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KHOA HOC VA CANG NGHE MO \NGHIEN ClJU MOT SO GIAI PHAP CONG NGHE KY THUAT NANG CAO TY LE MAU THAM DO URANI KHU Virc pn Lirn pn RONG, OURNG NRM Du dn thdm dd qugng urani khu Pa Lua Pa Ring, Nam Giang,[.]
KHOA HOC VA CANG NGHE MO \NGHIEN ClJU MOT SO GIAI PHAP CONG NGHE-KY THUAT NANG CAO TY LE MAU THAM DO URANI KHU Virc pn Lirn-pn RONG, OURNG NRM TS PHAM QUANG HIEU Trwdng D%i hgc Mo-Dia chat u dn thdm dd qugng urani khu Pa Lua-Pa Ring, Nam Giang, Quang Nam duoc thuc hi$n vdi vdi nhi$m vg Idm rd elu trdc dja chit mo, khoanh djnh ehi tilt dly du cdc thdn qudng Xdc djnh tru luong, chat luong qudng, dde dilm phdn b l qudng urani Trong dd, cdng tdc khoan lly mlu duoe thuc hipn tren todn bd chiiu sdu cde l5 khoan thdm dd Do dac dilm dat dd vCing thdm dd tuang doi phuc tap, thdnh phin chu yiu la dd cdt kit, bdt kit phdn Idp vd nut ne mgnh, ding thdi vi$e dp dgng quy trinh ky thudt, cdng nghe lly nilu cdn nhilu bgn chl, nen cdng tdc khoan thdm dd lly mau trudc ddy chua dgt ty 10 mlu theo ydu clu Chinh vi vdy nghien cuu cde giai phdp cdng nghd ndng cao ty Id mlu d nhdng l6 khoan ndy mang tinh d p thilt vd ed y nghTa thuc tien sdu sdc D Khal quat v l cdu true dja chdt khu vuc tham dd, anh hirdng cua chung d i n cong tac khoan lly mdu Qua tdi li^u dja chit vd tdi li^u khoan eho thdy, ddc dilm i^a ting chda qudng urani khu Pd LuaPd Ring gIm cdc da cupi kit, sgn kit, cat kit, bdt kit Id chu yiu (Chung Id logi dd manh vgn cd dd cung td cdp VI din cip IX theo dd khoan) Su phdn b l chuyin tiip ede Idp theo quy ludt ehung eua qud trInh thdnh tgo trim tich Chieu sdu ehua qudng ndm khoang td m den 150 m theo chiiu sdu l i vdi ddc dilm cua cde logi dit dd cat kit, bdt kit, niu khdng ehju anh hudng cua cac phd hiiy kiln tgo dja chit thi cdng tdc khoan lay miu se gSp nhilu thu$n lpi nhu tic dd ea hpe, chit luong vd ty 10 mlu eao Tuy nhidn, chju anh hudng eua cdc phd huy kiln tgo dja chit Idm eho dit dd khu vuc thdm dd nut ne, vd vgn Idm dnh hudng rit nhilu din cdng tdc khoan, nhit Id hi$n tupng mit dung djch, s^p id thdnh l6 khoan chit lupng va ty Id mlu giam Trong trudng hap ndy van d l dp dyng chl dp cdng nghe khoan, su dung dgng cu pha huy vd nhat Id ky thuat chen giu cung nhu keo mau phai chuan xae d l dgt duoe chdt luong tT 1$ mdu cao Dd cudi kit, san kit d day chi chilm khoang tu din % tram tich chua qudng Thudng phdn b l d chieu sdu tu 50 m den 150 m Thanh phan chu yiu Id cupi thgch anh cd kieh thudc tu 0,4 din cm Thanh phan xi mdng gdn kit Id sdt serixit vd chlorit Niu XI mdng gdn kit yeu, tuc Id luc gdn kit tilp xuc giua xi mdng vd cae hdn cudi yiu thudng gdy hien tupng bong trdc cd chin dpng nhu dpng dit, nd ho$c ede hogt dpng kiln tgo khdc Khi khoan qua logi dd ndy thudng ggp nhung khd khdn, nhu cuOi de bong khdi xi mdng gdn kit md khdng dupe mdi cdt dudi tde dgng cua mui khoan, k l ca tde dung nhp Nhung hdn cuOi ndy khdng dupc