Shale shakers

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Typical shale shakers on a drilling rig Shale Shakers.jpg
Typical shale shakers on a drilling rig

Shale shakers are components of drilling equipment used in many industries, such as coal cleaning, mining, oil and gas drilling.They are the first phase of a solids control system on a drilling rig, and are used to remove large solids (cuttings) from the drilling fluid ("mud").

Contents

Drilling fluids are integral to the drilling process and, among other functions, serve to lubricate and cool the drill bit as well as convey the drilled cuttings away from the bore hole. These fluids are a mixture of various chemicals in a water or oil based solution and can be very expensive to make. For both environmental reasons and to reduce the cost of drilling operations, drilling fluid losses are minimized by stripping them away from the drilled cuttings before the cuttings are disposed of. This is done using a multitude of specialized machines and tanks.

Shale shakers are the primary solids separation tool on a rig. After returning to the surface of the well the used drilling fluid flows directly to the shale shakers where it begins to be processed. Once processed by the shale shakers the drilling fluid is deposited into the mud tanks where other solid control equipment begin to remove the finer solids from it. The solids removed by the shale shaker are discharged out of the discharge port into a separate holding tank where they await further treatment or disposal.

Shale shakers are considered by most of the drilling industry to be the most important device in the solid control system as the performance of the successive equipment directly relates to the cleanliness of the treated drilling fluid.

Mudloggers usually go out and check the shakers for rock samples that have circulated from bottom. They separate the rock from the drilling fluid and take it into an onsite lab where they dry out the samples and label them according to depth. They then look at the samples and analyze what kind of rock they have at a certain depth. This helps determines what depth that type of rock was encountered.

Structure

Shale shakers consist of the following parts:

Oil well shaker Oil well Shaker.JPG
Oil well shaker
Some feeders can be equipped with a bypass valve at the bottom of the feeder which allows the drilling fluid to bypass the shaker basket and go directly into the hopper and back into the mud system without being processed by the shaker screens.
New Shale Shakers New Shale Shakers.JPG
New Shale Shakers
As a rule of thumb the beach and pool are maintained at a ratio of 80% pool and 20% beach, this of course can change depending on the requirements of cutting dryness and flow rates.
There are various angling mechanisms currently in use which vary from hydraulic to pneumatic and mechanical, they can be controlled from either one side of the shaker or must be adjusted individually per side. Mechanical angling mechanisms can be very dependable often requiring less maintenance but usually take more time to operate than their hydraulic or pneumatic counterparts whereas the hydraulic/pneumatic angling mechanisms are much faster to operate and require less a physical means of operation.
Mudloggers collecting samples out of the shakers Mudloggers collecting samples out of the shakers.JPG
Mudloggers collecting samples out of the shakers
Some shakers come with an optional third motor on the shaker bed, this motor is most often used to modify the elliptical motion of the basket making it more circular therefore "soften" the motion, but comes at a cost of decreased G's and slower conveyance of the cuttings. This motion is usually used for sticky solids. NOV Brandt VSM 300 shale shaker is the world’s first balanced elliptical motion shaker. [1]

Shaker screen panels

A shaker screen consists of the following parts:

Oil rig shaker Oil Rig Shaker.JPG
Oil rig shaker
These differing panel shapes are used in an attempt to reduce the quantity of panels on each frame but still provide maximum rigidity and support for the mesh attached to them. The purpose of reducing these panels is to maximize usable screening area as the walls of each panel get in the way of the mesh and prevent it from being used, this is known as "blanking". The non-blanked screening area of a shaker screen is widely used as a selling feature, the more screen surface you have available to work the more efficient your shaker becomes and therefore can handle a higher quantity of fluid.
To maximize screen life most manufacturers build their screens with multiple layers of mesh over a very sturdy backing cloth to further protect the cloth against solids loading and wear. The multiple layers of mesh act as a de-blinding mechanism pushing near sized particles, which may get stuck in the openings, out of the mesh reducing blinding issues and keeping the screen surface available for use.
Plastic composite screens tend not to use adhesives but rather heat the mesh and melt it into the screen frame to form a bond.
There are many proven studies by Derrick solutions in regards to the reason for the improved performance of these 3D screens such as:
  • Increasing the screening area of each panel transfers the load across more surface area and therefore the wear tends to be decreased in comparison to other screens.
  • The corrugated shape of the screens encourages solids to settle in the valleys of the screen, keeping the peaks of the screen available to process drilling fluid.
  • The tapered valleys, while moving under high G's, apply a compression force on the solids similar to wringing out a cloth to draw out liquid.
  • Increasing the surface area of the shaker allows the use of finer screens earlier in the drilling process while maintaining acceptable flow rates and penetration rate. Effectively removing harmful drilled solids before they can begin to wear out the solids control equipment.

There are many theories on screening performance that yields inconsistent results. The only way to truly gauge the performance of any screen is to try it out and collect comparative data of your own.

