Method summary for solid control in drilling fluid

There are four kinds of solid phase control methods of drilling fluid, which is the dilution of water, the replacement of the drilling fluid, pool sedimentation and mechanical equipment to remove the solid phase. The use of chemical flocculation can significantly improve the effect of pool sedimentation and removal of solid phase with mechanical equipment. However, the flocculant itself can not play the role of separating the solid phase, it must be used with mechanical sand removal equipment together can it receive the expected results

One: Water dilution

Dilution of the drilling fluid with water is one of the most basic methods of solid phase control. When the water was added into the drilling fluid system, the volume of the system increased, but the total amount of the solid phase was not changed, so the volume content of the solid phase was decreased in the system relatively. At the same time of adding water, it also need to add a considerable amount of processing agent in order to keep the original drilling fluid loss. Therefore, water dilution method not only to increase the drilling fluid storage equipment, but also consume a lot of water and processing agent, so that the cost of drilling fluid is increased. And it is also easy to make the performance of the drilling fluid fluctuate, resulting in complex underground conditions.

solid-control-system

Two: Replace part of drilling fluid

With clear water or solid content of the drilling fluid to replace a certain volume of high solid content of the drilling fluid, so as to achieve the purpose of reducing the solid phase content. Substitution method can reduce the amount of water and treatment agent, but after all, it will waste a lot of drilling fluid and consume a lot of treatment, it is not a good way to remove the solid too.

Three: Big pool precipitation

This method is widely used in the field. Solid phase and liquid phase have the density difference, after a certain period of time, the debris will be separated from the mud under the gravity action. Settling efficiency increase with the reduce of drilling fluid density, viscosity and the increase of the particle size. But when the viscosity of drilling fluid is larger (larger than 20 seconds), especially with shear, the falling velocity of particle was significantly slower.

Four: Mechanical equipment to remove solid phase

Commonly used machinery equipment are three types of shale shaker, cyclone treatment machine and centrifuge, distinguished by the size of the particle separation, hydrocyclone can be divided into three kinds of desander, desilter and super cyclone. Their use range is:

Mud vibrating screen: more than 74 microns

Desander: 25-40 microns

Desilter: 10-25 micron

Centrifuge: less than 10 microns

Compared to the dilution method, the method of cleaning the solid phase has the advantage that it will not increase the  volume of the drilling fluid notablely when removing the solid phase. The cost of drilling fluid was significantly decreased without the addition of a large number of processing agents.

Single type shale shaker screen and layered screen

When the single type  screen works, in order to make the shale shaker screen remove more drilling cuttings in the process of vibration, so as to reduce the working load downstream the solid control process and ensure the normal operation of the cyclone , it required that the screen mesh used by shale shaker is greater than 40 mesh. The wire diameter of these screen is less than 0.2mm, and the bearing load, wear resistance and resistance to corrosion ability is very poor. A new single screen is bad after used for only one class sometimes, the longest is only  with a few days. Frequent replacement of screen increased worker’s physical labor, increases the drilling costs, and when the screen is damaged, a large amount of sand will flows into the drilling fluid from the breakage, and make the load of subsequent solids control equipment  increase.

Shale-Shaker-Screen

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To overcome the many unfavorable factors above, in the late 1970s, the layered screen had been introduced. This kind of  screen has higher rate of liquid flow through and is not easy to lead the screen paste phenomenon of drilling fluid. Layered shaker sieve consisting of two or more layers of woven mesh overlapping structure, both the square and rectangular screen can overlap with each other, thus reducing the diameter of braided wire and increase the flow rate. The layered screen provides the sieve pore with a series of shape and size, therefore, the particle size distribution of the particles can also be wider. A layered screen is the screen fit two screen of different mesh sizes together. Usually lower for thick steel wire and small mesh screen, known for supporting net. The upper layer is a thin steel wire, large mesh screen, called the net surface. When the vibrating screen is working, the surface screen undertakes the task of screening, and the supporting screen plays the role of carrying capacity. Practice has proved that, using multilayer screen vibrating screen is effective way to improve the service life of the vibration sieve.