nudc rua ndng Idn mdt dit dupe, chdng ndm din dudi ddy l5 khoan, gdy xdc vd va d|ip manh khoan ctio din bi ddnh dgt vao thdnh lo khoan Niu thdnh l5 khoan kem I n dinh se bj sgp Id, md rpng dudng kinh, tao hdm Ich Mgt khde, tieu hao mui khoan trudng hop ndy rit Idn cdc hgt cdt cua ludi khoan chua tham gia vdo qud trinh phd huy ddt da dd bj gay hit Ding thdi, chit luong mau kem, ty Id mlu thip Cdt kit Id logi dd phi biln, chilm tdi 95 den 97 % trim tich ehua qudng tgi viJng nghien cuu Do nguin trim tich edt ed du cde cd hgt ndn cdt kit hidn didn d ddy ed ea cdt kit hgt mjn, hgt trung vd hgt thd ChUng thudng cd mdu xdm ndu din xdm sdng Thdnh phin thgch anh chilm td 50 din 80 %, cdn Igi id cdc vgn qudczit, felspat, plagiocia, silic vd cdc phin khdc Xi mdng gin kit chu yiu Id sdt serixit vd chlorit hode cde v$t chit huu CONG NGHIEP MO SO - u^ KHOA HOC VA CONS NGHE MO ca kliu xi mdng ca sd l i p day hogc tilp xUe Khi khoan vao loai cdt kit co cdu tgo dgng khii, bin vung, dp bin chiu ndn cao thi khoan d l dang han nhilu so vdi vao cudi kit, san kit va cho ty le mau cao k l ea khoan hiep ddi Tuy nhien, dja tdng d day nhu da neu d tren deu nlm viJng ed nhilu pha huy kiln tao, nen da cdt kit cung bj nut ne vd vgn nhilu Do dd, vide khoan va lly mSu eung gap nhilu khd khan Ldp ddt phu ed chiiu day khong diu, chd ddy nhit tu din m, c h l mdng nhdt chua tdi Im Thdnh phdn gdm set pha, cat pha ldn sgn sdi, cd chd cd ea cupi Idn va nho Ddt phu cung la Idp ddt kem I n dmh, ty lp sgn sdi chilm khoang 15-30 %, edn cupi chi khoang din % Ldp da phong hda, ban phong hda, phdn b l d dp sau tu 1,5 m din 20 m, phin chu y i u Id thach anh, felspat, vgn dd quaczit, Idp ehua quang urani Khi khoan vdo idp ddt thu'dng hay bi sap Id vd mit dung djch, phai chong dng gia e l thdnh id khoan Mot s6 bien phap cong nghe-ky thugt nang cao ty le m i u tham Urani tai khu virc 2.1 Lwa chgn ong mau cho vting tham Cho din khoang 5-10 nam v l trudc, vi thilu chung iogt nen cdc dan vj thi cdng khoan thudng su dung dung ey Idy mau khdng theo quy chuIn, ed loai Ing mau ndo thi su dgng loai Ing mau do, ehu ydu Id su dyng cac Ing mdu dan, dng mdu bam tia Tuy nhien, nhdng bd Ing ndy eho ty Id mdu thdp Hidn nay, vdi xu t h i phat triln cua khoa hpc cdng nghe, tai khu vuc ttiam dd mdt so dan vi dd dp dung edng nghp khoan bdng dng mau kep Viec su dgng dng mdu kep da dem Igi hieu qua edng tae lly mdu Tuy nhidn, cd thi tu nhilu nguyen nhan nhu lua chon loai Ing mdu kdp, logi mui khoan, quy trinh su dyng, c h l dp cdng nghp khoan md ty 1$ mlu trung binh khu vue thdm dd vdn chua dgt theo yeu elu eua d l dn d l Vi vgy, phgm vi bao edo, ehiing tdi chi d l cap din cac loai dng mdu kdp Trong khu vue nghien cuu, da su dung cac logi dng mdu kep sau: 2.1.1 6ng mau kep T2-76 (Thuy Diin) Nguyen ly Idm vide eua nd la dng khdng chuyen dpng nhd goi tua I bi Vi vgy, han chl duoc cae tae ddng ca hpc Nudc rua di qua khe hd giua Ing vd