CA1150667A - Method of separating solid phase in drilling mud and apparatus for performing this method - Google Patents
Method of separating solid phase in drilling mud and apparatus for performing this methodInfo
- Publication number
- CA1150667A CA1150667A CA000352090A CA352090A CA1150667A CA 1150667 A CA1150667 A CA 1150667A CA 000352090 A CA000352090 A CA 000352090A CA 352090 A CA352090 A CA 352090A CA 1150667 A CA1150667 A CA 1150667A
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- CA
- Canada
- Prior art keywords
- drilling mud
- adhesion layer
- purified
- solid phase
- drum
- Prior art date
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Abstract
ABSTRACT
The method of separating the solid phase in a drilling mud includes forming from the drilling mud an adhesion layer on a rotating curvilinear closed surface by partly introducing this surface into the drilling mud, and simultaneously treating the drilling mud and the adhesion layer formed therefrom in a direct-current electric field, to reduce the value of the surface tension in the adhesion layer, and regulating the angular speed of rotation of the curvilinear closed surface to attain the predetermined values of the centrifugal forces in the adhesion layer.
There is disclosed an apparatus for performing said method, comprising: receptacles adapted to receive the drilling mud to be purified and the purified drilling mud, respectively, and a driven drum accommodated above the receptacle for the drilling mud to be purified so that a portion of the periphe-ral surface thereof extends into the drilling mud, for the adhesion layer to be formed thereon; electrodes connectable to a direct-current source, adapted to produce an electric field in the drilling mud being purified and in the adhesion layer.
The method of separating the solid phase in a drilling mud includes forming from the drilling mud an adhesion layer on a rotating curvilinear closed surface by partly introducing this surface into the drilling mud, and simultaneously treating the drilling mud and the adhesion layer formed therefrom in a direct-current electric field, to reduce the value of the surface tension in the adhesion layer, and regulating the angular speed of rotation of the curvilinear closed surface to attain the predetermined values of the centrifugal forces in the adhesion layer.
There is disclosed an apparatus for performing said method, comprising: receptacles adapted to receive the drilling mud to be purified and the purified drilling mud, respectively, and a driven drum accommodated above the receptacle for the drilling mud to be purified so that a portion of the periphe-ral surface thereof extends into the drilling mud, for the adhesion layer to be formed thereon; electrodes connectable to a direct-current source, adapted to produce an electric field in the drilling mud being purified and in the adhesion layer.
Description
~L~5~6~i7 ME~OD OF SEPA~ TG SO~ID PHAS~ IN DRI~ G
~D A~D LPPARA~US FOR P~FORMING ~IS ~HOD
The present invention relates -to well-drilling technolo-gy, and more particularly it rela-tes to methods of separatlng the solid phase in a drilling mud and -to apparat-us adapted for performing such me-thods, ~ he herein disclosed method and apparatus can be utill-zed to utmost effectiveness in -the drilling o~ boreholes *or oil-producing wells~ natural gas producing wells a~d survey wells.
Howaver, the method and apparatus can be also used in general chemistr~, pharmaceu~ical and other industries where a solid phase has to be separated ~rom a suspension.
It is known that a drilling mud is a heteregene OU3 ~luid s~stem where colloid particles of the solid phase are always present. ~he presence of such particles in a drilling mud provides, ~ro~ the borehole-drilling point o~ view, a number o~ maaor rheological characteristics o~ the drilling mud. ~he latter is expected to retain these characteristics which are essential for promotion of the drilling process. However9 stable maintenance o~ the required properties of the drilling mud throughout the drilling c~cle presen~ts a complicated problem.
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~L15~667 The majori-ty of borehole-drilling jobs -takes place in clayey rock ancl soil. ~he clayey rock being~ drilled is partly disintegrated, and colloid particles thus produced become resident in the drilling mud.
Inadequately efficient purifica-tio~ of the drilling mud ~ollowing several pum~ing cycles in the course of the boreho-le-drilling operation significantly alters -the composi-tion of the drilling mud, which necessita-tes the adop-tion of various methods of enhancing the quality of the drilling mud, which me-thods, howeverj are more o~en than not ins~fficiently efIective. Thereforel quali-ty puri~ication o~ -the d~illing ~ud ~rom disintegrated rock particles, or sludge is of funda-mental importa~ce ~or the success of a borehole-drilling operation~
Poor quality of purification of -the drilling mud is a major cause o~ various emergencies and complications involving drilling mud losses t sticking or freezing of drill pipes an~
casings, caving-in of rock from the borehole walls~
The technical and economic ratings of a b~ehole-drilli~g operation are considerably dependent on -the quality of the drilling mud used and the degree of its purification from rock cuttings~
Quali-ty purification of the drilling mud enhc~nces the drilling rate and improves the oparating conditions of the :' ~
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~5~6367 drilling bits and other equipment. Aside rom the enhcmced drilling ra-te, quality purification of the drilling mud brings down the consump~ion of materials used for preserving the properties of the drilling mud, prolongs th~ service life thereof, helps avoiding complications and emergencies encoun-tered in a borehole-drilling operation.
~ hus, quality puri~ication of -the drilling mud ~rom rock cuttings is of major impoxta~ce in the borehole-drilling technology, essentially influencing as it does the ~echnical and economic ratings of -the drilling operation.
All the hitherto known apparatus -~or purification of ~he drilling mud provide ~or removing some o~ solid particles ~rom the circulating drilling mud a~ a certai~ rate and with certain quality. However, all of them are not free from a se-ries o~ disadvantages inherent in -the very principle o~ separa-tion on which they are based. hus, the minimum particle size o~ fines that can be separa-ted from -the drilling ~ud in vibra-ted screens is determined by the mesh size. I~ the meah ~ize is made ~lner ~o impr~v~ ~he purification quali-ty, the -through-put becomes affected, and -the was-te of the mud wi-th the sludge is stepped up.
When hydrocyclones are employed ~or -the puri~ica-tion, coarser particles are removed from the drilling mud, whereas particles with a lower density caused by dispersion o~ fi~er .. , , , ~ , ' ', . .
;67 rock cuttings in the drilling mud are not removable in hydrocyclones and like devices used for the purification.
There is known a method of regeneration of the stable clayey suspension of the drilling mud, according to which the sludge-carrying drilling mud emerging from the borehole is prediluted and processed to remove coarse particles In the thus dilutecl and purificed drilling mud there remain fine unchargecl particles of rock cuttings and negatively charged colloid clayey particles. Then the negatively charged clayey particles are separated from the drilling mud by deposition on a rotating anode, and sub-sequently removed therefrom with a scraper-like tool. The - negatively charged clayey particles being deposited entrainsome of the uncharged particles which also become deposited on the rotating anode~
The above-described known method purifies but - part of the drilling mud, while the substantially greater remaining part is fed into the borehole unpurified.
The puri~ication of but a part of the drilling mud, involving removing, first, coarser particles, and, I then, finer ones is complex, and hence costly.
It is an object of the present invention to create - a method of separation of the solid phase in a drilling mud, which should provide for purifying the entire volume of the drilling mud emerging from the borehole in a technologically simple manner.