 

 

Mud Cleaning System designed by DC Machinery introduction

Mud cleaning system is an important and essential constituent part in the modern drilling equipment, it can keep the mud normal circle and stable performance in drilling  process, ensure drilling works on the premise of safety, environmental protection and high efficiency. On the basic of DC mud cleaning system combines the solids control advantages at home and abroad, the mud cleaning system produced byDC Machinery is mew type product which is designed by the pratical demand of drilling technology. It constituted by shale shaker, vacuum degasser, desander, desilter, centrifuge. It can realize the storage and mixture of drilling fluid, remove harmful solid phase, maintain drilling fluid performance, meet the requirements of circulation, aggravation, shearing of drilling fluid and trouble removal, efficiently improve drilling efficiency and safety. It is convenient to transport by highway and railway, and the mud cleaning system can be moved in the drilling field at a short distance.

mus-system

Quality Control System: SY/T6276, ISO/CD14690 <<Oil and gas industry health safety environmental protection and environment management system>> process flow, the equipments conform to API13C and related standard and norm.

(1) The system has humanized whole layout, beautiful appearance, strong adaptability, modern design, rational layout, perfect performance and the advanced process.

(2) The system has many good performance of cold-resistant, high temperature, anti-explosion, anti-leakage, anti-corrosion, rainnig proof, adapt to wicked condition of well drilling.

(3) There are medium pressure mud pipelines and rinsing pipelines on the tank surface.

(4) There is a pressure bar type clear sand door behind the tank, it is convenient and flexible to opened.

(5) To use the hard union type connection between the tank , it is convenient to install and teardown.

(6) Acurate positioning between the tank, and rapidly connect.

(7) The level mud solid control is high, between effect and the measurement of mud is accurate.

(8) The tanks are made of the corrugated boards of V type, the holistic rigidity is good and beautiful appearance.

(9) The tanks surface is processed by sandblasting, inner tank painted with heavy anti- corrosion bituminous paint, and outsite of the tank painted by the oil-proof and acid and alkali corrosion resistant paint.

(10) Meet the requirements of removing and installation of drilling team frequently.

(11) The system can be designed according to customers’ requirements.

 

Common malfunction of cyclone underflow on drilling mud cleaner

When the cyclone during normal operation, the air column is formed in the center of the spiral movement, resulting in a low pressure area which has a suction on the underflow. Under a certain pressure, clean water is pumped into the cyclone, and adjust the underflow orifice size until there is no liquid discharged from the underflow, and at this time size of the underflow mouth is the equilibrium point, this type of hydrocyclone are known as balance cyclone. The cyclone is most used for drilling mud cleaner, when pump the liquid containing solid into it then solid phase will be discharged from the underflow.

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Several phenomena may appear on the regulation of hydrocyclone underflow of drilling mud cleaner:

1. ‘Dry bottom': if the underflow orifice is adjusted smalller than the equilibrium point opening, a layer of dry heap shaped sand will appear between the equilibrium point and the actual underflow openings. When using this type of hydrocyclone to separate the very fine solid, the fine particles being separated lose surface water film when being through the sand layer, resulting in the underflow opening is blocked, and make the formation of “blocking”, this regulation is called “dry bottom” regulation.

2. ‘Wet bottom': if the underflow orifice is adjusted to larger than the opening of balance point, heap shaped rotating liquid will be discharged, this regulation called “wet bottom” regulation.

3. ‘Umbrella’ discharge: in the normal work, there are two fluid flowing relatively at the underflow: one is inhaled by air, another is the thick slurry containing solids that descharged as umbrella shape, then the annular barrier formed at the opening place. Inhaled air flow maintain the smooth flow of the underflow opening to ensure the cyclone working at peak efficiency.

4. ‘Rope’ discharge: when the solid content is too large in the feeding matrials, when the solid content to be separated exceeds the maximum allowable displacement of drilling mud cleaner cyclone, “overload” will generate. The underflow discharge from the bottom in a rope shape at this time. The air will not be sucked here, and there is no ring block at the opening bottom, but the formation of a choke nozzle will be made. In this case, many of the solid particles that are in the range of the clearance will be folded to the overflow pipe and return to the drilling fluid system.

