CA1153963A - Method of separation of solid phase in drilling mud - Google Patents
Method of separation of solid phase in drilling mudInfo
- Publication number
- CA1153963A CA1153963A CA000349984A CA349984A CA1153963A CA 1153963 A CA1153963 A CA 1153963A CA 000349984 A CA000349984 A CA 000349984A CA 349984 A CA349984 A CA 349984A CA 1153963 A CA1153963 A CA 1153963A
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- adhesion layer
- drilling mud
- solid phase
- particles
- drum
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Abstract
A B S T R A C T
of the Disclosure The method of separating the solid phase in a drilling mud includes forming from the drilling mud an adhesion layer on a rotated curvilinear closed surface partly projected into the drilling mud. Then a portion of this adhesion layer is se-parated onto another rotated curvilinear closed surface posi-tioned to contact a portion of the adhesion layer. The respec-tive linear speeds of the adhesion layer and of said another rotating closed curvilinear surface in the area of their con-tact are selected to be substantially equal.
of the Disclosure The method of separating the solid phase in a drilling mud includes forming from the drilling mud an adhesion layer on a rotated curvilinear closed surface partly projected into the drilling mud. Then a portion of this adhesion layer is se-parated onto another rotated curvilinear closed surface posi-tioned to contact a portion of the adhesion layer. The respec-tive linear speeds of the adhesion layer and of said another rotating closed curvilinear surface in the area of their con-tact are selected to be substantially equal.
Description
11~3~3 ~E~HOD O~ SEPARATION O~ SOLID PHASE IN DRIL~ING MUD
~ he present invention relates to borehole-drilling techni-ques, and more particularly it relates to the methods of sepa-rating the solid phase in a drilling mud.
The disclosed method can be employed to utmost effect-iveness at drilling oil, fuel gas and survey wells.
However, the disclosed method can be also efficiently employed in the chemical, pharmaceutical, metallurgical, mine-ral concentration and other industry, wherever the solid phase has to be separated or removed from a suspension.
It is commonly known that drilling mud is a heterogeneous liquid system wherein colloid-size particles of the solid pha-se are always present. The presence of these particles i8, ~rom the well-drilling quality point of view, an essential pre-requisite of adequate rheological properties of the drilling mud. The latter is expected to retain these gualities, essen-tial a they are for optimization of the well-drilling condi-tions. However, stable retaining of the essential properties of the drilling mud throughout a drilling operation has been presenting a complicated problem.
The majority o~ drilling operations are carried out in clayey roc~. The claye~ rock being drilled is partly finelg disintegrated, and the rock cuttings in the form of colloid particles get into the drilling mud.
Insufficiently effective purification of the drilling mud from rock cuttings upon several cycles of mud-pumping in the 1153~3 cour~e of a well-drilling operation has been found to 3ignifi-cantly slter the composition of the solid phase of the drilling mud, which necessitates using various methods of enhancing the drilling mud quality. Therefore, the quality purification of the drilling mud from roc~ cuttings i~ of paramount importance for the well-drilling operation.
Poor gualit~ of the purification of the drilling mud has been a ma~or cause of various emergencies and complications in-volving losses of the drilling mud, sticking of drill-pipes and casings, caving-in of rock from the borehole walls.
The technical and economic ratings of a drilling operat-ion are greatly influenced by the quality of the drilling mud used, as well as by the degree of its purification from rock cuttings.
~ uality purification of the drilling mud helps getting a w~ll down faster, owing to the reduced content of the solid phase in the liquid one, and enhances the working environment of the bits and down-hole tools. Apart from stepping up the mechanical rate of drilling, guality purification of the drill-ing mud helps reducing the consumption of the materials spent on maintaining the required properties of the drilling mud, prolonging the life of the mud, avoiding emergencies and com-plications of the drilling operation.
In short, quality puirification of the drilling mud from roc~ cuttings is an essential process of the well-drilli~g ope-ration, significantly influencing the operation's technical and economic ratings.
1~5~63 All the hitherto known tachniques of puri~ing drilling muds enable to remove frDm tbe circulating mud a certain pro-portiDn of solid particles with a certain degree Df efficiencD
and quality.
Thus, the minimum size of particles that can be separat-ed from a drilling mud on vibrates sieves is defined by the mesh size of the sieve. With the finer mesh used to enhance the quality of the punfication, the pass-through capability of the sieve becDmes seriously affected, and the 1DSS of the drilling mud with the sludge is stepped up.
When purified in hydrocyclones, the drilling mud is di-luted with water, and particles of a relatively high density are predDminantly removed therefrom. The finer or less dense particles which becvme resident in the drilling mud as rock cutti~gs become dispersed therein would not be removed in hyd-rocyclones and numerous other purification devices currently in use.
~ hers is known a method of regeneration of a stable clayeg suspension of a drilling mud, according to which the drilling mud coming from the well and containing rock cuttings is pre-diluted with water and has greater particles removed therefrom.
~he thus diluted and precleaned drilling mud cDntains fin7un-charged particles of cut rDck and negatively charged cDll~id--size particle~of clay. Then the negatively charged particles of clay are separated from the mud by being depDsited on a ro-tating anode and subsequently removed with a æcraper tDol, the settling negatively charged particles of clay entraining there-~1~3~63 ~ith some of the uncharged particles which are li~ewise de-posited on the rotating anode.
~ he abovedescribed method is used to purify but a portion of the total flow of the drilling mud, while the far greater remaining portion of the mud is recirculated into the well in an uncleaned state. Furthermore, the stagewise purification, first, from the coarser particles, and, then, from the ~iner one is complicated and, hence, costl~.
It is an object of the present invention to create a method of separating the solid phase in a drilling mud, which should provide for purifying the entire volume of the drilling mud coming from a well in a relatively simple operation.
It is another object of the present invention to reduce the cost of purification of the drilling mud.
It is a further object of the present invention to provide for higher drill~ng rates, owing to the improved quality of the purification of the drilling mud.
