The solid control equipment used in drilling operations is key equipment used to separate and remove solid particles from the drilling fluid during the drilling process. The solid control equipment system can ensure the cleanliness of the drilling fluid, reduce the solid phase content in the drilling fluid, thereby improving drilling efficiency, protecting the drill bit, extending equipment life, and reducing environmental impact. It is an indispensable part of modern drilling technology.
Among the entire set of solid phase removal equipment, the shale shaker is characterized by the fastest and earliest separation of drilling fluid solids. It is an economical and highly efficient separation device. The drilling fluid returned from the well first passes through the shale shaker and then enters other solid control equipment. Therefore, the proper use of the shale shaker is the prerequisite for fully utilizing the roles of other solid control equipment. Given its importance, how can we determine the quality of a shale shaker?
The factors that determine the quality of a shale shaker include: vibration type, amplitude and frequency, the inclination of the shaker screen, and the size and weaving method of the shaker screen.
There are three types of movement forms of the shale shaker: circular, elliptical, and linear motion. Each movement type is generated by the different positions of the vibrator in relation to the system's center of gravity. When the vibrator is at the system's center of gravity, it generates circular motion; when the vibrator is above the system's center of gravity, it generates elliptical motion. For elliptical motion, the screen surface must have an inclination to facilitate the transport of drilling cuttings. However, the inclined screen surface reduces its screening capacity. Linear motion is achieved by placing the vibrator in front of the upper system's center of gravity, causing the screen frame to produce linear motion, thereby removing solids. Linear motion has a fixed cuttings transport speed, and the screen surface can be flat or slightly inclined.
The screening capacity of the shale shaker depends on three parameters: amplitude or stroke, vibration type, and the vibrator's rotational speed. The rotational speed of the vibrator determines the frequency of the shale shaker. The higher the rotational speed, the higher the vibration frequency, resulting in more effective solid phase removal.
The amplitude of the shale shaker is determined by the weight and eccentric distance of the vibrator. The so-called amplitude refers to the vertical motion distance of the shaker screen. Vibration intensity indicates the centrifugal acceleration produced by the vibrator relative to the gravitational acceleration. It reflects the force exerted by the screen on the solid particles.
Theoretically, the larger the amplitude of the shale shaker, the better the sand removal effect. However, with increased vibration intensity, the forces acting on the shaker also increase, shortening its lifespan. Therefore, design and use should comprehensively consider these factors. Most circular motion shale shakers have an acceleration of 4-6 times g, while most linear motion shale shakers have an acceleration of 3-4 times g.
The shale shaker screen drives the entire drilling fluid movement through vibration to separate solids. Elliptical motion shale shakers are usually placed at different inclinations. The purpose is to rationally discharge cuttings, with the screen surface being one inclined plane or divided into several inclined planes. The inclination angle of the screen surface significantly impacts particle movement speed and screening efficiency. An appropriate inclination angle can improve screening efficiency and processing capacity. Multi-layer shale shakers have multiple screens, where drilling fluid must pass through the first screen before entering the second, and so on.
There are two ways to represent screen size: mesh diameter and mesh count. If the size of the shale shaker screen is inappropriate or torn, the efficiency of solid phase separation will drop dramatically. If the screen is improperly installed and lacks support, it will quickly wear out or tear. Therefore, it is vital to select an appropriate screen size and ensure proper installation.
The weaving method is an essential factor in screen design. Primary weaving methods include plain square weave, rectangular weave, plain weave, and twill weave. Among them, square and rectangular weaving methods are the most commonly used. For the same mesh size, square mesh generally removes more solid phases than rectangular mesh. This is because square mesh is less prone to blinding, can be woven with thicker wire to extend screen life, and has larger mesh areas and screening capacities to improve the shale shaker's ability to process drilling fluids.
In addition, the processing capacity and stability of the shale shaker, its suitability and versatility, and power consumption are also factors to consider. By comprehensively considering these factors, one can select a high-performance shale shaker that meets practical needs, ensuring optimal performance in drilling operations.
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