It is another object of the present invention to reduce the drilling mud purification costs. I
It is still another object of the present inven- j tion to enhance the drilling rate by improving the quality of purification of the drilling mud. I
With these and other objects in view, there is hereby disclosed a method of separating the solid : - . , . ~ .:
phase in a drilling ~ud, including, in accordance with the present invention, forming an adhesion layer ~rom the dril-ling mud on a rota-ting curvilinear closed surface partlJ in-troduced into tke drilling mud, ~nd sirnulta~eousl-g trea-ting the drilling mud and the adhesion la~er formed therefrom in a~ electric field produced by a direct current, to reduce the surface tension value of -the adhesion layer, and regulating the angular speed of the rotatio~ of the curvilinear closed surface to attain the re~uired value o~ centrifugal a ~orces ithin the adhesion layer.
It is expedient to treat the drilling mud being purified with a low-voltage DC current-produced fi~ld.
This treatment enables to adjust the surface -tension in the adhesion layer, and~ conse~uently, to regulate the process o~ separation ~rom the adhesion layer of solid particles of a density hlgher than that of the drilling mud from which the adhesion layer is formed.
It ma~ be also expedient to treat -the adhesion layer in a high-voltage produced electric ~ield~
~ he action o~ a high-vol-tage electric field upon the adhesion layer reduces the latter's surface tension and results in electrically charged par-ticles of the solid phase being withrawn from this la~er.
I-t is expedient that -the electrosta-tic intensity of the . .
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~5~6~7 electric field produced by low voltage in the drilling mud should be varied in accordance with the value of the concen-tration o~ the solid phase in -the purieied drilling mud.
~ his kind o~ regulaGing enables to a-ttain an adequately high degree Oe puri~ication of drilling muds containing prac-tically any amount Oe rock cuttings.
It may also be expedient to var~ the direction of the high-voltage electric eield in the adhesion layer, depending on the mineralogical composition of the solid phase of the drilling mud. ra ~ his enables to sepate from the adhesion layer ei-ther the positively charged particles of -the solid phase, or the negatively charged ones, a-t will. ~hus 7 to separa-te barite particles charged positively, the adhesion la~er is acted upon by a high-voltage field of a negative polarity, without a low-voltage field being used. On the other hand, to separate ne-gatively charged colloidal particles, there is pre~`erably used a high-voltage field o~ a positive polari-ty~ with simul-taneously acting upon the drilling mud with a low-voltage ~ield.
It may also be advantageous -that the intensity O:e ~the high-vol-tage electric field should be varied depending on the size of the particles o~ the solid phase in -the drilling mud.
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The present invention further resides in an apparatus Por separating the solid phase in a drilling mud, compris-ing, in accordance with the invention, a receptacle adap-ted to contain the drilling mud to be purifi-ed ana a receptacle adapted to contain ~he pu~ified drilling ~ud, and a driven drum acnommodated above the receptacle with -the drilling mud to be purified so that a part of the cylindrical periphery thereof projects into the drilling mud to be puri~ d9 Por an adhesion layer to be formed thereon in the course o~ rotation of the drum, and electrodes connectable -to a direct-current voltage source, adapted to generate an electric field in -the drilling mud to be purified and in the adhesion la~er formed on the surface o~ the drum from the drilling mud to be purified.
While being of a rela-tivel~ simple struc-ture, the herein disclosed appara-tus enables to conduct puriPication of the entire volume o~ the drilling mud emerging from the borehole, and provides for a high degree o-f the purification.
In one embodiment of the inventionl one of the elect-rodes is mounted within the receptacle for the drilling mud to be puriPied, while another electrode is moun-ted within -the vessel for the purified drilling mud, both electrodes being connected to a low voltage direct-current source.
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~5~;7 I-t is further ad~isable that the apparatus should also include at least one electrode accommodated adjacen-t to the cylindrical surface of the drum,adapted to carry the adhesion layer, and at least one high voltage direct-current source having one output terminal thereof connected to the electrode accommodated in one of the two said receptacles ~or the dril-ling mud, and -the opposi-te-polarit~ other output terminAl there-of connected to the electrode accommoda-ted aajacent to the cylindrical surface of the drum, adapted to carr~ the adhesion layer, at a spacing in excess of -the high~volta~e break-through or punc-ture air gap.
~ he abovedescribed design enables to step up the rate and the degree of purification of the drilling mud.
I-t ma~ be expedient -that the electrode accommodated adaacent to the drum should be shaped as a portion of a hollow cylinder having its concave side facing the drum.
~ his shape of the electrode has been found to ensure that the electric ~ield exer-ts a uniform ac-tion upon tha ad-hesion layer.
It is ~urther expedient that the apparatus should incl-ude a responsive member or sensor adap-ted to produce a signal represen-tative of -the concentra-tion of the solid phase in -the puri~ied drilling mud, accommodated in ~the receptacle for collecting the purified ~rilling mud, and having i-ts output :: :
', ~151~66 _ 9 _ connected through a regulating device to the input of -the low-vol-tage c~irec-t-curreIrt SouI ce .
It may be also practicable that ~he responsive member adapted to produce a signal represen-tative o~ -the concentration of the solid phase in the purified drilling mud should have i~s outpu-t connected to the input OI the high-voltage direc-t-current source~
~ he provision of said repsonsive member or sensor provides ~or automatic regulating of the value of the sur-face tension o~ the adhesive layer, and, hence, ~or maintaining the pre-determined content of the solid phase particles in the purifi~
ed drilling mud.
Thus, the herein discloseà method of separating the s~lid phase in a drilling mud and the apparatus capable o~
performing this method provide for attaining a high degree o~ puri~ication o~ the entire volume of the drilling mud, for regulating the degree o~ withdxawal of ~he ~o~~id phase wit~in a broad range, and ~r having selectivit~ o~ the withdrawal of ~olid particles, depending on -the mineralogical composition o, the solid phase. The substantial technical advantages to be gained by the herein disclosed me-thod are at-tained in a simple technology involving economic operations~ ~he apparatu~ capab-le of performing the disclosed method is relatively simple and compact, its ~-iving arra~gement being uncomplicated~ ~he uti- :
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l:~S06~7 lization of ~he ~resent inventiorL offers subs-tarl-tial economy over the hitherto known practice of employing appara-tus of the prior art for purifiyin~ the drilling mud used in a bore-hole drilling operation.
~ iven hereinbelow is a description of an embodiment of the presen-t invention~ with reference being made to the accompanying drawings, wherein:
Fig.l schematically illustrates in a cross-sectional view P~n apparatus for separating the solid phase of a drill-ing mud, embodying the invention, wi-th the drive system o~
the drum not shou~;
Fig.2 shows a plan view of the apparatus illu~trated ln Fig.l, with the high-voltage electrodes and sludge rec~p-tacles removed for clari-ty sake.
An unpurified drilling mud receptacle 1 (Fig.l) has the unpurified drilling mud 2 being supplied thereinto. ~he rota--table curvilinear closed surface is in the form o~ a drum 3~
~he drum 3 has its periphery partly submerged into the dril-ling mud 2, to form thereon an adhesion layer 4 upon rotation of the drum 3. ~he unpuri~ied drilling mud 2 and -the adhe-sion layer 4 evolved therefrom are treated in an electric ~ield crea-ted by a direct current, to reduce the value of -the surface ten3ion of the drllling mud 2 ln the adhesion layer 4.