With these an other objects in view, there is hereby disclosed a method of separation of a solid phase in a drill-ing mud~ which in accordance with the present invention, com-prises forming an adhesion layer from the drilling mud on a curvilinear closed surface partly projecting into the drill-ing mud and being rotated, and separating a portion of said lay-er onto another rotating curvilinear closed surface positioned to contact a portion of the adhesion layer, the linear speeds o~ the adhesion layer and of the other rotating closed curvilinear surface in the area of their contact being selected to be sub-stantially egual.
It is expedient to have separated onto the other curvili~-ear closed surface the portion of the adhesion layer, rich in the coarser particles of the solid phase.
The above technique can be used for separating the adhe-sion layer formed on the external side of a rotating c~rvilinear closed surface. ~his enables to conduct the process of separat-ing the solid phase in a drilling mud by regulating the ~alue of the linear speed of the outer surface of the adhesion layer, and thus regulating the separation from the adhesion layer of solid particles having the density in excess of the density of the drilling mud from which the adhesion layer is formed.
It is also possible to separate onto the other curvilinear closed surface the portion of the adhesion layer, cleaned from the coarser-particles of the solid phase.
This technique can be used for separating the adhesion layer formed on the internal side of a rotating curvilinear closed surface.
This enables to conduct the process of separating the solid phase in the drilling mud by regulating the value of the linear speed of the inner surface of the adhesion layer and that of the other curvilinear closed surface in the sense of stepping up this value~ and thus regulating the separation from the adhesion layer of the particles of the solid phase of the drilling mud.
~ 3~63 It is not lesæ expedient to vary the value of the surface tension of the adhesion layer, while separating the solid phase of the drilling mud.
The variation of the surface tension of the adhesion layer facilitates separation of solid particles therefrom.
It is further ex~edient to vary the surface tension of the adhesion layer by acting thereupon with a direct-current elec-tric field.
By passing an electric current through the area of separa-tion of the particles of the solid phase from the adhesion layer, the value of the surface tension is reduced, owing to an in-creased concentration of electrically charged particles in the surface layer. The reduced value of the surface tension of the adhesion layer of the drilling mud further enhances the condi-tions of separation of the solid phase of the drilling mud.
It is not less expedient to vary the value of the surface tension of the adhesion layer by altering the direction of the electric current in accordance with the mineralogic composi-tion of the solid phase of the drilling mud.
Th~ above technique enables to intensify the selective character of the removal of the solid phase. The feeding of a positive potential to the other curvilinear closed surface re-sults in more efficient removal from the adhesion layer of the drilling mud of negatively charged particles of clay, a~ com-pared with the removal in the absence of the electric field.
On the other hand, the feeding of a negative potential to the liS3~63 other curvilinear closed surface intensifies the removal from the adhesion layer of the drilling mud of neutral get heavy particles, e.g. barite ones, and of positively charged mineral particles.
It ma~ be expedient to vary the value of the surface ten-sion of the adhesion layer by varying the intensity of the electric field in accordance with the particle size distribu-tion in the solid phase of the drilling mud.
This technique broadens still further the range of con-trol of the removal of the solid phase from a drilling mud.
Thus, by performing the withdrawal of the solid phase of the drilling mud by the other rotating curvilinear closed sur-face from the formed adhesion layer, while making a controll_ able electric current flow through the withdrawal area, and varying the polarit~ of the electric current, there is ensured efficient control of the process of separating the solid phase of the drilling mud within a broad range, according to the mi-neralogic composition of thiæ phase. The separation of the so-lid phase i~ carried out in a simple and economic operation offering a high throughput.
Given below is a description of an embodiment of the pre-sent invention, with reference being made to the accompanying drawings, wherein:
~ ig. 1 illustrates schematically individual portions of the adhesion layer of the drilling mud, formed on the external side of a rotating cylindrical surface;
11~3~63 ~ ig. 2 illustrates schematically individual portions of the adhesion layer of the drilling mud, formed on the internal side of a rotating cylindrical surface.
Referring now to the drawings, the method of separating the solid phase in a drilling mud includes forming from the drilling mud l (FIG. l) an adhesion layer 2 on a rotating cur-vilinear closed surface 3.
In the embodiment being described this cylindrical surfa-ce is that of a drum 4 associated with a drive (not shown) for rotating the drum 4. The drum 4 is mounted so that a portion of its surface 3 projects into the drilling mud l. In the course of the rotation, a portion of the adhesion layer 2 (by the depth thereof) is separated onto another curvilinear closed surface 5 which in the presently described embodiment is that of an auxiliary drum 6 operatively connected with a dri~e (not shown) for rotating this drum 6. ~he angular speeds of the ro-tating drums 4 and 6 are selected for their linear speeds in the area of contact of the adhesion layer 2 and of the other curvilinear clo~ed surface 5 to be substantially equal.
~ he equality of the linear speeds provides for gradual stratification of the adhesion layer 2 into two portions with different contents of the solid phase particles.
; The thickness of the formed adhesion layer 2 of the drill-ing mud l depends on the ~iscosity of the drilling mud l and on the speed of the rotation of the drum 4. The adhesion layer
~ he present invention relates to borehole-drilling techni-ques, and more particularly it relates to the methods of sepa-rating the solid phase in a drilling mud.
The disclosed method can be employed to utmost effect-iveness at drilling oil, fuel gas and survey wells.
However, the disclosed method can be also efficiently employed in the chemical, pharmaceutical, metallurgical, mine-ral concentration and other industry, wherever the solid phase has to be separated or removed from a suspension.
It is commonly known that drilling mud is a heterogeneous liquid system wherein colloid-size particles of the solid pha-se are always present. The presence of these particles i8, ~rom the well-drilling quality point of view, an essential pre-requisite of adequate rheological properties of the drilling mud. The latter is expected to retain these gualities, essen-tial a they are for optimization of the well-drilling condi-tions. However, stable retaining of the essential properties of the drilling mud throughout a drilling operation has been presenting a complicated problem.
