The causes of screen casing plugging and the measures of treatment

Date:2024-04-24Tags:Screen Casing, Casing, well casing, casing and tubing,slotted casing


Screen Casing Plugging: Causes, Identification, and Effective Treatment Methods

As oilfield development enters the middle and late stages, the wellbore environment is deteriorating day by day, and the impact of sand and wax formation on the downhole pipe strings of oil wells is increasing. In the management of mechanical production, it is often found that the oil well performance map type is insufficient liquid supply or affected by gas, and the submergence degree is greater than 500 meters. The data is abnormal and the data is unqualified. However, after analyzing the structure of the oil well string and the working principles of each part, it is more reasonable to define this type of well as a screen casing plugged well. In oil wells or other pipelines, both screen casing and slotted casing may cause blockage, but the causes and methods of blockage are different. Screen casing is a casing with filtering function. Its main function is to prevent solid particles from entering the inside of the pipe and protect underground equipment from damage. Therefore, if the formation at the bottom of the well contains a large amount of solid particles or impurities, these particles may clog the filter holes of the Screen causing the bottom well flow to be blocked, thereby affecting the efficiency of oil production or water injection.

Screen Casing


What is Screen Casing?

Screen casing is a specialized well casing designed with filtration capabilities to prevent solid particles, such as sand and debris, from entering the production tubing. By protecting downhole equipment and maintaining well integrity, screen casing plays a critical role in oil production. However, when solid particles or impurities accumulate in the filtering holes, they can obstruct fluid flow, leading to decreased production efficiency and increased maintenance requirements.


Primary Causes of Screen Casing Plugging

There are three main reasons why the screen casing is blocked:


1.Sand Production in Oil Wells

After the oil well is fractured, the fracturing sand is spit back into the wellbore or sand is produced from the formation. During the pumping process, the sand blocks the screen tube.


2.Wellbore Environmental Conditions

Due to the harsh environment of the wellbore, a false liquid level was produced when testing the fluid level, resulting in a high degree of submergence. However, in fact, the submergence degree of the oil well was low. The performance diagram was due to insufficient liquid supply or gas influence, and inaccurate test data resulted in screen tube plugging.


3.Wax Formation

The wax content in the oil well is high, and if it has not been removed for a long time, wax will accumulate on the outer wall of the screen casing and block the liquid inlet channel.


How to Identify Screen Casing Blockages?

1.The production dynamic characteristics of oil wells show low liquid volume and low flow pressure, and tests show that the formation energy is relatively sufficient.

2.The liquid production capacity increased significantly after routine pump inspection, and the liquid production capacity gradually decreased during the later production process, which is consistent with the typical characteristics of "physicality", "graduality" and "repeatability" of the screen casing clogging mechanism.


Methods to control oil well screen casing clogging.

Strengthen cleaning: Since the nature of blockage is physical blockage caused by sand accumulation of clay particles, we can learn from the well cleaning and killing process during conventional operations, and squeeze and inject large quantities of production water from the casing and tubing annulus to the near-well area. The pressure fluctuation generated during the squeezing process and the flow of the injected fluid into the formation are used to "disperse" the clay and gravel blocking layer outside the screen casing, and migrate and disperse away from the screen casing to relieve tube blockage.

Strengthen chemical cleaning management: For false liquid levels caused by dirty oil wells and screen casing plugging caused by slight wax deposits in the wellbore, after multiple tests have confirmed that the performance diagram and liquid level data are correct, cleaning should be carried out immediately to prevent the oil pump from Insufficient liquid supply for a long time will cause dry grinding and burning of the pump and restore oil well production in a timely manner.

Use a positive circulation hot-wash oil pump: For oil wells with severe sand production and wax formation, resulting in screen casing plugging that cannot be successfully treated by cleaning, it is necessary to use pipe string operations.


In conclusion:

Taken together, if the possibility of clogging is considered, a suitable pipeline design needs to be selected based on specific formation conditions, bottomhole fluid properties and operating requirements. Generally speaking, screen casing is more susceptible to clogging in formations that tend to contain large amounts of solid particles; while in formations with high sand content, slotted casing may also face clogging problems. Therefore, during the design and use process, it is necessary to comprehensively consider a variety of factors and take corresponding anti-blocking measures to ensure smooth flow at the bottom of the well.

We use cookies to offer a better browsing experience, analyze site traffic, and personalize content. By using this site, you agree to our use of cookies.

Accept
Decline