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Tuygn tap bao cao Hgi nghi KHCN "30 nam DSu khi Vift Nam Cff hdi mdi, thach thde mdi" 207 MOT SO KET QUA PHAN TICH DANH GIA LAI KET CAU GIAN KHOAN BIEN CO DINH PHUC VU CONG TAC KHAO SAT, DUY TU BAO D[.]
Tuygn tap bao cao Hgi nghi KHCN "30 nam DSu Vift Nam: Cff hdi mdi, thach thde mdi" 207 MOT SO KET QUA PHAN TICH DANH GIA LAI KET CAU GIAN KHOAN BIEN CO DINH PHUC VU CONG TAC KHAO SAT, DUY TU BAO D I T O N G VA SIJ^A C H C T A CUA XNLD VIETSOVPETRO Hoang Le Ngge VTnh, Bui Van Ngan Vu Xuan Lai, Tu Le Trung XNLD Vietsovpetro TOM TAT Hdu hit cdc gidn khoan biin cua XNLD Vietsovpetro deu da sir dung tren 10 ndm (tudi thg mdi thiit ke du kiin Id 25 ndm) Trong diiu kien mdi trudng biin khdc nghiet, sau nhiiu ndm sir dung, nhiiu yiu td dnh hudng ddn din su khdc biet giica khd ndng chiu luc ciia kit cdu theo thiit ki vd thuc ti hien trgng cdng trinh Mat khdc, cdc gidn cd dinh dgng MSP ciia XNLD Vietsovpetro cd hucmg cdng trinh, dp sdu nuac, diiu kien dia chdt khdc nhung diu dugc xdy dung theo mpt dgng thiit ki diin hinh Vien Thiit ki Ddu biin Baku (Lien Xd cii) thuc hien tic ndm 1980 Trong dd, tinh todn mdi vd kiem tra niit chua dugc di cap din Chinh vi vay, di ddm bdo an todn cho cdc cdng trinh, viec phdn tich ddnh gid lgi khd ndng chiu luc ciia kit cdu gidn khoan biin Id yeu cdu cdp thiet nhdm phuc vu cho cdng tdc tu vd bdo duang Bdo cdo trinh bdy kit qud phdn tich ddnh gid lgi kit cdu chiu luc cua mpt sd gidn khoan biin ciia XNLD Vietsovpetro, tic dua cdc kit ludn vi khd ndng chiu luc cua nhimg cdng trinh ndy Tren ca sa nhicng tinh todn cu thi, bdo cdo dua mpt sd kit ludn gdp phdn hodn chinh cdng tdc phdn tich ddnh gid lgi kit cdu chiu luc cdc gidn khoan biin ciia XNLD Vietsovpetro, dd nhdn mgnh din phuong phdp tinh todn dp bin giai hgn tren ca sa phdn tich phi tuyin kit cdu chiu luc kit cdu gidn khoan QUY TRINH PHAN TICH DANH GIA LAI Phan tich danh gia lai (PTDGL) ket eau chju lye gian khoan la nham xac djnh cac dac trung ve hien trang ky thuat cua ket cau tai thdi diem danh gia va so sanh sy phu hgp cua chung vdi mye dich su dyng hay tieu chuan quy djnh Ap dyng quy trinh PTDGL theo quy pham API-RP-2A [1], tren co sd dieu ehinh phu hgp vdi cac dac diem eua gian khoan cua XNLD Vietsovpetro, quy trinh PTDGL gdm bude chinh (Hinh 1): L Lya chon gian de PTDGL Viee lua chgn gian de PTDGL can dya tren cac dae diem sau: - Thdi gian su dyng cdng trinh vugt qua tudi thg mdi thiet ke - Cd hu hdng hay suy giam kha nang chju lye cua cae phan tu ket cau chinh - Cd sy thay ddi dir lieu thiet ke hay cac lan danh gia trudc nhu: Tang ngudi hay thiet bj tren gian Tang tai trgng tae dyng len ket cau 208 Mdt so kgt qua phan tich danh gia lai kgt cau gian khoan bign cd djnh phuc vu edng tac khao sat Phat hien ed eae khuyet tat hoae thay ddi kit qua khao sat, hay tinh toan thay cd sy hu hdng tdn thuong tieh luy, v.v Phan loai