dng ngoai, khdng true tilp chay vao mau BO phdn chen mau gIm mdt Ing chda hom chdn, duoe vgn vao Ing bdng ren trdi Hom chen duoe ddt bp phdn cua dng chua hom chen Khi khoan mau vdo Ing chda hom vd hom Chen duoc dly len Khi keo mau, Ing mdu dupc ndng len, hom chen tyt xuIng chen chdt miu WM CONGNGHllPMOSf 4-2013 Vdi nhdng uu dilm v l cdu tgo cQng nhu nguydn ly lam viee eua Ing mdu T2-76 dd dem lai kit qua t9 10 miu d i t da nut ne, d#p vd d mo urani Pd Lua-Pa Rong tuong d l i cao (90-^95 %) Dgc biet, da it ndt ne ty Id miu cd t h i ti> 95-^100 % Nhuoc dilm cua logi ong miu ndy la gid thdnh cao han rat nhieu so vdi cdc logi ong mau kdp eua Trung QuIc 2.1.2 Ong mau kip TDN-76-1 (Uen X6 cQ) v l nguyen ly lam vide gidng Ing miu kep T276 Loai Ing TDN-76-1 ed mpt sd nhuoc dilm sau: • He thing I dd cdu tgo dp chinh xac it eao, gdy nhao lam Ing bj lie dao, tao dilu kipn mdu bj vd va chdn miu qud trinh thu nhdn miu; •:* Mlu sot Igi d day nhilu, Ing khdng ddng tdm vdi Ing ngoai; • Do khoang edeh dai nen thdi gian tao mdu, mlu ehju nhilu tdc dpng eua nudc rda vd va dap mdi mdn ca hpe, cd t h i miu bj rua lua ; • Do hp thing true g i i dd cd chiiu dai Idn va blng bgc, bdi tran bdng dung djch khoan, bdi vgy du chdt nudc rua tdt thi ho thong I da eung bj mdn nhanh, gdy nen su dao trge, hai Ing khdng ding tdm va dgp Mau khoan van chju tdc dpng co hpc nhu ing mlu dan 2.7.3 Ong mau kep Trung Quoc Nguyen ly lam vide tuang tu Ing mau T2-76 va TDN-76-1 Khi khoan ddt da nut ne mgnh, ty le mdu khdng eao, miu khoan bj chdn vd dap vd Nguyen nhdn la khe hd gida Ing va Ing ngodi qud Idn, Khi l5 khoan bj nghieng, ban than ong vdi trpng iuong cua nd se nghidng di mpt gdc nao dd Trong trudng hop ndy ong vd ong ngodi khdng ding tam vdi Qng chda mlu ti vao mui khoan va theo lue ly tam, hai Ing cung chuyin dpng Viec c h l tgo thilu chinh xdc, sai s l ldp ghdp Idn, la nguyen Idm cho Ing bi dao, gay l#ch tam qud trinh khoan Thuetl d vung nghien euu, I n g mau chi cho ty 10 miu trung binh 85 % Tdm Igi, bp Ing mdu Trung QuIc c6 nhilu nhuac diem, chi eo the khoan dit da vd khoang san ddng nhat, nguyen khii, it nut ne Vdi dgc dilm dat dd vung thdm dd bO ong mlu ndy kh6 cd the eho ty 10 mdu theo ydu clu (> 90 %) 2.1.4 Chgn lo^i ing mau kip cho vOng thim dd Tren ca sd phan tich d§c dilm elu tgo, nguydn ly lam vi0c cua mdt s l Ing miu kdp; d|ic dilm dilu kien dja chit vd thue t l san xuit d vung thdm dd, vdi nhung uu dilm n i l tr0i cua Ing miu T2-76 cua Thgy Diln san xuat, tde gia d l xuit lug chpn logi ong miu ndy d l khoan KHOA HOC VA CiNG NGHE MO D I hgn chl mng dOng, ta ehpn ong miu ed chiiu ddi m, dudng kinh ngodi Ing miu 73 mm, dudng kinh cin khoan 50 mm 2.2 Lwa chgn che dg cong nghg khoan cho vung tham Sau lua chpn duoc trang thilt bi phu hop vdi ddc dilm cua dit dd, ehung ta phai nghien cuu lua chpn chl dO edng nghd khoan hpp ly d l dgt duoc mgc tidg ndng eao ty 10 miu C h l dp cdng nghd khoan khoan