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~L~l5~667 ~he angular speed of the drum 3 is regulated -to create -the prede-termined level o~ the cen-tril`ugal forces within the adhesion layer 4, depending on the mineralogical co~position of the drilling mud 2 being purified. ~hus, the centrifugal forces de-veloping in the adhesion layer 4 upon rotation of the drum 3 provide for separation o~ the solid phase particles from this ayer, depending on the mineralo~ical co~position of the dril-ling mud 2. ~he drilling mud 2 being purified is treated in a lo~w-vol~age electric field of which the intensity is varied, depending on the value of the concentration of the solid phase in the purified drilling mud. ~he adhesion layer 4 produced from the drilling mud 2 being purified is -treated in a high-voltage electric ~ield. ~he direction or sense o~ the high-voltage electric ~ield can be varied, depending o~ the mineralogi-cal composition of -the solid phase of -the drilling mud 2 being pu~i~ied, while the value o~ the intensity o~ -this elec-tr1c field is varied, depending on the size o~ the solid phase particlas in the drilling mud 2 being puri~ied.
~ he essence o~ -the method in accorda~ce with the preseNt invention will be described hereinbelow in greater detail, in connection with the description o~ the apparatus capable of per~orming this ~ethod, to be described bo-th in a statlc state and in operation.
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~5V667 ~ he apparatus for separa~ing the ~olid phase in a dril-li~g ~lud comprises a receptacle 1 (Figs l and 2) adapted to receive and con-tain therein a dr:illing mud -to be purified, partly accommodating therein a drum 3 operatively connected to a drive 5 (~ig.2) through an r.p,m. regula-tor 6. A scraper 7 is provided ~or stripping the layer of the puri~ied drilling mud 8 o~ -the periphery of the drum 3. A receptacle 9 is moun-ted adjacent to the receptaGle 1, adapted to receive and con-tain therein the puri~ied drilling mud 8. An electrode 10 is mounted within the receptacle 1, and an elec-trode 11 is moun-ted within the receptacle 9. The electrodes 10 and 11 are con-nected to a lo~-vol-tage direct-current source 12, with the electrode lQ being connected to the negative terminal o~ the source 12, and the ele~,trode 11 being connected to the posi-tive terminal thereo~.
The receptacles 1 and 9 are made o~ a dielectric ma-teri-al.
To act upon the adhesion la~er 4 with a high-voltage field, the apparatus includes high-vol-tage direct-curren-t sources 13 and 14, and high-voltage electrodes 15 and 16 mounted above the drum 3 adjacent thereto. ~he negative -ter-minal of the high-voltage DC source 13 is connected to the hi~h-voltage electrode 15, and its positi~e ter~inal is con-nected to the electrode 10.
, ~S~667 The positve terminal of the high-vol-tage directcurrent source 14 is connected to the high-voltage elec-trod& 16; and its negative ter~inal is connectea to the electrode 11.
~ he high-voltage ~ectrodes 15 and 16 are spaced f.rom the drum 3 by a dis-tance in excess o~ the breakthrough or puncture voltage gap, to avoid the high voltage o~ the sources 13 and 14 breaking through this gap.
The high-voltage electrodes 15 and 16 are shaped as portions of a hollow cylinder and have their concave sides facing the drum 3. This design of the high-voltage electro-des 15 and 16 provides for producing a substantially unifor~
high-voltage electric field acting upon -the a~esion layer 4.
~ o collec-t the sludge separated ~rom -the drilling mud 2, the apparatus includes sludge receptacles 17 and 18 mounted to underlie the high-voltage electrodes 15 and 16, respective-ly.
The receptacle 9 accommodates a sensor 19 adapted to produce a signal representative of the concentration of the solid phase in the purified drilling mud 8. The sensor 19 has its output connected via a regulating device 20 to the inputs of the sources 14 and 12 of high~voltage and low-vol~
~ tage, respectively.
:~ The apparatus operates, as follows.
The drill:;ng mud 2 to be purified i~ supplied into the i. , ,, :
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~ 14 -receptacle l. 'rhe drum 3 is ~o-tated by the drive 5 through the r.p.m~ regulator 59 and forms on the peripheral surface thereof an adhesion layer 4.
The adhesion layer 4 col~tains therein all th~ fractions of -the solid phase con-tained in t;he drilli~g mud 2, ~nder the actio~ of centrifugal forces and surface tension, -the solid particles become redistributed in the adhesion la-~er 4 in accordance with their size or volume and mass. The heavier and larger particles of -the solid phase migra-te -toward the external sur~`ace of the adhesion layer 4, whereas ~he finer - part~cles, and, particularly, the colloid or colloid-size o~es become concentrated at the internal surface Gf the adhe-sion layer 4, next to the peripheral cylindrical surface of the drum 3. As the drum 3 rotates, depending on -the speed of the adhesion layer 4~ the larger or coarser particles of sludge leave the surface of the adhesion layer 4, while the remaining layer of the fluid containing the colloid clayey particles is directed into the receptacle 9 for further use. A solid phase particle in the adhesion layer 4 has acting upon it, on the one hand, centrifugal ~orces:
F = m V , (1) where 7'm7' is the ~ass of a particle; "R" is the radius of its rotation, and "V" is the linear velocity of the rotation of the peripheral surface of the drum 3, , :
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- . , _ 15 _ and on -the other hand, it has acting upon it its weight 9 the viscous ~riction forces and forces Fl o~ -the sur~ace tension of the adhesion layer 4-, ~ 1 = 2~r ~, (2) where "r" is the radius of the particle, and "~" is the sur-~ace ~riction ~actor o~ the drilling mud 2.
~he evalua-tion o~ the relative significance of the ~orces taking part in -the distribution of the solid particles through the adhesion layer ca~ be done by applying the Foude cr~terion showing the ratio o~ the centrifugal ~orces -to gravity ~orces in a ~iven unit.
Fr = R (3) g ~here "~" is the angular speed of rotation o~ the drum 3;
"R" is the radius of rotation o~ the particle;
"g" is the gravity aGceleration.
~ he maximum and minimum values of ~roude numbers for real~ e structures are within 20 to 2000.
It Gan be see~ from the abovesaid that wh~en the ~orces acting upon solid particles in the adhesion la~er ~ are calc-ulated5 it is unnecessar~ to make provisions ~or their weight, . since the centr:i~ugal or inertia ~orces are 20 to 2000 times greater. Since th2 ~ric-tion ~orce between the sur~ace o~ the solid phase part-icles and the ~luid en-training -them ~or rotat-.
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ion 1~ diracted ta~entiall,y kc th~ ~urf~cs of th~ drum 3 and perpendicularly to tbe radius th~reD~, khe peculiariti~
D e tbe radi~l m~tio~ of t,he par~icle~ e. ~he ba~lc lo~ ~ the proce~ o~ paration D~ the pba~e~ and fraction~. (i.e. of t~e p~rificat~on proce3~3-may be G~n8 . .
dered wit~out prDeisio~s for t~e ~i~cou~ ~rie~ion Iorce~.
Tbu3, b,~ ~s~un~g the equalit~ of the a4ntri~u~al ... . . . . . ..
rces "1?'l a~d th0 ~urface te~slD~ *orc~ tb~re can be ~ormul~t~d the CD~ditiD~I D:e equ:ilib~i um oi par~lale~
in the adbesion la,ye~ 4 o~ t~e c,yli~drical p~ripheral surface ~f the r~-Abing dr~lm 3:
~d 3 ( JJ _ p ) cl,2f~ - r~, (4) or el~s, relabive t~ the diameber of ~ par~icle (~h~c~
latter i~ conditio~ll,y tske~ b~ be ~pherlcal~"
d = \~¦f~ ;" 2~ -~heres "d'~ he dismeter c~ a p~rb$cla (d = 2r);
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",P1" a~d "J~2 " ~re, re~pectiv~l,y9 the den~ity of the sol~d phass a~d ~f t~e liSIuid?