The majority o~ drilling operations are carried out in clayey roc~. The claye~ rock being drilled is partly finelg disintegrated, and the rock cuttings in the form of colloid particles get into the drilling mud.
Insufficiently effective purification of the drilling mud from rock cuttings upon several cycles of mud-pumping in the 1153~3 cour~e of a well-drilling operation has been found to 3ignifi-cantly slter the composition of the solid phase of the drilling mud, which necessitates using various methods of enhancing the drilling mud quality. Therefore, the quality purification of the drilling mud from roc~ cuttings i~ of paramount importance for the well-drilling operation.
Poor gualit~ of the purification of the drilling mud has been a ma~or cause of various emergencies and complications in-volving losses of the drilling mud, sticking of drill-pipes and casings, caving-in of rock from the borehole walls.
The technical and economic ratings of a drilling operat-ion are greatly influenced by the quality of the drilling mud used, as well as by the degree of its purification from rock cuttings.
~ uality purification of the drilling mud helps getting a w~ll down faster, owing to the reduced content of the solid phase in the liquid one, and enhances the working environment of the bits and down-hole tools. Apart from stepping up the mechanical rate of drilling, guality purification of the drill-ing mud helps reducing the consumption of the materials spent on maintaining the required properties of the drilling mud, prolonging the life of the mud, avoiding emergencies and com-plications of the drilling operation.
In short, quality puirification of the drilling mud from roc~ cuttings is an essential process of the well-drilli~g ope-ration, significantly influencing the operation's technical and economic ratings.
1~5~63 All the hitherto known tachniques of puri~ing drilling muds enable to remove frDm tbe circulating mud a certain pro-portiDn of solid particles with a certain degree Df efficiencD
and quality.
Thus, the minimum size of particles that can be separat-ed from a drilling mud on vibrates sieves is defined by the mesh size of the sieve. With the finer mesh used to enhance the quality of the punfication, the pass-through capability of the sieve becDmes seriously affected, and the 1DSS of the drilling mud with the sludge is stepped up.
When purified in hydrocyclones, the drilling mud is di-luted with water, and particles of a relatively high density are predDminantly removed therefrom. The finer or less dense particles which becvme resident in the drilling mud as rock cutti~gs become dispersed therein would not be removed in hyd-rocyclones and numerous other purification devices currently in use.
~ hers is known a method of regeneration of a stable clayeg suspension of a drilling mud, according to which the drilling mud coming from the well and containing rock cuttings is pre-diluted with water and has greater particles removed therefrom.
~he thus diluted and precleaned drilling mud cDntains fin7un-charged particles of cut rDck and negatively charged cDll~id--size particle~of clay. Then the negatively charged particles of clay are separated from the mud by being depDsited on a ro-tating anode and subsequently removed with a æcraper tDol, the settling negatively charged particles of clay entraining there-~1~3~63 ~ith some of the uncharged particles which are li~ewise de-posited on the rotating anode.
~ he abovedescribed method is used to purify but a portion of the total flow of the drilling mud, while the far greater remaining portion of the mud is recirculated into the well in an uncleaned state. Furthermore, the stagewise purification, first, from the coarser particles, and, then, from the ~iner one is complicated and, hence, costl~.
It is an object of the present invention to create a method of separating the solid phase in a drilling mud, which should provide for purifying the entire volume of the drilling mud coming from a well in a relatively simple operation.
It is another object of the present invention to reduce the cost of purification of the drilling mud.
It is a further object of the present invention to provide for higher drill~ng rates, owing to the improved quality of the purification of the drilling mud.
With these an other objects in view, there is hereby disclosed a method of separation of a solid phase in a drill-ing mud~ which in accordance with the present invention, com-prises forming an adhesion layer from the drilling mud on a curvilinear closed surface partly projecting into the drill-ing mud and being rotated, and separating a portion of said lay-er onto another rotating curvilinear closed surface positioned to contact a portion of the adhesion layer, the linear speeds o~ the adhesion layer and of the other rotating closed curvilinear surface in the area of their contact being selected to be sub-stantially egual.
It is expedient to have separated onto the other curvili~-ear closed surface the portion of the adhesion layer, rich in the coarser particles of the solid phase.
The above technique can be used for separating the adhe-sion layer formed on the external side of a rotating c~rvilinear closed surface. ~his enables to conduct the process of separat-ing the solid phase in a drilling mud by regulating the ~alue of the linear speed of the outer surface of the adhesion layer, and thus regulating the separation from the adhesion layer of solid particles having the density in excess of the density of the drilling mud from which the adhesion layer is formed.
It is also possible to separate onto the other curvilinear closed surface the portion of the adhesion layer, cleaned from the coarser-particles of the solid phase.
This technique can be used for separating the adhesion layer formed on the internal side of a rotating curvilinear closed surface.
This enables to conduct the process of separating the solid phase in the drilling mud by regulating the value of the linear speed of the inner surface of the adhesion layer and that of the other curvilinear closed surface in the sense of stepping up this value~ and thus regulating the separation from the adhesion layer of the particles of the solid phase of the drilling mud.
~ 3~63 It is not lesæ expedient to vary the value of the surface tension of the adhesion layer, while separating the solid phase of the drilling mud.
The variation of the surface tension of the adhesion layer facilitates separation of solid particles therefrom.
It is further ex~edient to vary the surface tension of the adhesion layer by acting thereupon with a direct-current elec-tric field.
By passing an electric current through the area of separa-tion of the particles of the solid phase from the adhesion layer, the value of the surface tension is reduced, owing to an in-creased concentration of electrically charged particles in the surface layer. The reduced value of the surface tension of the adhesion layer of the drilling mud further enhances the condi-tions of separation of the solid phase of the drilling mud.