Causes of screen failure

The causes of premature screen failure are:

API standards

API Standard Screen Identification FSIAPIlabel2.jpg
API Standard Screen Identification

The American Petroleum Institute (API) Screen Designation is the customary identification for screen panels. This includes:

Related Research Articles

In petroleum exploration and development, formation evaluation is used to determine the ability of a borehole to produce petroleum. Essentially, it is the process of "recognizing a commercial well when you drill one".

<span class="mw-page-title-main">Mesh</span> Material of connected strands of metal, fiber, or other flexible or ductile materials

A mesh is a barrier made of connected strands of metal, fiber, or other flexible or ductile materials. A mesh is similar to a web or a net in that it has many attached or woven strands.

A mud engineer works on an oil well or gas well drilling rig, and is responsible for ensuring the properties of the drilling fluid, also known as drilling mud, are within designed specifications.

<span class="mw-page-title-main">Drilling fluid</span> Aid for drilling boreholes into the ground

In geotechnical engineering, drilling fluid, also called drilling mud, is used to aid the drilling of boreholes into the earth. Often used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also used for much simpler boreholes, such as water wells. One of the functions of drilling mud is to carry cuttings out of the hole.

<span class="mw-page-title-main">Mud logging</span>

Mud logging is the creation of a detailed record of a borehole by examining the cuttings of rock brought to the surface by the circulating drilling medium. Mud logging is usually performed by a third-party mud logging company. This provides well owners and producers with information about the lithology and fluid content of the borehole while drilling. Historically it is the earliest type of well log. Under some circumstances compressed air is employed as a circulating fluid, rather than mud. Although most commonly used in petroleum exploration, mud logging is also sometimes used when drilling water wells and in other mineral exploration, where drilling fluid is the circulating medium used to lift cuttings out of the hole. In hydrocarbon exploration, hydrocarbon surface gas detectors record the level of natural gas brought up in the mud. A mobile laboratory is situated by the mud logging company near the drilling rig or on deck of an offshore drilling rig, or on a drill ship.

<span class="mw-page-title-main">Drill cuttings</span> Fragments of rock resulting from drilling

Drill cuttings are broken bits of solid material removed from a borehole drilled by rotary, percussion, or auger methods and brought to the surface in the drilling mud. Boreholes drilled in this way include oil or gas wells, water wells, and holes drilled for geotechnical investigations or mineral exploration.

The annulus of an oil well or water well is any void between any piping, tubing or casing and the piping, tubing, or casing immediately surrounding it. It is named after the corresponding geometric concept. The presence of an annulus gives the ability to circulate fluid in the well, provided that excess drill cuttings have not accumulated in the annulus, preventing fluid movement and possibly sticking the pipe in the borehole.

A vibrator is a mechanical device to generate vibrations. The vibration is often generated by an electric motor with an unbalanced mass on its driveshaft.

Mechanical screening, often just called screening, is the practice of taking granulated or crushed ore material and separating it into multiple grades by particle size.

Introduction

<span class="mw-page-title-main">Mud tank</span>

A mud tank is an open-top container, typically made of square steel tube and steel plate, to store drilling fluid on a drilling rig. They are also called mud pits, as they were once simple pits in the earth.

A flow line, used on a drilling rig, is a large diameter pipe that is connected to the bell nipple and extends to the possum belly and acts as a return line,, to the mud

<span class="mw-page-title-main">Desander</span> Equipment that separate sand and silt from the drilling fluids

Desanders and desilters are solid control equipment with a set of hydrocyclones that separate sand and silt from the drilling fluids in drilling rigs. Desanders are installed on top of the mud tank following the shale shaker and the degasser, but before the desilter. Desander removes the abrasive solids from the drilling fluids which cannot be removed by shakers. Normally the solids diameter for desander to be separated would be 45~74μm, and 15~44μm for desilter.

<span class="mw-page-title-main">Mud systems</span>

Effective solids control can be attributed to the overall performance of all the components of the mud systems. Conditioning the drilling fluid with the goal of dramatically lowering maintenance cost, avoiding excessive chemical treatment and maintaining mud systems volume will decrease the chance of equipment failure, unnecessary high mud costs, hole and drilling problems.

<span class="mw-page-title-main">Solids control</span>

Solids control is a process used in drilling rigs which use drilling fluid. It involves separating the "cuttings" from the fluid, allowing it to be recirculated or discharged to the environment.

<span class="mw-page-title-main">Mud cleaner</span>

A mud cleaner is a combination of desanders and/or desilters to remove drilled solids from mud.

Oil-based mud is a drilling fluid used in drilling engineering. It is composed of oil as the continuous phase and water as the dispersed phase in conjunction with emulsifiers, wetting agents and gellants. The oil base can be diesel, kerosene, fuel oil, selected crude oil or mineral oil.

Tumbler screening is a separation method that uses three-dimensional elliptical movement to separate very fine particles from larger ones.

Gyratory equipment, used in mechanical screening and sieving is based on a circular motion of the machine. Unlike other methods, gyratory screen operates in a gentler manner and is more suited to handle fragile things, enabling it to produce finer products. This method is applicable for both wet and dry screening.

References

  1. "High quality shale shaker". Aipu solids control.