"~ s r~diu~ of rotatio~ ~ bhe part;icle~
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tha ~ac~ ~rlcb~on ~actor ~ the liqui~
tbe a~heslo~ er 4.
I1; ca~ be ~een ~rom expression~ (4~ and (5) b~ali tb~
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~15~6~7 -- 17 _ movement o~ a particle of a diameter "d" within the adhesion layer 4 a~d its expulsion from -this layer depend on -the den_ sity of -the dispersio~ medium, the radius 'IR" of -the circular path of ro-tation of the paxticle, the speed of its ro-tation and the value o~ the sur~ace tension o~ the adhesion layer 4.
~he radius o~ the circular path of rotation of the particle is de~ined by the diameter of the drum 3.
Increasing the diameter of the drulll 3 is limi~ed by bhe ~tructu~al consldera~ions and the Illanu~c-~uring ~omp7ex~t~.
~here~or~ bhe major par~me~r~ of the process o~ ~parR~io~
o~ tne solid phase in t~ drilling mud 2 on the rotating cy-lindrical surface of the drum 3 are the angular speed of its rotation and the value o~ the surface -tension o~ the adhesion la~er 4~
By varying the r.p.m. of the drum 3 and the value of the surface tension of the adhesion layer 4, it is possible to regulate within a broad range the process of separation o~ the solid phase in the drilling mud 2, so as to remove the surplus solid phase and -to retain the fine clayey particles which are the major colloid componen-t of a cla~ey drilling ~ud~ :
To remove the weighting material from -the drilling mud ~ -by its cen-trifugal separation, the solid rock cuttings are disin-tegrated, prior to the separation, -to -the particle size ~-of the weighting material. In this case the weighting material .
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6~7 ~ 18 -par-ticles of the speci~ic mass of 4 2 g/cm3 are separated f`rom the surface of the adhesion layer under an~ given condi-tions generally faster than the particles of sludge,which have -the same size but a lower specific mass (2.6 g/cm3). ~he purified ad-hesion layer 4 of the drilling ~ud 2 is scraped off b~ the scraper 7 ~nd directed in-to the receptacle 9 ~ o reduce the ~alue of the surface -tension and -to regu-late this value, low-voltage direct electric curren-t is made to flow through the drilling mud and the adhesion layer 4 from the direct-current low-volta~e source 12 via the ~ollowing circuit: negative terminal of the direct~current source 12 -electrode 10 - drilling mud 2 being purified - adhesion la-yer 4 - purified drilling mud 8 - electrode 11 - positive -ter-minal of the low-voltage direct-current source 12. The electro-de 10 thus acting as the cathode9 the electrolysis of salts contained in the purified drilling mud 2 within the receptacle 1 results in -the increasing pH value of the medium. As it is nown from drilling practice, this increase of the pE value reduces the surface tension. ~herefore, by varying the value o~ the low-~ol~age electric current flowing through the drillin~
mud, the value of the surface tension can be regulated.
~ nder the action of the flowing elec-tric current, charged particles are produced wi-thin the adhesion layer. ~o amplify -the inlDluence of the charge of the charged particle~ upon the `: :
~L5~7 sur~ace tension o~ the drilling mud in the adhesion la~er 4~
and to enhance the conditions o~ separation of -the solid phase particles of a certain mineralogical composi-tion in -the aahesion layer 4 ~ there are produced in the latter -the areas o~ high-voltage electric fields. ~he portion o~ the adhesion layer which is the area opposing the negatively charged electrode 15 is always charged positlvely ~rom the high-voltage source 13 along the circuit: positive terminal o~ the high-voltage direct-current source 13 - electrode 10 - drilling mud 2 to be purified - adhesion layer 4, ~he positive charge o~ the particles moving toward the e~ternal surface o~ the adhesion layer 4 provides for separation in this area~ to the greater degree, of neutral and positively charged particles (io e.
mainly OL the weighting material).
~ he other piortion of the adhesion layer 4, i,e. the area facing the positvely charged electrode 16 ls al~a~s charg~d negatively ~rol~ tne high-volta~e ~ource 14 via the eircuit:
nega~ve ~erminai of ~he ~lgh-~o~tage ~irec~-current source 14 - electroae 17 - puriYied ari~ n~ mud ~ - adhesion layer 4.
In this zone negatively charged particles o~ clay move toward the surface of the adhesion layer 4.
Under the action of the centri~ugal forces, the reduced surface tension and the high-voltage electric field, the charged par-ticles contained in the adhesion layer are expelled .
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;67 from this layer 4 into the respective sludge receptacles 17 and 18 arranged to underlie the respective electrodes 15 and 16. Some of the chargecl particles as far as the respective high-voltage electrodes 15 and 16 where they lose their charge and flow down the planes of the high-voltage electrodes 15 and 16 into the respective sludge collectors 17 and 18.
Therefore, the herein disclosed apparatus is operable to separate the drilling mud in a single process into three parts, Within the first area or zone, it is the weighting material that is predominantly separated.
Clayey rock particles are removed in the second area.
The third part is the drilling mud purified from the extra solid phase.
The sensor 19 of concentration of the solid phase, accommodated in the flow of the purified drilling mud 8 is used to maintain the optimum duty of the purifi-cation of the drilling mud 2, An example of implementation of the disclosed method can be provided by data obtained by a series of tests aimed at determining the optimum parameters of the operation of purifying the drilling mud 2. There were tested various drums 3 of diameters ranging from 100 to 500 mm, rotatable from 10 to 10,000 r.p.m. It has been found that with the drum 3 rotated at speeds from 1000 to 2000 r.p.m. the thickness of the formed adhesion layer 4 of the drilling mud of a viscosity from 10 :
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to lQO cen-tipoise is from 15 to 30 mm. Under the action of the low and high voltage supplied by the sources 12, 13, 14 o~
direct current there has been a-ttained satis~ac-tory puri~i-cation oL the drilling mud from sludge and removal o-f the weighting material.
~ hus, the herein disclosed method of separa-ting the solid phase in a drilling mud and the apparatus performing this method offer considerable technical advantages over purifying devices currently in use in the drillin~ operation.
By regulating the speed of rotation of the drum 39 by ~arying the values of the high and low direct-current voltage supplied, there is attained a high degree of the purification o~ the drilling mud at relatively low investment a~d operat-ing costs. ~he absence o~ complicated driving arrangements facilitates reliable per~ormance of the apparatus in an au-to-matic mode.
~ he economic e~iciency o~ implemen-ta-tion o~ -the present inv~n-tion is defined by the reduced cost o~ purif~ing -the dril-ling mud, reduced consumption o~ chemical agents and higher mech~lical drilling rates, owing to the enhanced quality of the purifica-tion of -the drilling mu.d.
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~D A~D LPPARA~US FOR P~FORMING ~IS ~HOD
The present invention relates -to well-drilling technolo-gy, and more particularly it rela-tes to methods of separatlng the solid phase in a drilling mud and -to apparat-us adapted for performing such me-thods, ~ he herein disclosed method and apparatus can be utill-zed to utmost effectiveness in -the drilling o~ boreholes *or oil-producing wells~ natural gas producing wells a~d survey wells.
Howaver, the method and apparatus can be also used in general chemistr~, pharmaceu~ical and other industries where a solid phase has to be separated ~rom a suspension.