The purpose and principle of screen tension

Due to the shale shaker is forced vibration screening equipment, relaxation of the screen surface will make  the effective amplitude of cuttings on the screen surface reduced, small amplitude will not be able to make cuttings jump off the screen surface, can only vibrate with the rolling screen, thus losing vibration screening and migration, resulting in talus and screen surface load increase, further increase the screening surface immunity, vicious circle. In addition if the screening process is mechanically stretched laminated screen, the slack screen surface will Produce mutual friction and beat to each other with the vibration process and debris particles are easy to be mixed in the middle of screen and grind the sieve, eventually destroying the screen mesh surface. Therefore, for the soft dough hook screen installation must be tensioning.

screens

Either way, the tension process should follow the following principles:

  1. Screen surface must be tighten and platten on the supporting spoke of screening box.
  2. Different mesh size of the screen should be applied different sizes of tension force in accordance with the instructions, pay attention to ensure the dynamic and static strength and fatigue strength of the screen.
  3. The whole screen should be forced uniformly, and to ensure that no relative motion exist between the screen and supporting spokes of the screen box ;
  4. Pay special attention that the laminated screen should have no relative sliding.

In particular, never increase the tension strength blindly without considering the strength of the screen in tightening process. due to in the process of production and processing in factories, it has been loaded with a corresponding pre tightening force between the layers of the orifice plate screen, frame type screens and wavy screen, so there is no need to the tension process above, only to ensure smooth, firmly stuck in the sieve box.

Preparation work before the start of the screw pump

1. To check whether the parts are installed in right place and if they are firm and reliable before starting the screw pump, and whether the grounding wire is firm.

2. To check if the pressure gauge of screw pump is in good condition, whether it has opened and flexible and effective (whether the pointer returning to zero).

3.To check if the motor rotation direction of screw pump is correct (to see the rotating direction on signs),  reverse rotation prohibited.

screw pump_

4. To check if the lubrication of all parts is good, the engine oil surface level is located at the place about two-thirds of the screw pump.

5. To check if tensioning force of the triangle belt on the screw pump is appropriate.

6. To check whether the safety valve of screw pump is in good condition.

7. To check whether it is clean around the screw pump, and if there is some obstructions.

The causes of cones blocking and preventive measures

The swirl funnel of drilling fluid cyclone desander and desilter will be blocked and what is the reason? How to prevent?

The main reasons are as follows:

  1. The screen of drilling fluid shale shaker selected unreasonable or drilling fluid shale shaker screen is damaged.
  2. Followed by the upper pipe of the desander and desilter is not installed with filter screen, and a large amount of particals and cuttings enter into the funnel and block the cones.
  3. During the use of solids control equipment, you must ensure that the installation location is reasonable and screen is in good condition. Install the filter screen at the place of upper pipe of desander pump and desilter pump.
  4. The swirl funnel of drilling fluid cyclone desander and desilter is not designed reasonable

SONY DSC


The drilling fluid desander produced by Tangshan Dachuan Machinery Co., Ltd. has overcome the shortcomings of the original sand removal process which is consisted of  liquid inlet pipe, row sand cone bucket and sand discharged port.

The sand discharging cone bucket  is provided with a rotating component of which the tube wall is provided with a separate window. The tube wall at the upper part of a rotating component, a group of tapered slot and the liquid inlet pipe composing drilling liquid rising component.


 

SONY DSC


The desander blades are disposed on the rotating member in the bottom and sand discharge regulator control sediment discharge.

Drilling fluid enter into the rotating component by the liquid inlet pipe and under the centrifugal rotation of blades, the sand separate from the drilling fluid when the liquid rises to split window, and then the sands discharged row sand cone bucket by split window, drilling fluid of enter into the rising component after the separation, drilling fluid enter into the drilling fluid tank by the liquid outlet of the conical groove.

The sands in the row sand cone hopper discharged from the sand discharged outlet controled by the sand control regulator.

Solids phase control and maintenance of oil based drilling fluid

Requirements for oil based drilling fluid to solid phase content is the same as the water based drilling fluid that the useless solids phase should be removed as much as possible.

Because most of the solids phase had the hydrophilic property initially, they entered into the oil based drilling mud, contacted with the oil, and then became the oil wet which will affect both stability of drilling fluid and also increase viscosity, shearing force and density of drilling fluid.

drilling-fluid


The strong inhibition of oil based drilling fluid makes it difficult to separate most of the solids phase, so it is easy to remove the solids phase with the use of solid control equipments to. The commonly used solid control equipment is shale shaker and centrifuge.

