Mud cleaner

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Mud Cleaner

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

Desander

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.

Mud mixture of water and any combination of soil, silt, and clay

Mud is a liquid or semi-liquid mixture of water and any combination of different kinds of soil. It usually forms after rainfall or near water sources. Ancient mud deposits harden over geological time to form sedimentary rock such as shale or mudstone. When geological deposits of mud are formed in estuaries, the resultant layers are termed bay muds.

Contents

History

Although US Patent No.3,766,997 covering Mud Cleaner was issued on October 23, 1973 granted to J.K. Heilhecker and L.H. Robinson and assigned to Exxon Production Research Company, it was found invalid and efforts for re-issue was unsuccessful because of the existence of prior art filed at the British Patent Office by a German Inventor in the late 1800s.

Prior art, in most systems of patent law, is constituted by all information that has been made available to the public in any form before a given date that might be relevant to a patent's claims of originality. If an invention has been described in the prior art or would have been obvious over what has been described in the prior art, a patent on that invention is not valid.

Nowadays, mud cleaner used in oilfield means the equipment processing drilling mud. It is combined with desander cone and desilter cone as well as bottom shaker. It is called 2nd and 3rd phase solids control equipment.

Drilling fluid

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.

Description

A mud cleaner is a combination of desanders and/or desilters mounted over a shaker with a fine mesh screen. A mud is fed to the inlet of the hydrocyclone (desander and/or desilter) to separate particles and the underflow passes to the fine screen mesh where in particles larger than barite are discarded and thrown away. In most drilling operations, a mud cleaner is installed in its mud systems. It is usually located in a mud tank in the same location as with the desilters.

Hydrocyclone

A hydrocyclone is a device to classify, separate or sort particles in a liquid suspension based on the ratio of their centripetal force to fluid resistance. This ratio is high for dense and coarse particles, and low for light and fine particles. Hydrocyclones also find application in the separation of liquids of different densities.

Mud systems

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.

Process flow

The weighted mud flows to the inlet head section of the desander and/or desilter entering the hydrocyclones for separation of particles. Mud leaving the underflow is further screened with fine mesh to separate larger particles allowing only barite size particles to pass through the screen returning and recovering then the clean mud.

Purpose

The purpose of the mud cleaner is to remove drilled solids larger than barite. Solids larger than 74–105 micrometres can be removed by the mud cleaner before the viscosity builds up. Mud cleaner can effectively control weighted drilling fluid solid content. Prevent differential pressure sticking, adhesion stuck drill accident, reduce the drill string and the filter cake thickness on bond issues.

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Shale shakers

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Sieve analysis

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Sand separator

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Mud tank

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.

Solids control is a technique used in a drilling rig to separate the solids in the drilling fluids that are crushed by the drill bits and carried out of the well surface. Normally, a solid control system contains five stages: the mud tank, shale shaker, vacuum degasser, desander, desilter, and centrifuge. The shale shaker is used to separate big solids with diameter above 75μm, the desander addresses solids from 45-74μm, and the desilter segregates solids between 15-44μm. Sometimes the desander and desilter are combined as one high efficiency mud cleaner. When air enters the drilling fluids, a vacuum degasser is used to separate the air. When there is no air in the mud, the degasser works as a big agitator. All these stages are mounted on the top of the mud tank. After separating the solids, the clean mud can be pumped into the borehole again.

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