It is known that a drilling mud is a heteregene OU3 ~luid s~stem where colloid particles of the solid phase are always present. ~he presence of such particles in a drilling mud provides, ~ro~ the borehole-drilling point o~ view, a number o~ maaor rheological characteristics o~ the drilling mud. ~he latter is expected to retain these characteristics which are essential for promotion of the drilling process. However9 stable maintenance o~ the required properties of the drilling mud throughout the drilling c~cle presen~ts a complicated problem.
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~L15~667 The majori-ty of borehole-drilling jobs -takes place in clayey rock ancl soil. ~he clayey rock being~ drilled is partly disintegrated, and colloid particles thus produced become resident in the drilling mud.
Inadequately efficient purifica-tio~ of the drilling mud ~ollowing several pum~ing cycles in the course of the boreho-le-drilling operation significantly alters -the composi-tion of the drilling mud, which necessita-tes the adop-tion of various methods of enhancing the quality of the drilling mud, which me-thods, howeverj are more o~en than not ins~fficiently efIective. Thereforel quali-ty puri~ication o~ -the d~illing ~ud ~rom disintegrated rock particles, or sludge is of funda-mental importa~ce ~or the success of a borehole-drilling operation~
Poor quality of purification of -the drilling mud is a major cause o~ various emergencies and complications involving drilling mud losses t sticking or freezing of drill pipes an~
casings, caving-in of rock from the borehole walls~
The technical and economic ratings of a b~ehole-drilli~g operation are considerably dependent on -the quality of the drilling mud used and the degree of its purification from rock cuttings~
Quali-ty purification of the drilling mud enhc~nces the drilling rate and improves the oparating conditions of the :' ~
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~5~6367 drilling bits and other equipment. Aside rom the enhcmced drilling ra-te, quality purification of the drilling mud brings down the consump~ion of materials used for preserving the properties of the drilling mud, prolongs th~ service life thereof, helps avoiding complications and emergencies encoun-tered in a borehole-drilling operation.
~ hus, quality puri~ication of -the drilling mud ~rom rock cuttings is of major impoxta~ce in the borehole-drilling technology, essentially influencing as it does the ~echnical and economic ratings of -the drilling operation.
All the hitherto known apparatus -~or purification of ~he drilling mud provide ~or removing some o~ solid particles ~rom the circulating drilling mud a~ a certai~ rate and with certain quality. However, all of them are not free from a se-ries o~ disadvantages inherent in -the very principle o~ separa-tion on which they are based. hus, the minimum particle size o~ fines that can be separa-ted from -the drilling ~ud in vibra-ted screens is determined by the mesh size. I~ the meah ~ize is made ~lner ~o impr~v~ ~he purification quali-ty, the -through-put becomes affected, and -the was-te of the mud wi-th the sludge is stepped up.
When hydrocyclones are employed ~or -the puri~ica-tion, coarser particles are removed from the drilling mud, whereas particles with a lower density caused by dispersion o~ fi~er .. , , , ~ , ' ', . .
;67 rock cuttings in the drilling mud are not removable in hydrocyclones and like devices used for the purification.
There is known a method of regeneration of the stable clayey suspension of the drilling mud, according to which the sludge-carrying drilling mud emerging from the borehole is prediluted and processed to remove coarse particles In the thus dilutecl and purificed drilling mud there remain fine unchargecl particles of rock cuttings and negatively charged colloid clayey particles. Then the negatively charged clayey particles are separated from the drilling mud by deposition on a rotating anode, and sub-sequently removed therefrom with a scraper-like tool. The - negatively charged clayey particles being deposited entrainsome of the uncharged particles which also become deposited on the rotating anode~
The above-described known method purifies but - part of the drilling mud, while the substantially greater remaining part is fed into the borehole unpurified.
The puri~ication of but a part of the drilling mud, involving removing, first, coarser particles, and, I then, finer ones is complex, and hence costly.
It is an object of the present invention to create - a method of separation of the solid phase in a drilling mud, which should provide for purifying the entire volume of the drilling mud emerging from the borehole in a technologically simple manner.
It is another object of the present invention to reduce the drilling mud purification costs. I
It is still another object of the present inven- j tion to enhance the drilling rate by improving the quality of purification of the drilling mud. I
With these and other objects in view, there is hereby disclosed a method of separating the solid : - . , . ~ .:
phase in a drilling ~ud, including, in accordance with the present invention, forming an adhesion layer ~rom the dril-ling mud on a rota-ting curvilinear closed surface partlJ in-troduced into tke drilling mud, ~nd sirnulta~eousl-g trea-ting the drilling mud and the adhesion la~er formed therefrom in a~ electric field produced by a direct current, to reduce the surface tension value of -the adhesion layer, and regulating the angular speed of the rotatio~ of the curvilinear closed surface to attain the re~uired value o~ centrifugal a ~orces ithin the adhesion layer.
It is expedient to treat the drilling mud being purified with a low-voltage DC current-produced fi~ld.
This treatment enables to adjust the surface -tension in the adhesion layer, and~ conse~uently, to regulate the process o~ separation ~rom the adhesion layer of solid particles of a density hlgher than that of the drilling mud from which the adhesion layer is formed.
It ma~ be also expedient to treat -the adhesion layer in a high-voltage produced electric ~ield~
~ he action o~ a high-vol-tage electric field upon the adhesion layer reduces the latter's surface tension and results in electrically charged par-ticles of the solid phase being withrawn from this la~er.
I-t is expedient that -the electrosta-tic intensity of the . .
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~5~6~7 electric field produced by low voltage in the drilling mud should be varied in accordance with the value of the concen-tration o~ the solid phase in -the purieied drilling mud.
~ his kind o~ regulaGing enables to a-ttain an adequately high degree Oe puri~ication of drilling muds containing prac-tically any amount Oe rock cuttings.
It may also be expedient to var~ the direction of the high-voltage electric eield in the adhesion layer, depending on the mineralogical composition of the solid phase of the drilling mud. ra ~ his enables to sepate from the adhesion layer ei-ther the positively charged particles of -the solid phase, or the negatively charged ones, a-t will. ~hus 7 to separa-te barite particles charged positively, the adhesion la~er is acted upon by a high-voltage field of a negative polarity, without a low-voltage field being used. On the other hand, to separate ne-gatively charged colloidal particles, there is pre~`erably used a high-voltage field o~ a positive polari-ty~ with simul-taneously acting upon the drilling mud with a low-voltage ~ield.
It may also be advantageous -that the intensity O:e ~the high-vol-tage electric field should be varied depending on the size of the particles o~ the solid phase in -the drilling mud.
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- : . . ~ : . - , ~IL5~6~7 '~his enables to control the volume of -the withdrawal o~ soli~ phase particles from -the drilling ~ud~
The present invention further resides in an apparatus Por separating the solid phase in a drilling mud, compris-ing, in accordance with the invention, a receptacle adap-ted to contain the drilling mud to be purifi-ed ana a receptacle adapted to contain ~he pu~ified drilling ~ud, and a driven drum acnommodated above the receptacle with -the drilling mud to be purified so that a part of the cylindrical periphery thereof projects into the drilling mud to be puri~ d9 Por an adhesion layer to be formed thereon in the course o~ rotation of the drum, and electrodes connectable -to a direct-current voltage source, adapted to generate an electric field in -the drilling mud to be purified and in the adhesion la~er formed on the surface o~ the drum from the drilling mud to be purified.
While being of a rela-tivel~ simple struc-ture, the herein disclosed appara-tus enables to conduct puriPication of the entire volume o~ the drilling mud emerging from the borehole, and provides for a high degree o-f the purification.