xoay lly miu cd nude rua gom ede thdng so: tai trpng chieu trge; s l vdng quay; luu luong vd chdt luong nude rua 2.2.1 Tii trgng chiiu tnic (P) Khi khoan vdo dat dd, khodng san nut ne, cung mem xen kpp, tai trpng chiiu trge dupe xde djnh theo cdng thde: P=p.F.C (kG) (1) Trong dd p - Tai trpng len cm^ dien tich be mgt cua mOi khoan, kG/em^; F - Dipn tich b l m$t lam vi0c cua mui khoan, cm^: F = j(D^-d^l-T.l.n ,2, _^^ Ap dgng cdng thuc (3) tinh toan tren kit hap vdi tham khao tdi Ii0u ly thuyit, tdi lieu thue t l san xuit chdng tdi d l xuit tie dp vdng quay d l khoan khu vuc thdm d6n=71 -5-310 v/ph Khi khoan vdo ddt dd dd nut ne edng mim xen kpp cdn cd su phdi hap chat ehe pida n va P Dae bi0t ddt dd nut ne mgnh, edn giam s l vdng quay va giam tai trpng len mOi khoan khoang 40 -5-50 % vi dd nut ne tang thi dp ben ca hpe giam, giam duac cdng suit tieu thg cua mdy 2.2.3 Luu lugng vi chat lugng nudc rda (Q) Luu iupng nude rda (Q) duoc xde djnh theo cdng thde: Q-m-(D2-d2).v,l/ph (4) Hoac theo kinh nghiem: Q=(qo.D), 1/ph ^ ^ ^ (5)^ Trong dd: m - He so k l din su khdng dong diu cua tie d$ ddng chay tilt dipn l l khoan khdng diu va khe nut (m=1,1-^1,3); D - Dudng kinh Idn nhat cua lo khoan, m; d - Dudng kinh ngoai cua edn khoan, m; po- Lupng nude rua dung cho 1cm dudng kinh ludi khoan, qo=4-^6 l/ph.cm Tgi ddy: T - B l ddy Idp matricx, cm; I - Chiiu dai Td tren ta xdc djnh dupe luu luong nudc rua can rdnh thodt nudc, cm; n - S l rdnh thodt nude; D, d thilt khoan bdng mOi khoan kim cuang dudng Dudng kinh ngodi vd eua mui khoan; C - He kinh 76 mm cho khu vuc thdm dd Id: Q=30^0 l/ph s l k l din dO ndt ne cua d i t dd (da it nut ne C=0,9; Trong dit dd, khodng san nut ne, phdn Idp xen dit dd nut nd C=0,8; dit dd ndt ne mgnh C=0,7; kep, khoan bdng mOi khoan kim cuang vdi bO Ing dit dd ndt ne mgnh, xen kpp C=0,6) mau kdp, ehdt luong nudc rua ddng vai trd rat Vdi dudng kinh ngodi mui khoan Id 76 mm ta quan trpng Ddc bipt, chdt lupng dung dieh phai tinh dupc: dd it ndt ne F=13,42; dit dd ndt ne bao v0 dupe miu khoan vdo Idp dit dd mem, F=15,42; dit dd ndt ne mgnh F=17,42; dat da nut gdn kit yeu ne mgnh, xen kpp F=18,03 Gid tri tai trpng len Chit luong dung djch khoan khoan kim lem^ cua F duoc xde djnh nhu sau: ddt dd cdp cuang cin ddc bi0t quan tam Trong dd, can VIkVIII - 52-^70 kG/cm^; IX^X - 70^105 kG/cm^; nghidn cdu viec sd dgng dung djch pdlime Khi cho XI4-XII - 87-^140 kG/cm^ Nhu vdy, tai trpng chiiu pdlime vdo dung djch (ham lupng thdp) se giam trge dp dgng cho vUng nghien cuu khoang tu nhilu tin thdt dp luc d chl dp chay rot (Hipn tupng 500^800 kG ndy rit cd hi0u qua d l i vdi Ing ed dudng kinh be) 2.2.2 S6 vdng quay (n) Ddt bipt Id ong mlu kep, Ing miu luon Ngodi tdc S l vdng quay dit dd ndt ne duoe xde dyng giam dp luc, pdlime cdn ed tdc dgng giam luc djnh theo cdng thde: ma sdt giua thdnh lo khoan vd bd dgng eg khoan, tgo mdng bpe xung quanh ldi khoan, tdng tic dp truot