crucial. HEC can effectively reduce the filtration loss of completion fluid. When the completion fluid contacts the formation, the liquid will penetrate into the formation under the action of pressure difference. If the filtration loss is too large, it will cause changes in the performance of the completion fluid, such as reduced viscosity, and may also cause damage to the formation. HEC forms a gel-like structure in the completion fluid, which can form a filter cake on the surface of the well wall, reducing the filtration loss of liquid into the formation, just like building a "barrier" around the well wall to prevent excessive penetration of liquid.

2. Improve sand carrying capacity

For some situations where gravel packing and other operations are required during the completion process, HEC can enhance the sand carrying capacity of the completion fluid. The completion fluid needs to smoothly transport supporting materials such as gravel to the destination. HEC increases the viscosity of the completion fluid, allowing gravel to be evenly suspended in the completion fluid, ensuring the correct placement of gravel in the wellbore, and helping to improve the stability and conductivity of the wellbore.

3. Stabilize the well wall

HEC helps stabilize the well wall. During the completion stage, the well wall may become unstable due to various factors (such as changes in formation pressure, fluid flushing, etc.). HEC can form a protective film on the well wall to enhance the stability of the well wall. This protective film can prevent the peeling and collapse of the well wall, ensure that the completion operation can proceed smoothly, and also help to extend the service life of the oil well.

4. Adjust rheology

It can adjust the rheology of the completion fluid so that the completion fluid can maintain good performance under different operating conditions (such as different temperatures, pressures and shear rates). By adjusting the amount of HEC added, completion fluids with different rheological properties can be obtained to adapt to complex completion environments, such as high-temperature and high-pressure wells or horizontal wells.

Ⅱ. The role of HEC in well repair operations

1. Carrying impurities and suspended particles

During well repair operations, a large amount of impurities such as rust, rock cuttings, scale flakes, etc. will be generated underground. HEC can increase the viscosity of the repair fluid, thereby effectively carrying these impurities to the ground. At the same time, for some situations where chemical agents or materials need to be added for downhole treatment, HEC can ensure that these agents or materials can be evenly suspended in the well repair fluid and play their due role.

2. Lubrication

During the well repair process, the friction between the tool and the well wall and between the pipe and the well wall is an important factor to consider. HEC can improve the lubrication properties of the well repair fluid and reduce friction resistance. This can prevent tools and pipes from getting stuck, reduce the difficulty and risk of well repair operations, and improve operational efficiency.

3. Anti-corrosion protection

Metal equipment in the well (such as oil pipes, casing, etc.) is susceptible to corrosion. HEC can form a protective film on the surface of metal equipment to reduce the damage of corrosive media (such as formation water, acidic gas, etc.) to the equipment. This helps to extend the service life of downhole equipment and reduce well repair costs.