In one embodiment of the inventionl one of the elect-rodes is mounted within the receptacle for the drilling mud to be puriPied, while another electrode is moun-ted within -the vessel for the purified drilling mud, both electrodes being connected to a low voltage direct-current source.
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~5~;7 I-t is further ad~isable that the apparatus should also include at least one electrode accommodated adjacen-t to the cylindrical surface of the drum,adapted to carry the adhesion layer, and at least one high voltage direct-current source having one output terminal thereof connected to the electrode accommodated in one of the two said receptacles ~or the dril-ling mud, and -the opposi-te-polarit~ other output terminAl there-of connected to the electrode accommoda-ted aajacent to the cylindrical surface of the drum, adapted to carr~ the adhesion layer, at a spacing in excess of -the high~volta~e break-through or punc-ture air gap.
~ he abovedescribed design enables to step up the rate and the degree of purification of the drilling mud.
I-t ma~ be expedient -that the electrode accommodated adaacent to the drum should be shaped as a portion of a hollow cylinder having its concave side facing the drum.
~ his shape of the electrode has been found to ensure that the electric ~ield exer-ts a uniform ac-tion upon tha ad-hesion layer.
It is ~urther expedient that the apparatus should incl-ude a responsive member or sensor adap-ted to produce a signal represen-tative of -the concentra-tion of the solid phase in -the puri~ied drilling mud, accommodated in ~the receptacle for collecting the purified ~rilling mud, and having i-ts output :: :
', ~151~66 _ 9 _ connected through a regulating device to the input of -the low-vol-tage c~irec-t-curreIrt SouI ce .
It may be also practicable that ~he responsive member adapted to produce a signal represen-tative o~ -the concentration of the solid phase in the purified drilling mud should have i~s outpu-t connected to the input OI the high-voltage direc-t-current source~
~ he provision of said repsonsive member or sensor provides ~or automatic regulating of the value of the sur-face tension o~ the adhesive layer, and, hence, ~or maintaining the pre-determined content of the solid phase particles in the purifi~
ed drilling mud.
Thus, the herein discloseà method of separating the s~lid phase in a drilling mud and the apparatus capable o~
performing this method provide for attaining a high degree o~ puri~ication o~ the entire volume of the drilling mud, for regulating the degree o~ withdxawal of ~he ~o~~id phase wit~in a broad range, and ~r having selectivit~ o~ the withdrawal of ~olid particles, depending on -the mineralogical composition o, the solid phase. The substantial technical advantages to be gained by the herein disclosed me-thod are at-tained in a simple technology involving economic operations~ ~he apparatu~ capab-le of performing the disclosed method is relatively simple and compact, its ~-iving arra~gement being uncomplicated~ ~he uti- :
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l:~S06~7 lization of ~he ~resent inventiorL offers subs-tarl-tial economy over the hitherto known practice of employing appara-tus of the prior art for purifiyin~ the drilling mud used in a bore-hole drilling operation.
~ iven hereinbelow is a description of an embodiment of the presen-t invention~ with reference being made to the accompanying drawings, wherein:
Fig.l schematically illustrates in a cross-sectional view P~n apparatus for separating the solid phase of a drill-ing mud, embodying the invention, wi-th the drive system o~
the drum not shou~;
Fig.2 shows a plan view of the apparatus illu~trated ln Fig.l, with the high-voltage electrodes and sludge rec~p-tacles removed for clari-ty sake.
An unpurified drilling mud receptacle 1 (Fig.l) has the unpurified drilling mud 2 being supplied thereinto. ~he rota--table curvilinear closed surface is in the form o~ a drum 3~
~he drum 3 has its periphery partly submerged into the dril-ling mud 2, to form thereon an adhesion layer 4 upon rotation of the drum 3. ~he unpuri~ied drilling mud 2 and -the adhe-sion layer 4 evolved therefrom are treated in an electric ~ield crea-ted by a direct current, to reduce the value of -the surface ten3ion of the drllling mud 2 ln the adhesion layer 4.
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~L~l5~667 ~he angular speed of the drum 3 is regulated -to create -the prede-termined level o~ the cen-tril`ugal forces within the adhesion layer 4, depending on the mineralogical co~position of the drilling mud 2 being purified. ~hus, the centrifugal forces de-veloping in the adhesion layer 4 upon rotation of the drum 3 provide for separation o~ the solid phase particles from this ayer, depending on the mineralo~ical co~position of the dril-ling mud 2. ~he drilling mud 2 being purified is treated in a lo~w-vol~age electric field of which the intensity is varied, depending on the value of the concentration of the solid phase in the purified drilling mud. ~he adhesion layer 4 produced from the drilling mud 2 being purified is -treated in a high-voltage electric ~ield. ~he direction or sense o~ the high-voltage electric ~ield can be varied, depending o~ the mineralogi-cal composition of -the solid phase of -the drilling mud 2 being pu~i~ied, while the value o~ the intensity o~ -this elec-tr1c field is varied, depending on the size o~ the solid phase particlas in the drilling mud 2 being puri~ied.
~ he essence o~ -the method in accorda~ce with the preseNt invention will be described hereinbelow in greater detail, in connection with the description o~ the apparatus capable of per~orming this ~ethod, to be described bo-th in a statlc state and in operation.
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~5V667 ~ he apparatus for separa~ing the ~olid phase in a dril-li~g ~lud comprises a receptacle 1 (Figs l and 2) adapted to receive and con-tain therein a dr:illing mud -to be purified, partly accommodating therein a drum 3 operatively connected to a drive 5 (~ig.2) through an r.p,m. regula-tor 6. A scraper 7 is provided ~or stripping the layer of the puri~ied drilling mud 8 o~ -the periphery of the drum 3. A receptacle 9 is moun-ted adjacent to the receptaGle 1, adapted to receive and con-tain therein the puri~ied drilling mud 8. An electrode 10 is mounted within the receptacle 1, and an elec-trode 11 is moun-ted within the receptacle 9. The electrodes 10 and 11 are con-nected to a lo~-vol-tage direct-current source 12, with the electrode lQ being connected to the negative terminal o~ the source 12, and the ele~,trode 11 being connected to the posi-tive terminal thereo~.
The receptacles 1 and 9 are made o~ a dielectric ma-teri-al.
To act upon the adhesion la~er 4 with a high-voltage field, the apparatus includes high-vol-tage direct-curren-t sources 13 and 14, and high-voltage electrodes 15 and 16 mounted above the drum 3 adjacent thereto. ~he negative -ter-minal of the high-voltage DC source 13 is connected to the hi~h-voltage electrode 15, and its positi~e ter~inal is con-nected to the electrode 10.
, ~S~667 The positve terminal of the high-vol-tage directcurrent source 14 is connected to the high-voltage elec-trod& 16; and its negative ter~inal is connectea to the electrode 11.
~ he high-voltage ~ectrodes 15 and 16 are spaced f.rom the drum 3 by a dis-tance in excess o~ the breakthrough or puncture voltage gap, to avoid the high voltage o~ the sources 13 and 14 breaking through this gap.
The high-voltage electrodes 15 and 16 are shaped as portions of a hollow cylinder and have their concave sides facing the drum 3. This design of the high-voltage electro-des 15 and 16 provides for producing a substantially unifor~
high-voltage electric field acting upon -the a~esion layer 4.
~ o collec-t the sludge separated ~rom -the drilling mud 2, the apparatus includes sludge receptacles 17 and 18 mounted to underlie the high-voltage electrodes 15 and 16, respective-ly.