gian Can xac djnh gian can PTDGL thudc loai nao, tu dd ap dyng cae tieu chuan danh gia phu hgp Theo [1] gian dugc phan loai theo cac tieu chi sau: - Theo sy an toan ddi vdi ngudi: L1: Gian cd ngudi d, khdng so tan dugc L2: Gian ed ngudi d, so tan duge L3: Gian khdng cd ngudi d - Theo hau qua neu cd hu hdng: L1: Hau qua ldn L2: Hau qua khdng dang ke Lira chon gian de P T D G L i Phan loai gian X em xel cac dur lieu phuc vu P T D L Khdng K h o n g can d a n h gia Dat Gian duoc danh gia 1) A T Dal G i a n duoc danh gia D A T T i n h toan p h a n tich d a n h gia i PhSn tich theo m lie ihict kc' i Cd Khdng dat ^^— BiCn phap^^"^^.^ "'*"'' s ^hic p h u c T ^ - ^ ^ ' JTK hong 4.2 Phan lich theo dd b i n gitVi han i K h d n g dai Cd _^^ss=^^^^S Bien phap^^;;^;^,^ k h i c phuc? Khong G ian d u g c d a n h gia K H O N G » A T Hinh 1: Sff quy trinh PTDGL Xem xet cac dir lieu phuc vu PTDGL Cac dir lieu phye vu PTDGL cin phai dugc xem xet gdm: Tuygn tap bao cao Hdi nghj KHCN "30 nam Dau Vift Nam: Cff hgi mdi, thach thde mdi" 201 - Cac sd lieu thiet ke: vj tri, sau nude, dja chat, dieu kien tugng hai van v.v - Cac sd lieu khao sat bao gdm: eae ket qua nhan duge tir khao sat eho phin thugng tang va phan ket cau chju luc cac sd lieu ve cdng tae tu, bao dudng, sua chira v.v Tinh toan, phan tich va danh gia Viec tinh toan, phan tich ket eau dugc thyc hien theo bude sau: - Bude 1: Phan tieh theo muc thiet ke: giai quyet cac bai toan ket cau tuyin tinh (vat lieu lam viec mien dan hdi, quan he giira img suat va bien dang la tuyen tinh) - Bude 2: Tinh toan, phan tich theo ben gidi ban: giai quyet cac bai toan kit eiu phi tuyen (vat lieu lam viee mien dan deo) Tu bude tinh toan phan tich thir eho phep ta dang gia duge kha nang lam viec ngoai gidi ban dan hdi tai trgng vugt tai trgng thiet ke hoae sy bu bdng cua kit ciu ma cdng trinh chua bj syp dd (Hinh 2) Hinh 2: Sff mien dan hoi va mien deo ciia vat lieu thep fl Tinh todn, phdn tich theo mirc dp thiet ke Tinh toan, phan tieh theo muc thiet ke dya tren co sd phan tich tuyen tinh ket eau bao gdm: • Tinh todn, phdn tich theo trgng thdi giai hgn cue hgn (ULS) Tinh toan, phan tich ket cau theo ben, dn djnh, kha nang chju lye cat, ap lye thuy tTnh cua cae phan tu ket cau va cgc dieu kien khai thae, dieu kien bao cyc ban 100 nam, sy tac ddng cua ddng dat vung cd nhay cam, v.v Viec tinh toan, phan tich theo trang thai gidi ban la so sanh he sd su dung eua nut, phan tu vdi cae gia tri cho phep • Tinh todn, phdn tich theo trgng thdi giai hgn mdi (FLS) Tinh toan, phan tieh ket cau tich luy tdn thuong dudi sy tac ddng cua tai trgng mdi trudng theo cac chu trinh ngau nhien sudt ddi sdng cdng trinh Ket qua cua tinh toan theo trang thai gidi ban la dua duge tudi thg mdi eua cac nut, tir dd so sanh vdi tudi thg cho phep • Tinh todn, phdn tich theo trgng thdi gidi hgn phuc vu (SLS) trang thai chi tieu danh gia chu yeu la chuyen vj eua