It is not less expedient to vary the value of the surface tension of the adhesion layer by altering the direction of the electric current in accordance with the mineralogic composi-tion of the solid phase of the drilling mud.
Th~ above technique enables to intensify the selective character of the removal of the solid phase. The feeding of a positive potential to the other curvilinear closed surface re-sults in more efficient removal from the adhesion layer of the drilling mud of negatively charged particles of clay, a~ com-pared with the removal in the absence of the electric field.
On the other hand, the feeding of a negative potential to the liS3~63 other curvilinear closed surface intensifies the removal from the adhesion layer of the drilling mud of neutral get heavy particles, e.g. barite ones, and of positively charged mineral particles.
It ma~ be expedient to vary the value of the surface ten-sion of the adhesion layer by varying the intensity of the electric field in accordance with the particle size distribu-tion in the solid phase of the drilling mud.
This technique broadens still further the range of con-trol of the removal of the solid phase from a drilling mud.
Thus, by performing the withdrawal of the solid phase of the drilling mud by the other rotating curvilinear closed sur-face from the formed adhesion layer, while making a controll_ able electric current flow through the withdrawal area, and varying the polarit~ of the electric current, there is ensured efficient control of the process of separating the solid phase of the drilling mud within a broad range, according to the mi-neralogic composition of thiæ phase. The separation of the so-lid phase i~ carried out in a simple and economic operation offering a high throughput.
Given below is a description of an embodiment of the pre-sent invention, with reference being made to the accompanying drawings, wherein:
~ ig. 1 illustrates schematically individual portions of the adhesion layer of the drilling mud, formed on the external side of a rotating cylindrical surface;
11~3~63 ~ ig. 2 illustrates schematically individual portions of the adhesion layer of the drilling mud, formed on the internal side of a rotating cylindrical surface.
Referring now to the drawings, the method of separating the solid phase in a drilling mud includes forming from the drilling mud l (FIG. l) an adhesion layer 2 on a rotating cur-vilinear closed surface 3.
In the embodiment being described this cylindrical surfa-ce is that of a drum 4 associated with a drive (not shown) for rotating the drum 4. The drum 4 is mounted so that a portion of its surface 3 projects into the drilling mud l. In the course of the rotation, a portion of the adhesion layer 2 (by the depth thereof) is separated onto another curvilinear closed surface 5 which in the presently described embodiment is that of an auxiliary drum 6 operatively connected with a dri~e (not shown) for rotating this drum 6. ~he angular speeds of the ro-tating drums 4 and 6 are selected for their linear speeds in the area of contact of the adhesion layer 2 and of the other curvilinear clo~ed surface 5 to be substantially equal.
~ he equality of the linear speeds provides for gradual stratification of the adhesion layer 2 into two portions with different contents of the solid phase particles.
; The thickness of the formed adhesion layer 2 of the drill-ing mud l depends on the ~iscosity of the drilling mud l and on the speed of the rotation of the drum 4. The adhesion layer
2 contains solid particles of rock cuttings, the weighting ma-1~3~3 terial and the clayey solid phase. With the drum 4 rotating, the action of the cent~fugal forces results in redistribution of the solid particles in accordance with their densit~ and volume, with the coarser and heavier particles migrating toward the outer surface of the adhesion lager 2, and the finer par-ticles, particucarlg, the colloid-size ones, remaining closer to the lnner surface of this adhesion layer 2.
The speed of rotating the auxiliary drum 6 is set at a value providing for synchronous rotation of the surface 5 of the auxiliary drum 6 and of the outer surface of the adhesion layer 2.
The drums 4 and 6 are mounted for the gap between their respective peripheries to be not less than the thic~ness of the adhesion layer 2.
A solid phase particle within the adhesion layer 2 has act-ing thereon, on the one hand, centrifugal forces ~ mV (l) R
where "m" i8 the mass of the aprticle, "R" is the radius of the circle of its rotation, "V" is the linear speed of its rotation;
and, on the other hand, it has acting thereon its weight or gravity force, viscous friction forces and the forces "~1" f the surface tension of the adhesion layer 2:
Fl = 2 ~r ~ ~ (2) _ 10 --~here "r" is the radius of the particle of the solid phase of the drilling mud;
"~" is the surface tension coefficient of the drilling mud 1.
The evaluation of the relative significance of the forces taking part in the distribution of the solid particles in the surface layer can be made by using the ~roude cryterion or similarity nu~ber characterizing the ratio of the centrifugal forces to the forces of gravity:
Fr =c~ ~ , (3~
where "~ " is the angular speed of the rotation of the drum 4, and "R" i8 the radius of the circle of rota-tion of the particle, while "g" is the gravity acceleration.
It is knownthat the minimum and maximum values of the ~roude similaritg number for real-life structures are within a range from 20 to 2000.
It can be derived from the-abovesaid that in the calcula-tion of the forces acting upon the solid particles in the ad-hesion layer 2 their weight may be neglected for practical re-asons, as long as the centrifugal forces are 20 to 2000 times greater. Since the friction force between the surface of the solid phase particles and the liquid entraining them for rota-li~39~3 tion is directed tangentially to the surface of the drum 4and perpendicularly to its radius, the peculiarities of the radial motion of the particles, i.e. the ma~or laws governing the process of the separation of the phases and fractions (the purification process) may be considered without providing for the viscous friction forces.
Th~s, by presuming the equality of the forces "~" and "Fl", it is possible to arrive at the condition of eguilibrium of the particles in the adhesion lsyer 2 formed on the cylin-drical surface 3 of the rotating drum 4:
6 ( ~1 ~2) ~ R = 2 ~ r~ = ~d~ t4) or else, it can be e~pressed in relation to the diameter of the particle (which latter is conditionally taken to be spherical):
d V 6~ (5) 2) ~R
where "~1" and "~2" are, respectively, the densities of the solid phase and of the liguid;
"d" is the diameter of the particle (d=2r);
'1R" is the radius of the circle of rotation of the par-ticles;
" ~" is the surface ten~ion coefficient of the liguid of the adhesion layer.