cua bO khoan eg, ching hipn tupng mit nudc dit da nut ne Trong dd A - Cdng cin thtit cua mOi khoan kim Trong khu vuc nghien cdu, loai pdlime dupe pha cuang d l phd huy dd, d l i vdi ed hgt 30-^90 hgt/eara thi A=0,018-^0,020 KJ; M - S l hgt kim vdo dung dich sdt, cd nhan hipu Quick mud (Australia), ty pha chl 0,7Si-1 lit cho 1000 lit nudc la, cuang trdn mOi khoan; P - Tai trpng chiiu tryc Idn mOi khoan; D - Dudng kinh mui khoan kim cuang; 2.3 Cac giai phap chung ve ky thu$t va cdng K - H0 s i dO edng ciJa dd vd kich thudc kim nghg de nang cao ty 1$ mau vung tham dd cuang; (p - H0 s l du tru d | ben kim cuang (1,5-^2); Trong khoan kim cuang, nen chpn clu tnic lo > - H$ s l k l din su tdng tai len mui khoan ein khoan dan gian nhit (l5 khoan it d p dudng kinh khoan rung (1,2-;-1,5); At - Thdi gian tdng luc edt td nhit, it ching Ing nhit) Tuy nhidn, can d0c bi0t din t l i da (s) COI trpng gia c l thdnh l6 khoan I n djnh vd bin CdNGNGHl|PMOSd4-2013 ^^_ KHOA HOC VA CONG NGHE MP vung Cdch t i t nhat d l i vdi tang kem I n djnh, de sap Id, mdt nudc nen chpn bi0n phdp chdng ing, trdm xi mdng Cdn eu vdo cpt dja tdng vung nghien cuu, thilt ke cau trUc cho Id khoan duoc trinh bay tren hinh Trang bi may khoan phai dam bao tie dp quay cua bp dpng eg khoan kim cuang dgt duoe eao nhdt, dong thdi cdng suit lam vi0e cua may phai phU hpp vdi chiiu sdu lo khoan thilt ke Trong qud trinh khoan may phai dupe kit elu vdng chic Mdy khoan phai day du cae ding h i kilm tra nhu: dong h i bao dp suit he thing thuy luc, trpng luong bp dgng cy khoan, dp luc bam ChiJng tdi d l xuit su dyng may khoan dupe eho vCing nghien cdu Id cac logi: XY-1A; GX-1TD; GK-180 Khoan md Id tiln hanh khoan vdi t i c dO vdng quay nhd, nudc rua trung binh d l dam bao hudng dl cho Id khoan Sau dd, dung ong chdng d l gia c l thdnh l5 khoan tang khdng I n dinh (0^20 m) Khoan bdng mui khoan kim cuang dupc tiln hdnh mpt each thgn trpng Chi duoc tha mui khoan xuong ddy nao lly hit cac cgc mlg edn sdt Igi tu hipp khoan trudc Khi tha dyng eg, cdn chg J nhung dilm ma dudng kinh lo khoan thay dli, l l khoan bi vudng da chia Tha bd dyng ey cdch ddy 20cm phai dCjng trge spinden cDa mdy kit hap quay va rua, sau dd mdi dat mui khoan Idn ddy Trong qud trinh khoan, hgn chl viec ndng bd dgng eg len khdi ddy, chi ndo tiln dp khoan chdm so vdl tiln dO binh thudng vd dp suit mdy bam tang (ed hidn tuong chdn miu) mdi ndng bd dgng eg len khoi day 5-^10 cm d l khle phgc hi0n tuang chen mau Khoan ddt da nut ne, cung mim xen kpp thudng xuyen xay hi0n tuong chen mdu Vi vay cin dp dung c h l dp khoan ddt da nut ne, niu mdu vdn bj chdn thi tiep tuc giam s l vong quay, tai trpng chiiu tryc tu 20^30 % so vdi thilt k l vd nen thuc hi0n hi0p khoan ngin Khi chen miu, nang bp dgng eg len 2-f4 em, co clu chen mdu eua Ing mdu kep la hom chdn nen ndng hom chdn se tgt xudng dm chat miu kit hpp quay nhp cdn d l miu tu gay Khi keo miu va thdo cdn, phai hit sue