The receptacle 9 accommodates a sensor 19 adapted to produce a signal representative of the concentration of the solid phase in the purified drilling mud 8. The sensor 19 has its output connected via a regulating device 20 to the inputs of the sources 14 and 12 of high~voltage and low-vol~
~ tage, respectively.
:~ The apparatus operates, as follows.
The drill:;ng mud 2 to be purified i~ supplied into the i. , ,, :
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~ 14 -receptacle l. 'rhe drum 3 is ~o-tated by the drive 5 through the r.p.m~ regulator 59 and forms on the peripheral surface thereof an adhesion layer 4.
The adhesion layer 4 col~tains therein all th~ fractions of -the solid phase con-tained in t;he drilli~g mud 2, ~nder the actio~ of centrifugal forces and surface tension, -the solid particles become redistributed in the adhesion la-~er 4 in accordance with their size or volume and mass. The heavier and larger particles of -the solid phase migra-te -toward the external sur~`ace of the adhesion layer 4, whereas ~he finer - part~cles, and, particularly, the colloid or colloid-size o~es become concentrated at the internal surface Gf the adhe-sion layer 4, next to the peripheral cylindrical surface of the drum 3. As the drum 3 rotates, depending on -the speed of the adhesion layer 4~ the larger or coarser particles of sludge leave the surface of the adhesion layer 4, while the remaining layer of the fluid containing the colloid clayey particles is directed into the receptacle 9 for further use. A solid phase particle in the adhesion layer 4 has acting upon it, on the one hand, centrifugal ~orces:
F = m V , (1) where 7'm7' is the ~ass of a particle; "R" is the radius of its rotation, and "V" is the linear velocity of the rotation of the peripheral surface of the drum 3, , :
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- . , _ 15 _ and on -the other hand, it has acting upon it its weight 9 the viscous ~riction forces and forces Fl o~ -the sur~ace tension of the adhesion layer 4-, ~ 1 = 2~r ~, (2) where "r" is the radius of the particle, and "~" is the sur-~ace ~riction ~actor o~ the drilling mud 2.
~he evalua-tion o~ the relative significance of the ~orces taking part in -the distribution of the solid particles through the adhesion layer ca~ be done by applying the Foude cr~terion showing the ratio o~ the centrifugal ~orces -to gravity ~orces in a ~iven unit.
Fr = R (3) g ~here "~" is the angular speed of rotation o~ the drum 3;
"R" is the radius of rotation o~ the particle;
"g" is the gravity aGceleration.
~ he maximum and minimum values of ~roude numbers for real~ e structures are within 20 to 2000.
It Gan be see~ from the abovesaid that wh~en the ~orces acting upon solid particles in the adhesion la~er ~ are calc-ulated5 it is unnecessar~ to make provisions ~or their weight, . since the centr:i~ugal or inertia ~orces are 20 to 2000 times greater. Since th2 ~ric-tion ~orce between the sur~ace o~ the solid phase part-icles and the ~luid en-training -them ~or rotat-.
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ion 1~ diracted ta~entiall,y kc th~ ~urf~cs of th~ drum 3 and perpendicularly to tbe radius th~reD~, khe peculiariti~
D e tbe radi~l m~tio~ of t,he par~icle~ e. ~he ba~lc lo~ ~ the proce~ o~ paration D~ the pba~e~ and fraction~. (i.e. of t~e p~rificat~on proce3~3-may be G~n8 . .
dered wit~out prDeisio~s for t~e ~i~cou~ ~rie~ion Iorce~.
Tbu3, b,~ ~s~un~g the equalit~ of the a4ntri~u~al ... . . . . . ..
rces "1?'l a~d th0 ~urface te~slD~ *orc~ tb~re can be ~ormul~t~d the CD~ditiD~I D:e equ:ilib~i um oi par~lale~
in the adbesion la,ye~ 4 o~ t~e c,yli~drical p~ripheral surface ~f the r~-Abing dr~lm 3:
~d 3 ( JJ _ p ) cl,2f~ - r~, (4) or el~s, relabive t~ the diameber of ~ par~icle (~h~c~
latter i~ conditio~ll,y tske~ b~ be ~pherlcal~"
d = \~¦f~ ;" 2~ -~heres "d'~ he dismeter c~ a p~rb$cla (d = 2r);
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",P1" a~d "J~2 " ~re, re~pectiv~l,y9 the den~ity of the sol~d phass a~d ~f t~e liSIuid?
"~ s r~diu~ of rotatio~ ~ bhe part;icle~
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tha ~ac~ ~rlcb~on ~actor ~ the liqui~
tbe a~heslo~ er 4.
I1; ca~ be ~een ~rom expression~ (4~ and (5) b~ali tb~
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~15~6~7 -- 17 _ movement o~ a particle of a diameter "d" within the adhesion layer 4 a~d its expulsion from -this layer depend on -the den_ sity of -the dispersio~ medium, the radius 'IR" of -the circular path of ro-tation of the paxticle, the speed of its ro-tation and the value o~ the sur~ace tension o~ the adhesion layer 4.
~he radius o~ the circular path of rotation of the particle is de~ined by the diameter of the drum 3.
Increasing the diameter of the drulll 3 is limi~ed by bhe ~tructu~al consldera~ions and the Illanu~c-~uring ~omp7ex~t~.
~here~or~ bhe major par~me~r~ of the process o~ ~parR~io~
o~ tne solid phase in t~ drilling mud 2 on the rotating cy-lindrical surface of the drum 3 are the angular speed of its rotation and the value o~ the surface -tension o~ the adhesion la~er 4~
By varying the r.p.m. of the drum 3 and the value of the surface tension of the adhesion layer 4, it is possible to regulate within a broad range the process of separation o~ the solid phase in the drilling mud 2, so as to remove the surplus solid phase and -to retain the fine clayey particles which are the major colloid componen-t of a cla~ey drilling ~ud~ :
To remove the weighting material from -the drilling mud ~ -by its cen-trifugal separation, the solid rock cuttings are disin-tegrated, prior to the separation, -to -the particle size ~-of the weighting material. In this case the weighting material .
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6~7 ~ 18 -par-ticles of the speci~ic mass of 4 2 g/cm3 are separated f`rom the surface of the adhesion layer under an~ given condi-tions generally faster than the particles of sludge,which have -the same size but a lower specific mass (2.6 g/cm3). ~he purified ad-hesion layer 4 of the drilling ~ud 2 is scraped off b~ the scraper 7 ~nd directed in-to the receptacle 9 ~ o reduce the ~alue of the surface -tension and -to regu-late this value, low-voltage direct electric curren-t is made to flow through the drilling mud and the adhesion layer 4 from the direct-current low-volta~e source 12 via the ~ollowing circuit: negative terminal of the direct~current source 12 -electrode 10 - drilling mud 2 being purified - adhesion la-yer 4 - purified drilling mud 8 - electrode 11 - positive -ter-minal of the low-voltage direct-current source 12. The electro-de 10 thus acting as the cathode9 the electrolysis of salts contained in the purified drilling mud 2 within the receptacle 1 results in -the increasing pH value of the medium. As it is nown from drilling practice, this increase of the pE value reduces the surface tension. ~herefore, by varying the value o~ the low-~ol~age electric current flowing through the drillin~
mud, the value of the surface tension can be regulated.