:1~53~3 It can be seen from expressions (4) and (5) that the motion of a particle of the diameter "d" in the adhesion lager 2 depends on the density of the drilling mud l1 the radius "R" of the circle of rotation of this particle, the speed of its rotation and the value of the surface tension of the adhesion layer 2. The radius of the circle of rotatio~
of the particle is defined by the diameter of the drum 4. Ho-wever, you cannot increase substantially the diameter of the drum 4 without encountering corresponding complexity of its manufacturing and mounting. Therefore, the major parameters of the process of separation of the solid phase of the drill-ing mud l on the rotating cylindrical surface 3 are the speed of the rotation of the drum 4 and the value of the surface tension of the adhesion layer 2.
As a result of the contact between the surface 5 of the auxiliar~ drum 6 and the adhesion layer 2, a portion of the last-mentioned layer becomes separated and taken by this sur-face.
Depending on the relative positions of the drums 4 and 6, the separated portion of the adhesion layer 2 contains dif-ferent concentrations of the solid phase.
When the adhesion layer 2 is formed on the external surfa-ce of the drum 4 (~ig. l), the auxiliary drum 6 takes up the portion of the adhesion layer 4, enriched in the coarser heavy particles of the solid phase of the drilling mud l. This por-tion 7 of the adhesion layer 2 is directed by the scraper 8 into a trough 9.
il53~3 Whe~ the adhesion layer 10 (Fig. 2) is formed on the inter-nal surface 11 of a drum 12, the other closed curvilinear sur-face 13, i.e. that of the auxiliary drum 13a takes up the por-tion 14 of the adhesion layer 10, cleaned from the coarser and heavier particles of the solid phase of the drilling mud 1. In other words, the taken-up portion 14 of the adhesion layer 10 ha~ been purified from the coarser particles of the solid pha-se of the drilling mud 1. A scraper 15 removes the portion 14 off the surface of the auxiliary drum 13a and direct~ it into a trough 16.
Particles of the solid phase projected from the portion 14 of the adhesion layer 10 by the centrifugal forces are in-tercepted by a guard 17, and flow down this guard 17 into the trough 16.
To enhance the efficiency of the separation of the solid phase of the drilling mud, the value of the surface tension of the adhesion layer is varied bg acting thereupon with a direct-current electric field. The electric current flows ~ia the cir-cuit: current source 18 (~IGS. 1 and 2) - drum 4 (12) - adhe-sion layer 2 (10) - augiliary drum 6 (13a). With a positive potential fed to the auxiliary drum 6 (13a), the separation of negatively charged colloid particles is intensi~ied, whereas with the polarity reversed, more neutral and positively charged particles are separated on the auxiliary drum 6 (13a).
Depending on the particle size, or fraction content of the solid phase o~ the drilling mud, the value of the surface 1~3~3 tension of the adhesion layer i8 controlled by varying the in-tensity of the electric field.
To remove the weighting material, the drilling mud 1 containing ~olid roc~ cuttings is disintegrated prior to the separation to the size of the weighting material particles.
This speeds up the separation of the particles of the weight-ing material which are of a density at least twice as great as that of rock cuttings.
The portion of the adhesion layer 2 (10), remaining on the drum 4 (12) after the separation of its portion 7 (14~ by the aux~liary drum 6 (13a), is scraped off by a scraper 19 (~IG. 1) and directed into a receptacle 20. By controlling the speed of rotation of the drum 4 (12) and the value of the surface tension of the adhesion layer 2 (10) by varying the value and the polarity (or direction) of the electric current, it is possible to regulate the separation of the solid phase in the drilling mud within a broad range, to remove the excessi-ve solid phase a~d to retain the fine particles of clay which make up the major colloid-size component of the drilling mud.
The herein disclosed method is performed, as follows.
Following feeding the drilling mud 1 into a vessel 21 (FIG. 1), the drive (not shown) o~ the drum 4 is energized. As a result of the contact between the surface 3 of the drum 4 and the drilli~g mud 1, there is formed on the surface 3 the adhe-sion layer 2. The angular speed of the drum 4 i9 set to cor-respond to the ~iscosity of the drilling mud 1 and the required llt~3~fi3 d~3gree of its purification. The gap between the respective pe-ripheries of the drums 4 and 6 is adjusted to correspond to the thickness (or depth) of the adhesion layer 2. The speed of rotation of the auxiliary drum 6 is set to a value providing for equality of the linear speeds of the surface of the rotat-ing auxiliary drum and of the outer surface of the adhesion layer 2. ~he required polarity of the electric current fed to the drums 4 and 6 from the direct-current source 18 is set to correspond to the mineralogic composition of the sludge in the drilling mud 1.
By gradually varying the value of the electric current, the required degree of the purification of the drilling mud 1 i8 attained.
Thus, the herein disclosed method of centrifugal separ-ation of the solid phase of the drilling mud 1 in electric fields of alternati~e polarity on rotating curvilinear closed surfaces 3, 5 e~ables to control within a broad range the amount of the solid phase and the size of the particles being separated, up to complete clarification of the liouid, which cannot be attained by using any of the hitherto known methods.
As an example of the implementation of the herein dis-closed method, it is possible to supply the data obtained in the study aimed at determining the optimum parameters of the duty of purifying the drilling mud 1 from sludge taken off the surface of the adhe9ion layer ~ formed on the surface 3 of the drum 4.
1~3~63 - 16 _ Drums of various diameters from 100 to 500 mm were tested as the main drum 4, and were rotated at 10 r.p.m. to 10,000 r.p.m. The tested auxiliary drums 5 has similar param-eters.