ket cau khdng dugc vugt qiia gidi ban cho phep Khi ket qua tinh toan, phan tich theo miie thiet ke khdng dam bao thi can tien hanh tinh toan, phan tich theo ben gidi han 210 Mdt so ket qua phan tieh danh gia lai ket cau gian khoan bign c6 djnh phuc vu cdng tac khao sat b Tinh todn, phdn tich theo dp ben giai han Tinh toan, phan tieh theo ben gidi ban dya tren co sd phan tich phi tuyen ket eau theo trang thai gidi ban pha buy luy tien (PLS) Trang thai PLS danh gia kha nang ehju lye cua ket ciu qua he sd cudng du trir tdng thi cua ket cau RSR Ddi vdi ket cau cac gian khoan bien cd djnh thi anh hudng cua tai trgng mdi trudng ma dae biet la sdng va ddng chay la quan trgng nhat, vay gia tri SRS dugc xac djnh nhu sau: RSR= Gia tri luc ngang ldn nhat ket cau sup dd '-^ ^-^ ^ ; Tai trgng mdi trudng vdi tan suat xuat hien 100 nam Tren co sd phan tich phi tuyen ket cau chju lye bang each tang tai trgng timg muc, din tdi sy lam viec cua ket cau d mien phi tuyen (ke den ea phi tuyen hinh bgc va phi tuyen vat lieu), qua trinh tai mdt sd phan tu nguy hiem se hinh cac khdp deo va mat kha nang ehju lye lam cho ket cau bi syp dd Tu ket qua dd ta xac djnh dugc he sd eudng dy trii RSR Ket qua tinh toan theo phuomg phap the hien sat thye sy lam viec cua ket cau, dac biet la cac phan tu cd khuyet tat nhu mdp, meo, cong, v.v tir dd danh gia dugc kha nang lam viec tdi da cua cac phan tu ket eau mien dan deo Phan tieh ben gidi ban theo trang thai gidi ban PLS la bai toan phue tap lien quan den ly thuyet vat lieu lam viec mien dan deo, co hgc pha buy (md hinh hoa cac khuyet tat) va phuong phap xac djnh he sd dy trii RSR cua ket cau Dudi day la mdt sd dang md phdng dac trung su dung cho qua trinh phan tich danh gia ket cau edng trinh bien cua XNLD Vietsovpetro • Vdt lieu ldm viec giai dogn ddn deo Xet phan tu ehju tai trgng (Hinh 3), phuomg trinh mat dan deo cua vat lieu phin tu: r=/ N_ N Q, M, M^ ^yP M, ^ -1 r = 0: Ung suat phan tu nam d mien chay deo; F = -I: Phin tu khdng chiu luc Trong dd: A^, Qy, Q,, M,, My, M, la lye dge, lye eit, md men tinh toan; Ny, Qyp, Q, ^xp, ^yp, ^zp la lye dge, lye cat, mdmen tuong ung gay ung suit chay deo Hinh 3: Sff phan tir chiu tai Qua trinh lam viec cua vat lieu phan tir trai qua giai doan dien hinh (Hinh 4): * Vat lieu lam viec giai doan dan hdi * Vat lieu bit diu chay deo (dan deo) Tuygn tap bao cao Hgi nghj K H C N "30 nam Dau V i f t N a m : Cff hgi mdi, thach thde mdi" 21 Vat lieu chay deo hoan toan Hinh 4: Sff qua trinh lam viec ciia vat lieu phan tu • Md phdng cdc phdn tir cd khuyit tdt Cac phan tu cd khuyet tat dugc md hinh hoa de dam bao tinh chinh xac cua md hinh tinh Mdi khuyet tat dugc md ta bdi cac thdng sd:Vi tri khuyet tat, chieu sau va chieu dai vet niit Nd„ '^ybJ Hinh 5: Md hinh khuyet tat va phan bo irng suat Kha nang chay deo cua mdt phin tir ed khuyit tat thi hien qua cdng thuc: a]- s i1n a - - ^ ^nN-N, F i l - c o s ^ ^ ^7tN-N,^ ^^^^4-iiU ^-^^:^sma = M„ iV„ N, (1) Trong dd: MQ: Mdmen udn gay bien dang deo thuan No: Lye dge tryc gay biin dang deo nen thuan a: Ndp: arcos (1-Dd/R) C,^.a^ D.a{Ari'+t'-} 2r] r\: R{sina/a - cosa Cdp: 80.t/D Cac tinh toan tren dya vao cac gia thilt dh cap d tren, theo dd, tai mat cat di qua khuyet tat: - Bd qua khuyit tat vat lieu lam viec giai doan dan hdi, - Tinh vdi tilt dien thyc vat lieu bit diu chay deo, nghia la cd kl din khuyit tat 212 Mgt so kgt qua phan tieh danh gia lai kgt cau gian khoan bign co djnh phuc vu cdng tac khao sat Hinh 6: Sff bien chay deo cua phan tir bj khuyet tat Hesd RSR Xuit phat tu kha nang chju luc cua ket cau xac djnh theo bieu thuc: /?, R R{-^,-^)>F,-D + F,E F'F Trong dd: R: Kha nang chju luc cue ban cua ket cau Rs Kha nang chju lye cua ket cau (phi tuyen) RF Kha nang chju lyc eua cgc (phi tuyen) Gia trj tai trgng khdng phai la tai trgng mdi trudng D: Gia trj tai trgng mdi trudng E: He sd tai trgng khdng phai la tai trgng mdi trudng = 1,0 FD He sd tai trgng mdi trudng (phy thudc vao phan loai gian) FE He sd vat lieu ket eau =1,15 Fs He sd vat lieu nen - 1,0 FF (Gia trj cd the thay ddi theo yeu cau cua tung loai nen dat) Nhan ca hai ve vdi Fs va thay gia trj vao (2) ta cd: (2) R.,,r(Rs,-^) = \.\5.D + RSR*E (3) 1.13 Nhu vay, gia trj RSR la ty sd giira gia trj lyc ngang ldn nhat kit ciu syp va tai trgng mdi trudng vdi tan suat xuat hien 100 nam Gia trj cudng dy trir RSR tdi thilu phy thudc vao phan loai gian (theo API-RP-2A: vdi gian ed ngudi d, RSR > 1,6) Cac giai phap nham dam an toan cho ket cau De dam bao an toan eho ket cau, qua trinh tinh toan phan tich cac giai phap dua can phai dugc can nhac mdt each can than, chi tilt, ddng thdi phai tinh din tinh kha thi ciing nhu chi phi dau tu Cac giai phap dugc xem xet cd thi bao gdm: - Giam tai trgng tac dyng len ket cau: lam sach va cac sinh vat biin, thao bd cac ket cau thua, dd cac thiet bj khdng can thiet, v.v - Sua chira, gia cudng, bd sung lien ket nham tang cudng kha nang ehju lye cua eae lien ket (nut, phan tir, nen mdng, v.v ) tir dd nang cao kha nang chju lyc cua kit ciu Tuygn tap bao cao Hgi nghj KHCN "30 nam Dau Vift Nam: Co hgi moi, thach thde mdi' JAl CAC KET QUA THlTC HIEN XNLD VIETSOVPETRO Trong ndi dung bao cao nay, nhdm tac gia trinh bay ket qua phan tich danh gia lai cho gian khoan tai md Baeh Hd: gian dng dimg (RP) va gian cdng nghe trung tam CTP2 Cae tinh toan da duge co quan dang kiem Lloy'd Register chap nhan Dir lieu vao ciia PTDGL Dir lieu Thdng sd die lieu Chieu sau nude (muc nude tinh) (m) Hudng cdng trinh Dieu kien tugng, hai van Dia chat cdng trinh Hd so thiet ke Hd so hoan cdng Tieu chuan thiet ke Tieu chuan PTDGL Cac sd lieu khae (thay ddi tai trgng, v.v ) Hd so khao sat, bao gdm: an mdn, bam, cac khuyet tat, v.v ) Hd so bao tri, sira chii'a Du lieu thiet ke Sd lieu khao sat Sd lieu bao tri RP 49,5 x[3] x[3] x[3] x[3] x[3] BCH 51-3-83 