Due to the low dispersion degree of the cuttings, the effect of the shale shaker  is better than that of water based drilling mud, and the selected screen is also more finer.

The centrifuge is the only equipment that can remove the micro solids phase of the drilling mud, but because of the restrictions of its own processing capacity and the high proportion of mud and other factors, the work efficiency of centrifuge is limited.


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As the oil based drilling fluid is more expensive and with high viscosity, desander and desilter should not be used, and the influence on the aggravating materials should also be considered when using mud cleaner to separate the solids phase. Due to the inconvenience of oil based mud discharge and limited capacity of mud pool, a large number of dilution is not suitable.

Therefore, the drilling fluid that is used repeatedly should pay attention to the problem of mud aging: the methods of the precitation of solids phase and replacement of new slurry and others can be considered.

Some common fault analysis and troubleshooting of the centrifuge

1. The centrifuge and motor can not start, and the speed can not be controled.

Possible reasons

(1) Power grid of centrifuge without electricity. (2) Power supply of the centrifuge is a single phase or two phase. (3) Motor of centrifuge is damaged. (4) The time for setting up the frequency converter  is too short. (5) Frequency converter is damaged. (6) Drum and screw propeller of centrifuge is blocked with materials.

Exclusion methods

(1) Check the power supply situation of electric source. (2) Check whether the fuse wire is contacted. (3) To repair or replace the motor of centrifuge. (4) Reset the speed time of rising. (5) Check or replace the inverter of centrifuge. (6) Eliminate the accumulated materials in the drum and screw propeller.

2. Temperature of two main bearings is too high

Possible reasons

(1) Fuel quantity of bearing is too much. (2) Oil circuit is blocked up. (3) Bearing of centrifuge is damaged.

Exclusion methods

(1) Stop addding grease for 1-2 days, and run for a period of time at low or medium speed. (2) Dredge oil circuit of centrifuge and replace grease. (3) Replace  bearings of centrifuge.

Centrifuge-

3. Differential fever severely

Possible reasons

(1) It is off oil in the differential mechanism of centrifuge. (2) Bearing of differential mechanism or the parts are damaged.

Exclusion method

(1) Check the oil level and add some oil.  (2) Replace the bearing or damaged parts of centrifuge.

4. Working current is over 120A

Possible reasons

(1) The feeding rate of centrifuge is too large or the feeding is not uniform and has the impact. (2) The discharge pipe is too thin or not smooth.

Exclusion methods

(1) The feed valve shall be closed immediately. (2) Overstriking  liquid outlet pipeline and dredge the pipeline, reduce back pressure of liquid discharging.

Three types classification of mechanical agitator

The classification of mechanical agitator is divided into axial flow agitator, radial flow agitator and mixed flow agitator according to the flow pattern of the fluid. According to the structure of the impeller, the structure is divided into flat, folded, and helical surface. Representative type of mechanical agitator are mainly:

1 Paddle type agitator

Leaves of paddle type agitator are made of flat steel, being welded or fixed on the wheel hub by bolt, the leaf number is 2, 3 or 4, blade shape can be divided into two kinds of straight blade type and folding blade. The paddle type mud agitator  is mainly used for the circulation of the fluid, and also can be used for the mixing of high viscosity fluid. It can promote the exchange of upper and lower fluid, and instead the high-price screw belt impeller .

mud-agitators

2 Propulsion type agitator

The propulsion  type agitator is used in low viscosity fluid, and the turbulence of fluid is not high when mixing, but the circulating quantity is large. The propulsion type agitator is simple in structure and easy to manufacture, and is suitable for the occasions where have the low viscosity and large flow rate, and it has the good performance of the cyclic performance and the shearing action is not so good. It belongs to the circulation type agitator.

3 Turbine type agitator

The turbine type agitator belongs to the low viscosity fluid flow mixer, it is the most commonly used type of agitator in the mixing of drilling fluid. It can effectively accomplish almost all of the stirring operation, and can handle a wide range of fluid viscosity. The turbine type agitator has a large shear force, which can be used to make the fluid micelle be very fine. It is suitable for the mixing of low viscosity liquid to medium viscosity fluid and the liquid-liquid dispersion, liquid and solid suspension.