nhe nhdng tranh va dgp manh lam rai mau Ludn kilm tra cdn than d l xdc (^nh iuong mau edn sdt lgi va hi0p sau phai thgn etiyp miu vdo Ing mlu mdi tilp tyc khoan Sau moi hipp khoan phai kilm tra cin thgn dudng kinh cua mui khoan, cdc hi0n tup-ng hu hdng cua mui khoan phai duoc xdc ffinh lai vi0c lua chpn mui khoan vd dilu chinh c h l dp khoan Cung vdi mui khoan, cdn chU y kiem tra cdc chi tilt md rdng trdn vd dudi Trong trudng hop cac chi tilt md rpng bi mdn qua quy djnh, eac Idp hap kim bj bong ra, rgn ndt thi cdn phai thay mdi De han c h l hien tuong kpt mun khoan d khe hd giua dng va dng ngodi lam cho dng quay theo ong ngoai hode bi nudc rua, can phai thudng xuyen kilm tra chit luong dung djch, idm sach mun khoan l i n dung djch Nen giam dp nhdt dung djch dilu ki0n cho phdp Thudng xuydn kilm tra bp Ing miu kep v l dp chinh xac, qua vi0c kiem tra dp ddng tam cua ong mdu trong, silt Igi cac e cu ham, kiem tra dp re mdn cua cdc vdng bi, ludn dam bao vdng bi dupc bdi tran vd chuyin ddng nhe nhang K i t qua dp dung thi^c t l 3.1 Dieu kien thyc nghigm Nhdm nghien cuu cdng vdi Dodn dia chat 154 da thue hipn Id khoan H008 tham dd qu^ng urani khu Pd Lda-Pd Ring vdi chiiu sdu 140 m Dia ting du kiln nhu sau: • Td 0^2 m: D i t phu phan gIm cat ket, bdt kit, bd rdi • Td 2^20 m: Od b0t kit, ban phong hda, nirt ne, phdn Idp day • Td 20-^140 m: Od cdt kit, bdt kit cung ehdc, ed lin san cupi nhd, nut ne mgnh, eau tgo xen kpp phdn Idp (Tu 50 m xuong, d i t da d p VklX theo khoan) 3.2 ciu true lo khoan Tren ea sd cdc yeu t l dilu ki0n dja chit va ydu clu nhi0m vg {muc dich) eua lo khoan; edng ngh0 khoan dp dgng d l thi cdng lo khoan, kha nang eung d p thilt bj, vat tu ddp ung eho thi cdng; dam bao hidu qua kinh te Td 0•^20 m dudng kfnh l5 khoan O 93, ching ong (p 98; tu 20-^140 m dudng kinh Id khoan O 76 3.3 Thdng so chi dg khoan Cdc thdng s l c h l dO khoan vd thdng s l dung djch khoan duoc dp dung theo Bang 1,2 Sang Cic thong so chi khoan Dilu ki^n dp dyng I-: VII (0+20m) VN- IX (20+ 50m) Vk IX p o - 140m) U Duong kfnh ngoai mui khoan (mm) 86 76 76 "QHlEPMOSdt-ZOIS p, kff"~" 500 + 600 700 +800 700 +800 n, v/pn 71 + 182 182+310 182+310 u , I/pn 30 40 + + 40 60 40 + 60 1} I KHOA HOC VA CONfi NGHE MO Sang Cic thdng s6 dung djch khoan Didu ki£n dp dung 1+ VII (0+20m) ^ ^ V l + IX (20+ 140m) y, kG/cm' 1,05+1,1 1,05 B, cmVao' 10+12 10+12 3.4 Kit qua d%t dwgv Tie dO ea hpc khoan trung binh: tu 0-^20 m: 2,8 m/h; tu 20-^40 m: 1,8 m/h Ty 10 mau dat trung binh: 93,5 % Kdt luan va kien nghj • Trong ddt da, khoang san ndt ne mgnh vd edng mim xen kep vi0c lua chpn ong miu kdp kilu ong khdng quay, Ing ngodi quay cd anh hudng rit Idn den vi0c ndng cao ty 10 miu khoan; • Thue hi0n dung quy trinh ky thugt khoan kim cuang khdng nhdng tdng ty 10 miu ma cdn tdng tuoi thp cua bp dgng eg khoan eg t h i la dng mlg vd mui khoan; • Trong tung dilu kipn ey t h i eua dat dd, ty 10 thu hoi mlu vin chua cao (