AP1-RP-2A CTP2 49,4 x[4] x[4] x[4] x[4] x[4] BCH 51-3-83 API-RP-2A x[3] x[4] x[3] x[4] x[3] x[4] Kiem tra phan tich danh gia fl Kit qud phdn tich d mirc dp thiet ke Ket qua phan tich eho thay, nhieu phan tir, nhieu nut vugt qua iing suat cho phep, tudi thg mdi ciia nhieu nut ciing thap hom rat nhieu so vdi tudi thg mdi thiet ke Dudi day la bang tdng hgp cac ket qua tinh toan dien hinh: Trang thdi Chi tieu ddnh gid Dieu kien ben (USFmax)* Dieu kien dn djnh (USFmax) Dieu kien choc thung (USFmax) ULS FLS Ap luc thiiy tinh (USFmax) Sue chiu tai cua cgc chju nen (FOSmin)** Sire chju tai ciia cgc chiu keo (FOSmin) Do ben cua cgc (USFmax) Tudi thg mdi (nam) Ghi chu: RP Gia trj Gia tri tinh yeu cau 0,69 0,82 CTP2 Gia tri Gia tri yeu tinh cau < 1,00 < 1,00 < 1,00 1,18 1,69 4,65 1,50 2,80 > 1,50 134 > 1,50 0,91 50 0,36 >50 2,88 0,78 1,60 > 1,60 >1,60 >I,60 > 1,60 >I,60 >1,60 > 1,60 CTP2 Gia tri Gia tri tinh yeu cau 3,76 >1,60 • 10,37 >1,60 11,47 > 1,60 3,00 > 1,60 6,05 >1,60 11,50 > 1,60 15,00 > 1,60 11,03 >1,60 Ket qua phan tich ben gidi ban thay ca hai gian RP va CTP2 diu cd RSR > 1,6, dd cd the ket luan: gian RP va CTP2 van dam bao kha nang ehju luc Tuy nhien, de tang cudng kha nang chju lye cua hai gian tren, nhdm tac gia da dl mdt sd bien phap giam tai cho gian nay, tham khao [3, 4], dd: - Yeu cau tien hanh sua chua, gia cudng cac phan tu bj hu hdng nhu da trinh bay hd so khao sat, d^e biet la cac phan tu chinh (cae phin tu ehju lye tren kit eiu chan de, cac phan tu cd he sd sir dyng ldm) - Su dyng khdi be tdng mac cao de gia cudng cho bdn nut dudi cimg cua khdi chan de gian RP - Danh sach va cac sinh vat bien bam tren kit eiu chju lyc d vung tir 4m din 12m de giam tai trgng sdng va ddng chay - Tang cudng cdng tac khao sat chi tilt cho cac nut cd tudi thg mdi thip dh kjp thdi phat hien cac vet nut va tde phat triln cua chiing KET LUAN VA KIEN NGHI Dl edng tac PTDGL phye vu eho tu bao dudng kit eiu chju lye gian khoan biin dat kit qua tot, sd lieu diu vao phye vy PTDGL phai diy du va ed tin cay cao Tren thyc tl cac gian khoan biin co djnh trudc day Lien Xd cu thilt kl, dd: _^ - Tat ca cac gian diu dugc thilt kl theo dang djnh hinh hda, hd so thilt kl khdng day du, hd so hoan cdng cac cdng trinh cdn thilu, dac biet la so lieu tai trgng cae thilt bj, edng nghe thugng ting, ehilu sau ddng ege, v.v - Vj tri cac nut khao sat, dac biet la cac nut thude chan dk ein phai dya tren co sd cae bao cao tinh toan, phan tich danh gia lai kit eiu chju lyc (Trong cae bao cao cd ehi thdi gian'va vj tri cac nut ein phai khao sat) - Can cd nghien cuu de xay dyng he sd giam tai tai trgng mdi trudng PTDGL phu hgp vdi dieu kien biin Viet Nam (vi dy: Tieu chuin API cho phep liy bing 85% hoae 50% tai trgng mdi trudng eye ban 100 nam ddi vdi gian cd hoae khdng cd ngudi d PTDGL - •vning vjnh Mebico) Tuyin tap bao eao Hdi nghj KHCN "30 nam Dau Vift Nam: Co h5i'^-°'' thach thde