It was found that with the main drum 4 rotated at a speed from 10 r.p.m. to 150-200 r.p.m., thethickness of the adhesion layer 2 formed from the drilling mud 1 of a viscosity from 10 to 100 centipoise was 1.5 to 3 mm. The small thickness of the adhesion layer 2 was in these cases caused by the liquid flow-ing and drippin down from the surface of the drum 4 rotated at a low speed. This thickness of the adhesion layer 2 would not provide for reguired productivity of the drum 4.
Within the range of the speeds of rotation from 200 to 500 r.p.m. the thickness of the adhesion layer 2 on the sur-face 3 of the drum 4, with the drilling mud 1 viscosity from 10 to 100 centipoise, varied between 3 and 8 mm, and the solid particles of diameters between 0.8 and 4 mm where separated from the sur~ace of the adhesion layer 2. All the particles of the diameters short of the abovementioned ones remained within the adhesion layer.
The study has shown that the angular speed of the surface of the adhesion layer 2, contacting the ambient air, is signif-icantly lower (10 to 30 times) than the angular speed of the surface 3 of the drum 4. On account of this phenomenon, with the drum 4 rotated at speeds from 1000 and 2000 r.p.m., which are the optimum ones from the theoretical calculation made on 1153~63 the assumption that the adhesion layer 2 rigidl~ rotate~ with the drum 4, the particles of the solid phase of the minimum size of 0.07 mm cannot be separated to the required degree of purification.
If, however, the surface lager of the liguid is driven at the speed equalling the speed of rotation of the drum 4 by the action o~ the auxiliary drum 6, the theoretical calculation of the purification degree is completely sustained. When voltage .
of alternative polarity was fed to the drums 4 and 6 from the direct-c~rrent source 8, the fineness and degree of the purifi-cation were enhanced, owing to the reduced surface tension of the adhesion layer, with the minimum size of the solid phase particles removed from the adhesion layer being 20 microns.
It was found that a potential corresponding to the charge of the sludge particles, or rock cuttings had to be fed to the drum 4 while purifying drilling muds. Thus, if the sludge is represented by negatively charged particles of clay, a nega-tive potential is preferably fed to the drum 4, whereas with the sludge being represented by positively charged calcite particles, it is a positive potential that pre~erably has to be fed to the drum 4.
The studies also proved that to attain quality purificat-ion of drilling muds of viscosities from lO to lO0 cent.ipoise (to the minimum size of the removed particles egualling 20 mic-rons), it was necessary to rotate the drum 4 at speeds from , : :
1~$3963 1000 to 2000 ~.p.m. and to feed to the drum 4 the voltage of 10 to 20 V.
Thus, to purify the relatively clear drilling mud (30 to 40~0 solid phase) with the maximum size of the ~olid particles up to 200 - 300 microns, the diameter of the main drum was selected to be 420 to 500 mm, and the speed of its rotation was set at 1800 to 2000 r.p.m. The diameter of the auxiliary drum 6 was preferably 140 to 160 mm, and the speed of its ro-tation was set at 5000 to 6000 r.p.m. Under such conditions solid particles as small as I2 to 16 microns were separated from the adhesion layer.
It was further found that when the drilling mud with a high content of sludge and the size of the solid particles in excess of 1 mm had to be purified, the diameter of the main drum ~as preferably 100 to 120 mm, and the speed of its rota-tion was 1000 to 1200 r.p.m. The auxiliary drum diameter was preferab b from 30 to 40 mm, and the speed of its rotation was 3000 to 3600 r.p.m, Solid particles of a size from 40 to 50 microns were separated from the adhesion layer 2.
The economic effectiveness of the ~rein disclosed method of separating the solid phase in a drilling mud is made up of the reduced purification costs, owing to getting rid of a multis-tage purification system, of the prolonged life of the drilling mud and of faster drilling, due to the enhanced purification guality of the drilling mud.
The speed of rotating the auxiliary drum 6 is set at a value providing for synchronous rotation of the surface 5 of the auxiliary drum 6 and of the outer surface of the adhesion layer 2.
The drums 4 and 6 are mounted for the gap between their respective peripheries to be not less than the thic~ness of the adhesion layer 2.
A solid phase particle within the adhesion layer 2 has act-ing thereon, on the one hand, centrifugal forces ~ mV (l) R
where "m" i8 the mass of the aprticle, "R" is the radius of the circle of its rotation, "V" is the linear speed of its rotation;
and, on the other hand, it has acting thereon its weight or gravity force, viscous friction forces and the forces "~1" f the surface tension of the adhesion layer 2:
Fl = 2 ~r ~ ~ (2) _ 10 --~here "r" is the radius of the particle of the solid phase of the drilling mud;
"~" is the surface tension coefficient of the drilling mud 1.
The evaluation of the relative significance of the forces taking part in the distribution of the solid particles in the surface layer can be made by using the ~roude cryterion or similarity nu~ber characterizing the ratio of the centrifugal forces to the forces of gravity:
Fr =c~ ~ , (3~
where "~ " is the angular speed of the rotation of the drum 4, and "R" i8 the radius of the circle of rota-tion of the particle, while "g" is the gravity acceleration.
It is knownthat the minimum and maximum values of the ~roude similaritg number for real-life structures are within a range from 20 to 2000.
It can be derived from the-abovesaid that in the calcula-tion of the forces acting upon the solid particles in the ad-hesion layer 2 their weight may be neglected for practical re-asons, as long as the centrifugal forces are 20 to 2000 times greater. Since the friction force between the surface of the solid phase particles and the liquid entraining them for rota-li~39~3 tion is directed tangentially to the surface of the drum 4and perpendicularly to its radius, the peculiarities of the radial motion of the particles, i.e. the ma~or laws governing the process of the separation of the phases and fractions (the purification process) may be considered without providing for the viscous friction forces.
