Tuygn tap bao cdo HQi nghj KHCN "30 nam Dau khi Vigt Nam Cff hdi mdi, thach thuc mdi" 947 HOAN THIEN PHU ONG PHAP DÛ BAO AP SUAT GILTA CAC COT ONG CHONG (GOC) O CAC GIENG KHAI THAC D A U CUA XNLD VIE[.]
Tuygn tap bao cdo HQi nghj KHCN "30 nam Dau Vigt Nam: Cff hdi mdi, thach thuc mdi" 947_ HOAN THIEN PHU-ONG PHAP DU^ BAO AP SUAT GILTA CAC COT ONG CHONG (GOC) O CAC GIENG KHAI THAC D A U CUA XNLD VIETSOVPETRO Nguyen HQu Chinh, Vo Thanh, Duong Van Son XNLD Vietsovpetro TOM T A T r y w r Hiin tugng cd dp sudt cao tdn tgi liin tuc trin mieng giing khoan giira cdc cdt dng chdng (GOC) Id vdn di phiin toai dang duge theo ddi chat che & XNLD Vietsovpetro Hiin tugng ndy chimg td ed du&ng ddn ngudn ndng lugng Id hodc chdt ldng xdm nhdp vdo khdng gian vanh xuyin GOC & mieng giing khoan Bin cgnh cdng tdc ngdn ngira dp sudt GOC da dugc triin khai tir ndm 1997 bdng cdc chuong trinh hodn thien cdng nghi gia cd vd xdy dung giing khoan, XNLD Vietsovpetro vdn quan tdm dge biit din cdng tdc khdc phuc chung & cdc giing dang khai thac Di cdng tdc ndy cd hiiu qud thi viec du bdo dp sudt GOC cd vai trd vd cung quan trgng Du bdo dp sudt GOC Id xdc dinh ngudn gdc vd mirc nguy hiim, tir dd xdc dinh dugc phuong phdp phii hgp nhdt khdc phuc hodc gidm b&t muc nguy hiim Trong bdo cdo ndy cdc tdc gid trinh bdy mot phdn kit qud nghiin cim ly thuyit vd thuc nghiim ciia cdc chuyin gia Viin NCKH vd TK Ddu biin vd cdc dem vi thdnh viin cua XNLD Vietsovpetro nhdm hodn thiin phuong phdp du bdo dp sudt GOC di dp dung cho cdc giing khai thde dang hogt ddng cua XNLD Vietsovpetro MODAU Sir phat minh xi mang pooelang cua Joseph Aspdin da tao buoc tien bo co ban nen van minh ciia chiing ta vi gia re, ciing va kha nang dong ran nuoc Xi mang pooelang dugc sir dung Nganh Dau tu dau the ky XX va hien van dugc coi la phuong tien chinh de lam kin khoang kh6ng gian giQa gieng khoan va cot 6ng ch6ng (hay giQa cac cot 6ng ch6ng) [5] Qua trinh tram xi mang gieng khoan chinh la nham tao vanh da xi mang day Do kin ciia vanh da xi mang la mpt nhQng th6ng s6 quan trgng ve chat lugng xay dung gieng khoan Yeu cau ve dieu la cac san pham via long dat kh6ng tham va khong ro ri qua kh6ng gian vanh xuyen da tram xi mang su6t thai gian khai thac Noi chung, sau tram xi mang va dua gieng vao khai thae, kin thuong dat yeu cau Tuy vay, de dam bao an toan va kiem soat boat dong ciia gieng khai thac dau nhu mot c6ng trinh xay dung nhan tao long dat, theo qui dinh bat buoc phai each ly khoang kh6ng gian vanh xuyen tren mieng gieng khoan giQa cac cot 6ng eh6ng (GOC) bang t6 hgp thiet bi dau gieng M6i khoang kh6ng vanh xuyen deu gan d6ng h6 chi bao ap suat Theo ly thuyet, ap suit a day phai la Trong tnrong hgp d6ng hi chi ap suit bao hieu khae chiing to gieng eo ap suit giQa cac cot ong ch6ng va bat buoc phai dugc theo doi chat che Nguyen nhan co thi thay dii nhiet hoae su ro ri rit nho kh6ng lien tuc Trong truong hgp ap suat se kh6ng cao va khong gay nguy hiim Nlu nguyen nhan 948 Hoan thien phuong phap du bao ap suht giQ-a cac cdt dng chong (GOC) ff cac gigng khoan ximang hu hong, chua each ly dugc cac via nong, diu gilng kh6ng