mdi" 217 - Cac sd lieu dja chat tai vj tri xay dyng cac edng trinh biin eua X*i^NG chu yeu dugc thyc hien theo tieu chuan Lien Xd cii, cac sd lieu da lac'iiep diu phu hgp vdi cac tien bd khoa hgc - ky thuat tinh toan phan tieh hien nay, Hydrate lam viec ddng thdi giira cdng trinh vdi dit nIn (hien cac so lieu dang dugc sir utay cho PTDGL la cac sd lieu chuyen ddi tuong duong theo quan dilm chu quan cua hang John Brown, khdng dam bao tin cay) Quy trinh PTDGL neu tren la phu hgp cac tieu chuin quy pham thi gidi va phu hgp vdi nang lyc tinh toan phan tich cua XNLD Vietsovpetro Tuy nhien, qua trinh ap dyng cdn gap rat nhilu khd khan mdt sd tieu chi danh gia chua duge xac djnh cy thi phu hgp vdi dilu kien bien Viet Nam va yeu ciu eua co quan dang kilm qudc tl Do vay, can cd nhumg nghien ciiu cy thi dl xay dung quy pham eho dilu kien biin Viet Nam Cac PTDGL can tuan thu theo quy trinh da xac lap, nhien cung ein xem xet cu thi timg trudng hgp PTDGL kit ciu dl cd cac kit luan, danh gia dung din tren co sd cae ehi tieu so sanh cua trang thai gidi han neu tren PTDGL la cdng viec cap thiet can cd sy quan tam dung muc, cac yeu eiu sau PTDGL can duge tuan thu nghiem ngat dam bao cho sy an toan cua cae cdng trinh biin qua trinh khai thac, su dyng, dac biet la cdng tae khao sat, tu, bao dudng Cdng tac PTDGL la rat khd khan, phue tap, cin cd su quan tam diu tu thich dang cho viec xay dyng dgi ngu PTDGL thdng qua viee dao tao, giao luu hgc hdi vdi cac edng ty, chuyen gia cd nhieu kinh nghiem tren thi gidi Can luu y den cac kien nghj, yeu cau cua co quan dang kilm cu thi: - Can xem xet lai he thdng chdng an mdn cua cae gian hien dang boat dgng - Can xem xet, chinh xac hda sd lieu dja chit va cac so lieu diu vao phuc vu cho viec PTDGL TAI LIEU THAM KHAO Recommend practice for fixed offshore structure (API-RP2A) Dd Som, Lam Quang Chiln, Hoang Le Ngoc Vinh, Vu Xuan Lai, 2000 Quy trinh phdn tich, ddnh gid lgi trgng thdi ky thudt cdc kit cdu cong trinh ddu biin Hgi nghi Khoa hgc - Cdng nghe 2000 ''Ngdnh Ddu trudc thim thi ky 21", NXB Thanh nien, tr 324 - 329 Riser platform (RB-CTP2) jacket and topside re-analysis report, Vol 1, & CTP-2 platform re-analysis report, Vol & SESAM theory manual USFOS - Det Norske Veritas Cac de tai khoa hgc ciia phdng NCKH va TK, XNLD Vietsovpetro tir nam 2001 2004 ... phi tuyen ket cau chju lye bang each tang tai trgng timg muc, din tdi sy lam viec cua ket cau d mien phi tuyen (ke den ea phi tuyen hinh bgc va phi tuyen vat lieu), qua trinh tai mdt sd phan tu. .. ket cau edng trinh bien cua XNLD Vietsovpetro • Vdt lieu ldm viec giai dogn ddn deo Xet phan tu ehju tai trgng (Hinh 3), phuomg trinh mat dan deo cua vat lieu phin tu: r=/ N_ N Q, M, M^ ^yP M,... hanh sua chua, gia cudng cac phan tu bj hu hdng nhu da trinh bay hd so khao sat, d^e biet la cac phan tu chinh (cae phin tu ehju lye tren kit eiu chan de, cac phan tu cd he sd sir dyng ldm) - Su