Th~s, by presuming the equality of the forces "~" and "Fl", it is possible to arrive at the condition of eguilibrium of the particles in the adhesion lsyer 2 formed on the cylin-drical surface 3 of the rotating drum 4:
6 ( ~1 ~2) ~ R = 2 ~ r~ = ~d~ t4) or else, it can be e~pressed in relation to the diameter of the particle (which latter is conditionally taken to be spherical):
d V 6~ (5) 2) ~R
where "~1" and "~2" are, respectively, the densities of the solid phase and of the liguid;
"d" is the diameter of the particle (d=2r);
'1R" is the radius of the circle of rotation of the par-ticles;
" ~" is the surface ten~ion coefficient of the liguid of the adhesion layer.
:1~53~3 It can be seen from expressions (4) and (5) that the motion of a particle of the diameter "d" in the adhesion lager 2 depends on the density of the drilling mud l1 the radius "R" of the circle of rotation of this particle, the speed of its rotation and the value of the surface tension of the adhesion layer 2. The radius of the circle of rotatio~
of the particle is defined by the diameter of the drum 4. Ho-wever, you cannot increase substantially the diameter of the drum 4 without encountering corresponding complexity of its manufacturing and mounting. Therefore, the major parameters of the process of separation of the solid phase of the drill-ing mud l on the rotating cylindrical surface 3 are the speed of the rotation of the drum 4 and the value of the surface tension of the adhesion layer 2.
As a result of the contact between the surface 5 of the auxiliar~ drum 6 and the adhesion layer 2, a portion of the last-mentioned layer becomes separated and taken by this sur-face.
Depending on the relative positions of the drums 4 and 6, the separated portion of the adhesion layer 2 contains dif-ferent concentrations of the solid phase.
When the adhesion layer 2 is formed on the external surfa-ce of the drum 4 (~ig. l), the auxiliary drum 6 takes up the portion of the adhesion layer 4, enriched in the coarser heavy particles of the solid phase of the drilling mud l. This por-tion 7 of the adhesion layer 2 is directed by the scraper 8 into a trough 9.
il53~3 Whe~ the adhesion layer 10 (Fig. 2) is formed on the inter-nal surface 11 of a drum 12, the other closed curvilinear sur-face 13, i.e. that of the auxiliary drum 13a takes up the por-tion 14 of the adhesion layer 10, cleaned from the coarser and heavier particles of the solid phase of the drilling mud 1. In other words, the taken-up portion 14 of the adhesion layer 10 ha~ been purified from the coarser particles of the solid pha-se of the drilling mud 1. A scraper 15 removes the portion 14 off the surface of the auxiliary drum 13a and direct~ it into a trough 16.
Particles of the solid phase projected from the portion 14 of the adhesion layer 10 by the centrifugal forces are in-tercepted by a guard 17, and flow down this guard 17 into the trough 16.
To enhance the efficiency of the separation of the solid phase of the drilling mud, the value of the surface tension of the adhesion layer is varied bg acting thereupon with a direct-current electric field. The electric current flows ~ia the cir-cuit: current source 18 (~IGS. 1 and 2) - drum 4 (12) - adhe-sion layer 2 (10) - augiliary drum 6 (13a). With a positive potential fed to the auxiliary drum 6 (13a), the separation of negatively charged colloid particles is intensi~ied, whereas with the polarity reversed, more neutral and positively charged particles are separated on the auxiliary drum 6 (13a).
Depending on the particle size, or fraction content of the solid phase o~ the drilling mud, the value of the surface 1~3~3 tension of the adhesion layer i8 controlled by varying the in-tensity of the electric field.
To remove the weighting material, the drilling mud 1 containing ~olid roc~ cuttings is disintegrated prior to the separation to the size of the weighting material particles.
This speeds up the separation of the particles of the weight-ing material which are of a density at least twice as great as that of rock cuttings.
The portion of the adhesion layer 2 (10), remaining on the drum 4 (12) after the separation of its portion 7 (14~ by the aux~liary drum 6 (13a), is scraped off by a scraper 19 (~IG. 1) and directed into a receptacle 20. By controlling the speed of rotation of the drum 4 (12) and the value of the surface tension of the adhesion layer 2 (10) by varying the value and the polarity (or direction) of the electric current, it is possible to regulate the separation of the solid phase in the drilling mud within a broad range, to remove the excessi-ve solid phase a~d to retain the fine particles of clay which make up the major colloid-size component of the drilling mud.
The herein disclosed method is performed, as follows.
Following feeding the drilling mud 1 into a vessel 21 (FIG. 1), the drive (not shown) o~ the drum 4 is energized. As a result of the contact between the surface 3 of the drum 4 and the drilli~g mud 1, there is formed on the surface 3 the adhe-sion layer 2. The angular speed of the drum 4 i9 set to cor-respond to the ~iscosity of the drilling mud 1 and the required llt~3~fi3 d~3gree of its purification. The gap between the respective pe-ripheries of the drums 4 and 6 is adjusted to correspond to the thickness (or depth) of the adhesion layer 2. The speed of rotation of the auxiliary drum 6 is set to a value providing for equality of the linear speeds of the surface of the rotat-ing auxiliary drum and of the outer surface of the adhesion layer 2. ~he required polarity of the electric current fed to the drums 4 and 6 from the direct-current source 18 is set to correspond to the mineralogic composition of the sludge in the drilling mud 1.
By gradually varying the value of the electric current, the required degree of the purification of the drilling mud 1 i8 attained.
Thus, the herein disclosed method of centrifugal separ-ation of the solid phase of the drilling mud 1 in electric fields of alternati~e polarity on rotating curvilinear closed surfaces 3, 5 e~ables to control within a broad range the amount of the solid phase and the size of the particles being separated, up to complete clarification of the liouid, which cannot be attained by using any of the hitherto known methods.
As an example of the implementation of the herein dis-closed method, it is possible to supply the data obtained in the study aimed at determining the optimum parameters of the duty of purifying the drilling mud 1 from sludge taken off the surface of the adhe9ion layer ~ formed on the surface 3 of the drum 4.
1~3~63 - 16 _ Drums of various diameters from 100 to 500 mm were tested as the main drum 4, and were rotated at 10 r.p.m. to 10,000 r.p.m. The tested auxiliary drums 5 has similar param-eters.