kin, cot cin khai thac, Ing ching packer bi ho, v.v thi ap suat GOC se tin tai lien tuc co thi dat toi gia tri rat cao, gay nguy hiem cho nguoi va m6i truong Truoc ap dung cae bien phap loai tru hoae giam bot miic nguy hiem ciia hien tugng ap suit cao GOC a m6i gieng khoan can phai tiln hanh c6ng tac du bao chiing Du bao ap suit GOC la xac dinh ngu6n goc va muc nguy hiim, tu dl phuong phap phu hgp nhit khae phuc hoae giam bot miic nguy hiem Cac phuong phap du bao deu da dugc trinh bay cae tai lieu [4, 5,6] Tuy vay, kh6ng phai truong hgp nao cung co the ap dung dugc ma phai can cii vao dieu kien ky thuat - dia chat cu the ciia tung gieng hoae nhom gieng tren cac vung mo kbac Hon nua, can phai c6 phuong phap xu ly phii hgp cac so lieu de co the thu dugc nhiing thong tin day dii nhat ve tinh chat tham dan luu chat khong gian vanh xuyen TONG QUAN VE TRANG THAI AP SUAT GILTA CAC COT ONG CHONG, CONG TAC Dir BAO VA N H I T N G VAN DE TON TAI XNLD Vietsovpetro co 250 gieng khoan thi 56%o (140/250) s6 gieng ghi nhan co ap suit GOC [3] Phan b l ty le nhu sau (Hinh 1): - Ap suit GOC kich thuoc 6" (7") va 9" (P6 x 9) = 44,8% (112/250); - Ap suit GOC 9" va 12" (P9 x 12) = 34,0% (85/250); - Ap suit GOC 12" va 16" (P12x 16)= 11,6% (29/250) Trong sl 140 gilng co ap suit GOC: P6(7) x = 80%(112/140); P9 x 12 = 60,7% (85/140); P12 x 16 = 20,7% (29/140) Ty le theo cac gilng khai thac dang boat dong: P6(7) X = 52,3% (91/174); P9 x 12 = 39,7% (69/174); P12 x 16 =14,9% (26/174) 90 80 70 60.7 60 52 ^ 50 ^ 44 B %treii tong s6 gi^g khoan (GK) • %tren tong so GK co ap suit GCO • %trai tong s6 GK khai thac 3««.e w 40 30 -I 20 10 P6(7)x9 (Khai thac) P9x12 (Ky thuat-2) P12x16 (Ky thu§t-1) Kfch thoot (loai) vanh xnyen giaa cat cot ong cbSng Hinh 1: Bilu tv le so GK co ap suat GOC Tuygn tap bao cao Hgi nghj KHCN "30 nam Phu Vigt Nam: Cff hdi mdi, thach I uc mdi' 949 P6(7) X 9, P9 xl2, P12 x 16 a cac gilng khai thac dang boat dong (Hinh 2): P6(7) x < l,OMPa: 19^8% (18/91); l,OMPa < P6(7) x < 3,0MPa: 24,2% (22/91); 3,0MPa < P6(7) X < 6,0MPa: 34,0% (31/91); 6,0MPa < P6(7) x 9: 22,0% (20/91); P9 x 12 < l,OMPa: 49,3% (34/69); l,OMPa < P9 x 12 < 3,0MPa: 31,9% (22/69); 3,0MPa < P9 x 12 < 6,0MPa: 18,8% (13/69); P12 x 16 < l,OMPa: 72,1% (19/26); l,OMPa < P12 x 16 < 3,0MPa: 26,9% (7/26) 80 -, m P GOC 6(7)x9 • P GOC 9x12 • P GOC 12x16 22 PGOC8.0 MPa Hinh 2: Bieu ty le so GK co ap suat GOC theo gia tri ap suat • Nhirng van de ton tai cong tac dy bao Vao thang 5-1989 lin diu tien ap suit giQa cac cot ong ch6ng duge ghi nhan va dua vao bao cao chinh thtic hang Tuy vay, chi ap suat GOC nhan thay nhieu gieng khoan voi gia tri cao hon 7,0MPa thi vin dl moi chinh thiic dugc dua thao luan va nghien cuu tim bien phap ngan ngua va khic phuc (3-1994) XNLD Vietsovpetro da phe duyet chuong trinh gIm 16 muc tu thilt kl gilng khoan, ch6ng Ing, tram xi mang, loai vat lieu, quy trinh thu kin Ing ching, thilt bi diu gilng, goi dong, dua gilng vao khai thac, sua ehua Ion gilng khoan, v.v nhim muc dich nang cao chat lugng xay dung gieng khoan de ngan ngua sir xuat hien ap suat GOC D6i voi cac gilng da co ap suit