~ nder the action of the flowing elec-tric current, charged particles are produced wi-thin the adhesion layer. ~o amplify -the inlDluence of the charge of the charged particle~ upon the `: :
~L5~7 sur~ace tension o~ the drilling mud in the adhesion la~er 4~
and to enhance the conditions o~ separation of -the solid phase particles of a certain mineralogical composi-tion in -the aahesion layer 4 ~ there are produced in the latter -the areas o~ high-voltage electric fields. ~he portion o~ the adhesion layer which is the area opposing the negatively charged electrode 15 is always charged positlvely ~rom the high-voltage source 13 along the circuit: positive terminal o~ the high-voltage direct-current source 13 - electrode 10 - drilling mud 2 to be purified - adhesion layer 4, ~he positive charge o~ the particles moving toward the e~ternal surface o~ the adhesion layer 4 provides for separation in this area~ to the greater degree, of neutral and positively charged particles (io e.
mainly OL the weighting material).
~ he other piortion of the adhesion layer 4, i,e. the area facing the positvely charged electrode 16 ls al~a~s charg~d negatively ~rol~ tne high-volta~e ~ource 14 via the eircuit:
nega~ve ~erminai of ~he ~lgh-~o~tage ~irec~-current source 14 - electroae 17 - puriYied ari~ n~ mud ~ - adhesion layer 4.
In this zone negatively charged particles o~ clay move toward the surface of the adhesion layer 4.
Under the action of the centri~ugal forces, the reduced surface tension and the high-voltage electric field, the charged par-ticles contained in the adhesion layer are expelled .
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;67 from this layer 4 into the respective sludge receptacles 17 and 18 arranged to underlie the respective electrodes 15 and 16. Some of the chargecl particles as far as the respective high-voltage electrodes 15 and 16 where they lose their charge and flow down the planes of the high-voltage electrodes 15 and 16 into the respective sludge collectors 17 and 18.
Therefore, the herein disclosed apparatus is operable to separate the drilling mud in a single process into three parts, Within the first area or zone, it is the weighting material that is predominantly separated.
Clayey rock particles are removed in the second area.
The third part is the drilling mud purified from the extra solid phase.
The sensor 19 of concentration of the solid phase, accommodated in the flow of the purified drilling mud 8 is used to maintain the optimum duty of the purifi-cation of the drilling mud 2, An example of implementation of the disclosed method can be provided by data obtained by a series of tests aimed at determining the optimum parameters of the operation of purifying the drilling mud 2. There were tested various drums 3 of diameters ranging from 100 to 500 mm, rotatable from 10 to 10,000 r.p.m. It has been found that with the drum 3 rotated at speeds from 1000 to 2000 r.p.m. the thickness of the formed adhesion layer 4 of the drilling mud of a viscosity from 10 :
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to lQO cen-tipoise is from 15 to 30 mm. Under the action of the low and high voltage supplied by the sources 12, 13, 14 o~
direct current there has been a-ttained satis~ac-tory puri~i-cation oL the drilling mud from sludge and removal o-f the weighting material.
~ hus, the herein disclosed method of separa-ting the solid phase in a drilling mud and the apparatus performing this method offer considerable technical advantages over purifying devices currently in use in the drillin~ operation.
By regulating the speed of rotation of the drum 39 by ~arying the values of the high and low direct-current voltage supplied, there is attained a high degree of the purification o~ the drilling mud at relatively low investment a~d operat-ing costs. ~he absence o~ complicated driving arrangements facilitates reliable per~ormance of the apparatus in an au-to-matic mode.
~ he economic e~iciency o~ implemen-ta-tion o~ -the present inv~n-tion is defined by the reduced cost o~ purif~ing -the dril-ling mud, reduced consumption o~ chemical agents and higher mech~lical drilling rates, owing to the enhanced quality of the purifica-tion of -the drilling mu.d.
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Claims (12)
1. A method of separating the solid phase in a drilling mud, including forming an adhesion layer from the drilling mud on a rotating curvilinear closed surface by partly projecting said surface into the drilling mud;
treating the drilling mud and the adhesion layer formed therefrom in a direct-current electric field to reduce the value of the surface tension in the adhesion layer, and simultaneously regulating the angular speed of rotation of the curvilinear closed surface to attain the required values of the centrifugal forces in the adhesion layer.
treating the drilling mud and the adhesion layer formed therefrom in a direct-current electric field to reduce the value of the surface tension in the adhesion layer, and simultaneously regulating the angular speed of rotation of the curvilinear closed surface to attain the required values of the centrifugal forces in the adhesion layer.
2. A method of Claim 1, wherein the drilling mud is treated in a low-voltage electric field.
3. A method of Claim 1, wherein the adhesion layer is treated in a high-voltage electric field.
4. A method of Claim 2, wherein the value of the intensity of the low-voltage electric field is varied, depending on the value of concentration of the solid phase in the purified drilling mud.
5. A method of Claim 3, wherein the direction of the high-voltage electric field is varied, depending on the mineralogical composition of the solid phase of the drill-ing mud.
6. A method of Claim 3, wherein the value of the inten-sity of the high-voltage electric field is varied, depending on the particle size of the solid phase contained in the drilling mud.
7. An apparatus for performing a method of Claim 1, comprising: a receptacle adapted to receive and contain therein a drilling mud to be purified; a driven drum accommo-dated above the receptacle adapted to receive the drilling mud to be purified, so that a portion of its external cylindrical surface extends into the drilling mud being purified, for forming thereon in the source of rotation of the drum an adhesion layer from the drilling mud being purified; a direct--current source and electrodes connectable thereto, adapted to produce an electric field in the drilling mud to be purifi-ed and in the adhesion layer, to reduce the value of the sur-face tension in the adhesion layer; a receptacle adapted to receive the purified drilling mud.
8. An apparatus of Claim 7, wherein one of the electrodes is accommodated in the receptacle adapted to receive and cont-ain the drilling mud to be purified, and another electrode is accommodated in the receptacle adapted to receive the purified drilling mud, the two electrodes being connectable to a low-voltage direct-current source.
9. An apparatus of Claim 7, comprising at least one electrode accommodated adjacent to the cylindrical surface of the drum, adapted to carry the adhesion layer, and at least one high-voltage direct-current source having its one output terminal connected to the electrode accommodated in one of the receptacles for the drilling mud, and its other output terminal connected to the electrode accommodated adjacent to the cylindrical surface of the drum, adapted to carry the adhesion layer, at a spacing in excess of the high-voltage breathrough air gap.
10. An apparatus of Claim 9, wherein the electrode accommodated adjacent to the drum is shaped as a portion of a hollow cylinder having its concave side facing the drum.
11. An apparatus of Claim 8, comprising a sensor adapted to produce a signal representative of the con-centration of the solid phase in the purified drilling mud, accommodated in the receptacle adapted to receive the purified drilling mud and having its output connected through a regulating device to the input of the low-voltage direct-current source.
12. An apparatus of claims 9 or 11, wherein the sensor adapted to produce a signal representative of the concentration of the solid phase-in the purified drilling mud is connected to the input of the high-voltage direct-current source.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000352090A CA1150667A (en) | 1980-05-16 | 1980-05-16 | Method of separating solid phase in drilling mud and apparatus for performing this method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000352090A CA1150667A (en) | 1980-05-16 | 1980-05-16 | Method of separating solid phase in drilling mud and apparatus for performing this method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1150667A true CA1150667A (en) | 1983-07-26 |
Family
ID=4116969
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000352090A Expired CA1150667A (en) | 1980-05-16 | 1980-05-16 | Method of separating solid phase in drilling mud and apparatus for performing this method |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1150667A (en) |
-
1980
- 1980-05-16 CA CA000352090A patent/CA1150667A/en not_active Expired
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