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How to Best Maintain Drilling Fluid Centrifuge During Use

Decanter Centrifuge(VFD) DCLW360-1200N

In drilling operation, drilling fluid centrifuge is one of the core equipment that is often used, it is mainly used for separating fine solid particles whose diameters are 2-7 μm from the drilling fluid, the use of drilling fluid centrifuge can effectively protect the drill bit, and also has a very important role in improving drilling speed. With the oil drilling industry technology is getting mature, drilling fluid centrifuge manufacturing technology has been greatly improved. However, some inherent mechanical problems are still not solved and continue to haunt users.

So, what are these problems?
Mainly for the below:
1. Bowl fault.
2. Wearing parts (inlet pipe, shockproof strip) problem.
3. Excessive vibration.
4. Outlet blocking.
5. Explosion-proof plug damage.
6. Centrifuge scroll wear.
7. Bearings failure in the process of using.
8. Drilling fluid centrifuge hose damage.

So how should we maintain the drilling fluid centrifuge during using?

The first point: the use of staff must be regular maintenance on the centrifuge, regular cleaning the inlet and outlet, add grease to the bearing parts;

The second point: regular inspect easy damaged parts on the drilling fluid centrifuge, like hoses. In order to ensure the process in the use of these parts is not a problem which influences the production. Finally, electronic products and TV sets, reduce the on-off times, when drilling fluid centrifuge started, preferably every 8 hours rather than an hour on drilling fluid centrifuge to start. Do all of the above, then you’ll find out centrifuge failure rate will be greatly reduced in use.


Before hydrocyclones and centrifuges became available for drilling applications, shale shakers and dilution were the only means of controlling the solids content of drilling fluids. Consequently, solids too fine to be separated by the shaker screens in use could be controlled only by dilution. During drilling with weighted muds, once the solids content reached the maximum acceptable level, the continuing and unavoidable incorporation of drilled solids made it necessary to add a continuous stream of water to control viscosity, while adding barite to control the mud weight. This was, obviously, a costly procedure that generated large quantities of excess drilling fluid.

The centrifuge, in splitting the processed fluid into two streams—the underflow, or ‘‘cake,’’ containing the coarser solids; and the overflow, centrate, or effluent, containing most of the liquid and the finer particles—provides a means of selectively removing the finest, most damaging, solids from the drilling fluid. The removal of these solids in order to control rheology and filter cake quality is the primary reason for centrifuging weighted drilling fluids. When the finest solids are not removed, the only alternative means of reducing their concentration is dilution, always an expensive process.

Centrifuging weighted drilling fluids routes the coarser solids (both barite and low gravity) to the underflow, and the finer solids (bentonite, barite, and low gravity) to the overflow. Separation of the overflow, consisting of the finer solids together with most of the processed liquid and the dilution fluid, reduces the concentration of the viscosity-building solids, alleviates solids problems, and reduces the need for dilution.

This application is often described as barite recovery, a term that does not accurately describe the process, leads to confusion, and is frequently the reason for improper centrifuge use. The validity of the term depends in the preliminary acceptance of the idea that the fluid entering the centrifuge would otherwise be discarded and that the barite is recovered by the centrifuge. Few, if any, drilling people think of centrifugingin these terms. Centrifuges, like shale shakers and hydrocyclones, are solids-removal devices. Centrifuging weighted muds while drilling is correctly thought of as an alternative to dilution for the reduction of viscosity; not as a means of recovering barite from discarded fluid. Another objection to the phrase is that it lends support to the idea that barite recovery is the reason for centrifuging. It is not. The objective of centrifuging in this manner is the removal of colloids and ultra-fine solids to improve drilling-fluid quality. A third objection is that the use of the term tends to create the totally erroneous impression that the process separates barite from low-gravity solids and that the recovered material is all barite. A natural consequence of this belief is that the underflow from barite-recovery centrifuges is sometimes stored and used to weight up freshly prepared drilling fluids. Inasmuch as the recovered slurry often contains high concentrations of drilled solids, it can be severely contaminated, and is rarely suitable for reuse.



The principal use of mud cleaners has always been the removal of drilled solids larger than barite. Sufficient drilling fluid bypasses shale shakers so that even with 74-micron (API 200) screens on the shakers, many drilled solids are removed from a weighted drilling fluid. When linear motion shakers permitted API 200 screens to process all of the rig flow, mud cleaner usage declined rapidly. However, whenever a mud cleaner was used downstream, the screens were loaded with solids.