GOC, c6ng tac nghien cuu, du bao thuang la xac dinh nguIn ap suat bang each kilm tra thiet bi mieng gieng, phan tich mau khi, tim moi lien he giua ap suat GOC voi ap suit ngoai ein doi voi gieng khai thac tu phun va gaslift [1, 2] Phuang phap xa ap suat va theo doi su khoi phuc ciing dugc ap dung Tuy nhien chiing chua dugc chuan boa, da bi bo qua nhieu thong s6 nen cac th6ng tin thu dugc ehua dii dl danh gia tinh trang ap suit GOC a mli gilng Truoc tinh hinh do, Cong ty 3Kc5yp K° cua Cong hoa lien bang Nga da tien hanh du bao va kbac phuc ap suat GOC tai gieng Phuong phap su dung dugc lay tu mot so viing 950 Hoan thien phuong phap du' bao ap suht giua cac cdt dng chdng (GOC) d cac gieng khoan mo dac thu ciia CHLB Nga va da cho nhung ket qua thuyit phuc ban Tuy nhien Iu6n lu6n t6n tai nhiing diem chua khae phuc dugc de ap dung triet dl cac phuang phap da dugc chuan hoa CHLB Nga De du bao ap suat GOC, nguoi ta co the tan dung nhiing s l lieu tu nhilu nguon khae Thuan lgi va tiet kiem nhat thi phan Ion cac s6 lieu la thu dugc tu sir kiem soat qua trinh khoan va khai thac th6ng thuang Chi co the sii dung de h i trg gian tiep them th6ng tin de phan tich, danh gia ap suat GOC Mot s6 phuang phap hien dai khae ap dung deu can phai ngung qua trinh khai thac (do chat lugng xi mang tinh trang ky thuat cot 6ng ch6ng, miic chat long gieng, v.v.) Phuong phap nghien ciiu kh6ng gian vanh xuyen bang each xa va cha kh6i phuc ap suat GOC deu dugc cac chuyen gia ciia My va CHLB Nga su dung [4, 5, 6] Day la phuong phap nhat true tiep tac dong vao d6i tugng nghien ciin ma kh6ng can ngung qua trinh khai thac gieng dang lam viec Qua trinh xa ap suat tu khong gian vanh xuyen la ca hoi tot nhat de thu dugc thong tin ve the tich khoang khong (mu khi), phan va kha nang dong chay a cac kenh dan hoae vi kenh dan Th6ng thuang, viec luu lugng va the tich khi xa bing phuong phap djnh ca, nghia la cho dong chay qua nhung 16 nho da biet kich thuoc Day la phuong phap tinh gan diing toe xa va the tich Trong qua trinh xa cin ghi lai s6 lieu ap suat tren can khai thac, ap suat ngoai can va tren tat ca cac cot Ing ching khae de CO day dii th6ng tin ve su lien he giua chiing Cac chuyen gia Nga chii xay dung duong cong giam ap suit va giam luu lugng qua trinh xa de danh gia kh6ng gian vanh xuyen Tuy vay, cae gilng da dugc ap dung deu nam tren dat lien co qua trinh khoan, gia c6 gilng voi cae dilu kien va yeu clu hoan toan khae Co quan quan ly tai nguyen ciia Hoa Ky cung yeu clu phai kilm tra thai ky kh6i phuc ap suat T6e khoi phuc ap suat cung d p th6ng tin vl kich thuoc va vi tri c6 thi ro ri ciia luu chat Tuy nhien, cac chuyen gia Hoa Ky chua xii ly dugc sl lieu kh6i phuc ap suit [6] Cung nhu qua trinh xa, kh6i phuc ap suit cin ghi lai diy du sl lieu ap suat khai thac va tren cac cot 6ng ch6ng khae DAC DIEM PHU^ONG PHAP DU BAO AP SUAT GOC XNLD VIETSOVPETRO Ben canh viee thu thap cae th6ng tin diy dii nhit vl dia chit, dia vat ly, vl gia cl gieng, lich sii qua trinh khai thac, sua chua gilng co lien quan hoae tae dong din vanh xi mang, chiing t6i dac biet chii y den viee nghien ciin thiiy dong luc