It was found that with the main drum 4 rotated at a speed from 10 r.p.m. to 150-200 r.p.m., thethickness of the adhesion layer 2 formed from the drilling mud 1 of a viscosity from 10 to 100 centipoise was 1.5 to 3 mm. The small thickness of the adhesion layer 2 was in these cases caused by the liquid flow-ing and drippin down from the surface of the drum 4 rotated at a low speed. This thickness of the adhesion layer 2 would not provide for reguired productivity of the drum 4.
Within the range of the speeds of rotation from 200 to 500 r.p.m. the thickness of the adhesion layer 2 on the sur-face 3 of the drum 4, with the drilling mud 1 viscosity from 10 to 100 centipoise, varied between 3 and 8 mm, and the solid particles of diameters between 0.8 and 4 mm where separated from the sur~ace of the adhesion layer 2. All the particles of the diameters short of the abovementioned ones remained within the adhesion layer.
The study has shown that the angular speed of the surface of the adhesion layer 2, contacting the ambient air, is signif-icantly lower (10 to 30 times) than the angular speed of the surface 3 of the drum 4. On account of this phenomenon, with the drum 4 rotated at speeds from 1000 and 2000 r.p.m., which are the optimum ones from the theoretical calculation made on 1153~63 the assumption that the adhesion layer 2 rigidl~ rotate~ with the drum 4, the particles of the solid phase of the minimum size of 0.07 mm cannot be separated to the required degree of purification.
If, however, the surface lager of the liguid is driven at the speed equalling the speed of rotation of the drum 4 by the action o~ the auxiliary drum 6, the theoretical calculation of the purification degree is completely sustained. When voltage .
of alternative polarity was fed to the drums 4 and 6 from the direct-c~rrent source 8, the fineness and degree of the purifi-cation were enhanced, owing to the reduced surface tension of the adhesion layer, with the minimum size of the solid phase particles removed from the adhesion layer being 20 microns.
It was found that a potential corresponding to the charge of the sludge particles, or rock cuttings had to be fed to the drum 4 while purifying drilling muds. Thus, if the sludge is represented by negatively charged particles of clay, a nega-tive potential is preferably fed to the drum 4, whereas with the sludge being represented by positively charged calcite particles, it is a positive potential that pre~erably has to be fed to the drum 4.
The studies also proved that to attain quality purificat-ion of drilling muds of viscosities from lO to lO0 cent.ipoise (to the minimum size of the removed particles egualling 20 mic-rons), it was necessary to rotate the drum 4 at speeds from , : :
1~$3963 1000 to 2000 ~.p.m. and to feed to the drum 4 the voltage of 10 to 20 V.
Thus, to purify the relatively clear drilling mud (30 to 40~0 solid phase) with the maximum size of the ~olid particles up to 200 - 300 microns, the diameter of the main drum was selected to be 420 to 500 mm, and the speed of its rotation was set at 1800 to 2000 r.p.m. The diameter of the auxiliary drum 6 was preferably 140 to 160 mm, and the speed of its ro-tation was set at 5000 to 6000 r.p.m. Under such conditions solid particles as small as I2 to 16 microns were separated from the adhesion layer.
It was further found that when the drilling mud with a high content of sludge and the size of the solid particles in excess of 1 mm had to be purified, the diameter of the main drum ~as preferably 100 to 120 mm, and the speed of its rota-tion was 1000 to 1200 r.p.m. The auxiliary drum diameter was preferab b from 30 to 40 mm, and the speed of its rotation was 3000 to 3600 r.p.m, Solid particles of a size from 40 to 50 microns were separated from the adhesion layer 2.
The economic effectiveness of the ~rein disclosed method of separating the solid phase in a drilling mud is made up of the reduced purification costs, owing to getting rid of a multis-tage purification system, of the prolonged life of the drilling mud and of faster drilling, due to the enhanced purification guality of the drilling mud.
Claims (7)
1. A method of separating the solid phase in a drilling mud, comprising forming an adhesion layer from the drilling mud on a curvilinear closed surface partly projected into the drilling mud and being rotated; then separating a portion of the formed adhesion layer onto another rotating curvilinear closed surface positioned so that this another surface contacts a portion of the adhesion layer; the respective linear speeds of the adhesion layer and of said another rotating closed cur-vilinear surface in the area of their contact being selected to be substantially equal.
2. A method of Claim 1, wherein a portion of said adhe-sion layer, enriched in coarser particles of the solid phase, is separated onto said another curvilinear closed surface.
3. A method of Claim 1, wherein a portion of the adhesion layer purified from the coarser particles of the solid phase is separated onto said another closed curvilinear surface.
4. A method of Claim 1, including varying the value of the surface tension of the adhesion layer in the process of se-parating the solid phase of the drilling mud.
5. A method of Claim 4, wherein the surface tension of the adhesion layer is varied by acting thereupon with a direct--current electric field.
6. A method of Claim 5, wherein the value of the surface tension of the adhesion layer is varied by altering the direc-tion of the electric current in accordance with the mineralogic composition of the solid phase of the drilling mud.
7. A method of claim 5 wherein the value of the surface tension of the adhesion layer is varied by varying the intensity of the electric field in accordance with the particle size content of the solid phase of the drilling mud.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000349984A CA1153963A (en) | 1980-04-16 | 1980-04-16 | Method of separation of solid phase in drilling mud |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000349984A CA1153963A (en) | 1980-04-16 | 1980-04-16 | Method of separation of solid phase in drilling mud |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1153963A true CA1153963A (en) | 1983-09-20 |
Family
ID=4116720
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000349984A Expired CA1153963A (en) | 1980-04-16 | 1980-04-16 | Method of separation of solid phase in drilling mud |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1153963A (en) |
-
1980
- 1980-04-16 CA CA000349984A patent/CA1153963A/en not_active Expired
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