A secondary use of mud cleaners is the removal of drilled solids from unweighted drilling fluids with a very expensive liquid phase—such as the initial application with the potassium chloride drilling fluid. In this case, the underflow from desilters is screened to remove solids larger than the screen opening. Solids and liquids pass through the screen and remain in the system. This is beneficial for non-aqueous drilling fluids as well as saline water–base drilling fluids.

In unweighted drilling fluids, the desilter underflow could be directed to a holding tank. A centrifuge could separate the larger solids for discard and return the smaller solids and most of the liquid phase to the drilling-fluid system. This method is easy to apply if a centrifuge is already available on a drilling rig. More drilled solids would be rejected by the centrifuge than by the mud cleaner screen; however, renting a centrifuge for this purpose may be more expensive. Both techniques have been used extensively in the field.

Centrifuge applications for weighted mud

Centrifuge can be applied in the following modes.

1 Recovering barite and removing ultra-fine and colloidal size solids in weighted mud with a single Barite Recovery Centrifuge.

The liquid phase containing fine particles is discarded as overflow to reserve pit and the solids that contain a great percentage of barite are conveyed as underflow to the circulating mud system. The purpose of this mode is to remove small colloidal particles from the mud in order to control mud viscosity. There is a large portion of mud discharged and wasted from overflow port in this operating mode.

2 Dual centrifuging for recovering barite and removing ultra- fine and colloidal size solids in weighted mud (Barite Recovery Centrifuge-High Speed Centrifuge Combination).

The first Barite Recovery Centrifuge followed by a High Speed one are applied and work jointly. The solids predominantly barite from the underflow of the first Barite Recovery Centrifuge are recovered and introduced to the mud circulating system and the liquid phase retaining fine solid particles comes out from overflow port and is discharged to a small holding tank and then is pumped to feed the second centrifuge–High Speed Centrifuge.

The solids separated by the second High Speed unit that come out from underflow port are discarded to the reserve pit and the cleaned liquid that comes out from overflow port is returned to the circulating system. The cleaned liquid separated by the High Speed Centrifuge can also be used to dilute the feed mud of the first unit–the Barite Recovery Centrifuge or dilute the recovered barite.

This dual centrifuging design is very cost effective when it is used on mud that contains precious liquids and chemicals.



Types of centrifuges

There are two types of centrifuges in this article: Decanting centrifuge and Rotary Mud Separator Centrifuge (RMS).

1 Decanting centrifuge:

The decanting centrifuge is composed of a rotating bowl and a screw conveyor inside the bowl. The rotating bowl is a cylinder but with one end in the shape of a tapered section cone that favorites coarse solids separated to move to the discharge port. The bowl rotates creating high centrifugal force that throws coarse solid particles on its inner wall and the screw conveyor rotates at a slightly slower speed pushing these coarse solid particles to the under-flow discharge port. Meanwhile the liquid cleaned out of coarse solid particles and retaining the finer particles flows to the overflow discharge port.

2 Rotary Mud Separator Centrifuge (RMS):

The RMS centrifuge is composed of a stationary case and a perforated cylinder that revolves concentrically within the case at a defined speed. Mud and water is pumped proportionally by two metering pumps into the annulus between the separator case and the cylinder. The condensed coarse solids are moved along the wall of the case and pushed out through the underflow port. The lighter liquid phase moves toward the center of the perforated cylinder and exits through the perforated rotating tube as overflow.


Adjust centrifuge for getting better separation

Drilling fluid centrifuge is the special equipment of solid-liquid separation. It can accomplish each procedure of feed, centrifugal sedimentation, unloading, etc. it mainly uses for recycling barite, eliminating small solid, reducing the solid content of drilling fluid, controlling the density and viscosity of drilling fluid, ensuring the performance of drilling fluid, and plays an important role in quick drilling. 

We can through the adjustment of centrifuge to get the best separation effect.

The adjustment of centrifuge can through the weir plate. Weir plate is the component of adjust liquid level. By replacing different weir plate, can get different radius of the liquid level.  According to whether has BD plate to determine the highest level. Has BD plate can be a higher level, if not has the BD plate can be a lower level. Generally speaking, low liquid level can get higher solid phase dryness, higher liquid level can get higher liquid phase clarity.

We can also adjust centrifuge bowl rotary speed. Higher rotary speed can get higher separation factor and better separating effect. But for some materials, the higher separation factor is not always better. After choosing suitable weir plate and rotary speed, in the operation process, we can through the adjustment of some parameters to get the best separation effect.

Of course, we need to according to the practical situation in oilfield, choose suitable adjustment of centrifuge to get better effect.


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