hoc khong gian vanh xuyen co ap suat GOC Day chinh la c6ng tac hoan thien qua trinh xa va kh6i phuc ap suat da dugc ap dung tren the gioi Cach xac dinh luu lugng va the tich khi xa ap suit tu kh6ng gian vanh xuyin qua 16 nho dinh co co ban che la khong dieu khien dugc qua trinh xa, co thi tin rit nhilu thai gian lugng Ion, ket qua thu dugc la gian tilp tinh toan qua dai lugng thai gian Do vay chiing t6i da xac dinh the tich xa va dieu khiln tie xa bing dung cu luu lugng co nguyen tae boat dong kieu quay tuoc bin, ma hieu ArAT-1-50 Bing dung Tuygn tap bao cao Hdi nghj KHCN "30 nam Dau Vict Nam: Co hdi mdi, thach thiic mdi" 951 eu nay, bit cii thai dilm nao co the doc dugc luu lugng tiic thai va the tich da di qua day, chiing t6i chii viec xii ly s6 lieu thu dugc ap suat kh6i phuc, xay dung duong cong khoi phuc ap suat theo ham s6 thai gian: P = f(T)(l) Lap m6 hinh va xay dung m6i lien he t6c dong cung cap vao kh6ng gian vanh xuyen theo ham s6 thai gian va ap suat kh6i phuc theo phuong trinh: dV/dt = f(T) (2) dV/dt = f(P) (3) M6 hinh duge lap nhu sau: Gia sii khoang kh6ng gian tu chua a mieng gieng CO the tich VQ Ta xet khoang kh6ng a trang thai la (n-1) voi Vn-i Pn-i va (n) voi Vn, Pn (Hinh 3) Do vi tri ciia khoang kh6ng nam quanh khu vuc dau gieng va thoi gian la qua trinh kh6i phuc nen nhiet o trang thai co the coi nhu khong d6i Ta co the sii dung dinh luat B6i-Mari6t ap suat dang kh6i phuc tu trang thai (n-1) den trang thai (n) Sir kh6i phuc ap suat la co mot lugng (AVpn ) xam nhap vao khoang kh6ng gian tu tren mieng gieng Trang thai (n-1) Trang thai (n) Hinh 3: Mo hinh tinh luu luong khoi phuc Hien nhien: VQ = Vn-i = Vp + AVpn Theo dinh luat B6i-Mari6t: PV = const, ta co : P V Pn-lVp., = PnV„ P V p AVpn = V,.,-Vn = V , (5) = V,.,(1- pn-\ P AP ) = Vc ) = N„.,{ — p P (^.+1) _ AVp,(Pd+l) Trong do: Pj - Gia tri ap suat dugc qua trinh kh6i phuc, kg/cnr dV - AV(p=,kg/cni (4) (6) TIEN HANH THtT NGHIEM PHUONG PHAP DU BAO AP SUAT GOC Phuong phap du bao ap suat GOC voi nhQng dac diem tren day da duge thu nghiem nam 2004 tai cac gieng khoan cua XNLD Vietsovpetro, cac ket qua thu dugc eho thiy ring: Phan tich duong cong kh6i phuc ap suat: th6ng thuong, sau xa ap suit 952 Hoin thien phuong phap dy bao ip suat giQ'a cac cdt dng chdng (GOC) d cac gieng khoan kh6ng gian vanh xuyen ve 0, dong van xa va theo doi su kh6i phuc ap suat Sau do, xay dung d l thi gia tri ap suit theo thoi gian, chuyen gia tri thai gian thang Logarit (Hinh 4) Tren co so co the phan loai (4 dang) cac duong cong kh6i phuc ap suat [4] 90-1 SO- TO - s 60-1 a KVD-14 KVD-9 KVD-6x9-11 KVD-6x9-81 KVD-6x9-80 KVD-6x9-91 KVD-12 KVD-100 KVD-9X12-11 KVD-9X12-81 -»-KVD-9x 12-80 KVD-9x12-91 • < 40 4.5 Hinh 4: Do thi khoi phuc ap suat 0.06 '§ 0.05 I 0.04 - ^ dV/dt-14 * dV/dt-100 dV/dt-12 0.03 — dV/dt-9 0.02 0.01 - '»' 'W 'W.si W S-W^fflSHfrffi » • • - - , -.^w^.ifr.NW„ ,^„ Ki u^ SCO ITOO 1500 2000 Thoi gian, phut Hinh 5: Do thi dV/dt theo thoi gian 1500 Tuyen tap bao cao HQi nghj KHCN "30 n i m DSu Viet Nam: Cff hdi mdi, thach t h u c mdi" 953 0.06 ãằ-dY/dt-14 ô"dV/dl-100 dV/dl-12 dV/dt-9 10 20 40 Ap suat, i