Before getting into the details of how shale shakers screen drilling the mud and what will happen during the process, it is vital to know what a shale shaker is? Shale Shaker is an industrial equipment used to remove large solids from the drilling fluids. This fluid is also known as drilling mud due to its muddy appearance. Drilling mud cools and lubricates the equipment a little bit; therefore, it has become an integral part of the drilling process. Industrial fluids are expensive to produce; that’s why shale shaker is brought into use as it improves the rig’s economy by taking away the disposal’s cuttings before the fluid enters the recycling phase.
Shale shakers comprise screens or vibrating sieves which utilize force to advance the filtration process of the mud through to the mud tank. At the time of this operation, the inclination of the screen may vary according to proportional to the mud flow rate.
A Shale shaker is an important element of the drilling process and represents the first phase of solids control in drilling industries such as mining, coal cleaning, and gas and oil production. They are considered an important piece of equipment in the solid control system as the performance and efficiency of all subsequent elements depend on the cleanliness of the drilling fluid.
A Shale shaker is intensive vibrating equipment. At the initial mud separation stage, they use a motor to develop vibrations. Here shale shaker acts as a sieve, and its vibration pushes the drilled mud through a wire cloth screen. If required, the drilled mud is filtered through the shaker screen and moved into the mud tank for additional processing. A large piece of solids then passes over the screen surface and is discharged for collection and disposal.
This shale shaker represents the use of the recent shaker technology. This equipment follows the most common approach to solids control in oil and gas drilling industries. This shale shaker produces linear motion via a pair of eccentric shafts rotating in the reverse direction. Due to linear motion, it provides superior cutting conveyance; this equipment can operate on the uphill slope to improve liquid retention.
If you want to drill the top-hole section, then this shale shaker is effective for you. It can effortlessly handle high volume and heavy solids in the system. There is a difference in the power of a balanced elliptical motion shale shaker between two vibrating motors, resulting in an unbalanced force. With this setup, elliptical motion shaker, you can effectively remove the solids and eliminate the large particles present in the drilling fluid. It has relatively moderate vibration strength of the balanced elliptical shale shaker to reduce consumption of screen.
It has a single vibrator shaft located at the centre of the mass of the shaker tray. It is a motor drive concentric shaft fitted with its essential counterparts, providing pure circular motion with the length of the vibrating tray. This feature enhances the solid’s movements off the deck in comparison with an unbalanced elliptical tray. The circular motion of the device transports solids along with the screen, reducing the loss of drilling fluid. This type of shale shaker is operated as a stacked unit with the coarse screen present on the top deck fine.
A Shale shaker screen is a woven cloth made of stainless steel and used for the mud screening on the shakers. This wired cloth is specified with the term mesh. The mesh has a wide number of openings per linear inch. The mesh designation is not enough to describe the screen; the wire size influences the percentage of open area and the opening size of the screen. The more the diameter of the wire is finer, the greater will be the capacity of the screen. It would be highly undesirable too if the screen opening will be great and its life will be less. There is a huge compromise between the shale shaker’s capacity, opening size, and life.
Screen designations have become complicated because screens are rectangular in shape rather than square in openings. This type of screen can have 80 openings per inch in one direction while 40 in the other. This type of screen can be specified as an 80X40 mesh screen. It is a great capacity in comparison to the square mesh, but it allows some particles to pass through that were retained by the square 80 mesh.
Confusion in this context leads to an insufficient screen description. However, you might see the indiscriminate use of the word equivalent screens and represent the screen as one size screen, which is, in reality, something else. To describe the screen properly, the opening size and mesh in both directions and the percent of open are required.
The screen opening and particle sizes are measured in microns. A micron is 1/1000 of a millimetre. According to the size range of various particles, the size range can be removed by different solid control and screen equipment.
Drilled solids might be present in the fluid in different ranges varied from the finest dispersed bentonite 0.05 microns up to the largest cuttings. The ultimate purpose of the shale shaker screening is to remove as much as drilled solids as possible that are larger than the barite particles. In the same way, barite, bentonite, and the liquid phase of drilling mud contain a large number of chemicals that are salvaged. On the other hand, drilled solids like coarse are discarded. Since a very small amount of the mud that contains these larger particles are lost from the process, shale shaker screening turns out to be an economical way to remove these drilled solids.
With the repetition of the process, the drilled solids become smaller in size and continue to circulate in the mud system. When they become the size of barite, it becomes nearly impossible to separate them from the barite until they become smaller than the baste particles. At the same time, a centrifuge can be used to separate a portion of the liquid fraction of the mud containing small particles along with bentonite and chemical. The solid control process is quite expensive and only removes small fractions of the drilled solids. It is imperative to remove as much of drilled solids as possible before they reach the surface.
For several years, shale shakers didn’t exist that could handle the right volume of the requirement of the fine screens. Earlier conventional shakers were equipped with 12 to 20 mesh screens. This permit all types of particles less than 840 microns to incorporate into the mud and cause necessary dilution to manage mud properties.
The recent improvement in the shale shaker allows the effective use of a much finer screen than wasn’t possible with conventional shakers. These new age shakers are larger in size and can operate at a higher frequency in comparison to the conventional shakers. Some of them are even designed flawlessly so that amplitude and speed can be changed to the requirement of different types of diluted muds. Under the normal operating condition, the new age shale shaker will be able to handle 400gal/min of the mud with 80 mesh and 178-micron screen. Albeit, the specification of the shale shaker varies somewhere depending on the manufacturer involved in it.
Increased viscosity of the mud can reduce the shale screen capacity. According to the rule, the capacity of the device will be reduced by 2 percent with an effective increase of 10 percent viscosity. Also, it is important to start the process with a coarse screen and later change them to a finer screen with a decrease in the flow rate or reduction in the drilled solid content. Where the rate of the flow is low, it has sometimes been possible to screen high-weight muds with even two shale shakers using a screen that is fine as 200 mesh.
Maximum attention should be given to maintaining the shale shaker in pristine condition and making sure that the finest screens are used to handle the entire mud stream all the time. Always remember the fact that every pound that has been missed by the shaker will cost the business several times as much effort is required to remove and treat the other mud system from any other means.
An important aspect to be remembered for the entire process
If you have any estimate of the pound of the drilled solids removed by the shale shaker, then divide this number by the rental of the equipment and the cost of the screen replacement, the result of this calculation will give you the cost per pound of the solids removed. The comparison of these two numbers will derive the advantage business has got by using shale shaker. In most cases, the cost of a shale shaker turns out to be less than the dilution cost from total to spud depth.
Lifting the cutting out of the hole or diluted mud that retard dispersion in the minimum amount of time aid the screening efficiency. This makes sure that possibly large particles have been removed, allowing the maximum amount to be removed by the process of screening. Oil mud is good at inhibiting the dispersion of shale particles. In general, fine screen shale shakers can control the buildup process of drilled solid contents present in oil mud only with the minimum amount of necessary dilution.
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