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536 Trudng ung suSt hien tai va ap suit thanh he trong hi Ciiu Long va Nam Con Son, TRlTCJNG ITNG SUAT HIEN TAI VA AP SUAT THANH HE TRONG BE CUtJ LONG VA NAM CON SOOV, THEM LUC DIA VIET NAM Nguyin Thi[.]
536 Trudng ung suSt hien tai va ap suit he hi Ciiu Long va Nam Con Son, TRlTCJNG ITNG SUAT HIEN TAI VA AP SUAT THANH HE TRONG BE CUtJ LONG VA NAM CON SOOV, THEM LUC DIA VIET NAM Nguyin Thi Thanh Binh Tomochika Tokunaga Trw&ng Dai hoc Tdng hgp Tokyo Hoang Phuac Son, Mai Van Binh XNLD Vietsovpetro N126_V(40) TOM TAT Di thiit ki cdc giing khoan cd lech l&n, md td dge diim tdng da chua, cung nhu nghien ciru dia ddng luc vd cdc dnh hu&ng ciia chiing din suphat triin ciia bi trdm tich thi hieu tru&ng img sudt tgi chd la diiu cdn thiet Su dung tdi lieu thu dugc cdng tdc thdm dd vd khai thde ddu khi, cdc tdc gid da tiin hdnh phdn tich trucmg img sudt tgi chd vd dp sudt thdnh hi ciia mdng tru&c Di tam vd cdc tdng phii bi Ciru Long vd Nam Cdn Son & thim luc dia Nam Viet Nam Hu&ng ciia ung sudt ngang cire tiiu vd cue dgi dugc xdc dinh theo hu&ng sap l& thdnh gieng khoan vd hu&ng cua khe nut sinh qud trinh khoan O bi Cu'u Long, img sudt ngang cue dgi cd hucmg tir Bde Tdy Bde - Nam Ddng Nam din Bde - Nam &phdn phia Bde vd khdi ndng Trung tdm, tu Ddng Tdy din Tdy Bde - Ddng Nam phdn phia Nam O bi Nam Cdn Son, irng sudt ngang cue dgi cd hu&ng theo Ddng Bde - Tdy Nam a phdn Bde vd Bde Nam & phdn Trung tdm Cu&ng cua img sudt thdng dung (hay img sudt doc) dugc xdc dinh tir tdi lieu •:arota mat ung sudt ngang cue tiiu dugc xdc dinh tir tdi lieu thir va via cd chdt lucmg tdt lfng sudt ngang cue dgi dugc tinh tu phucmg trinh nirt via thuy luc Chi ung sudt hiin tgi & be Ciru Long ed thi dugc xem la chi tgo dirt gdy thudn, & bi Nam Cdn Son tdn tgi cd chi tgo dut gdy thudn vd dirt gdy trugt ngang Anh hu&ng ciia su thay ddi dp sudt thdnh hi lin cuong truong ung sudt tgi chd da dugc phdn tich dua tren tdi lieu tir cdc vung cd dp sudt thdnh he suy gidm vd dp sudt cao Sudung cdc phucmg trinh thuc nghiem thu duge, cdc tdc gid cd thi md td hgp ly trucmg irng sudt tgi chd vd dp sudt thdnh hi cua vung nghien ciru MO DAU Viec nghien cim ung suat tai ch6 ciia Trai dat da thu hut dugc su quan tam ciia cac nha khoa hoc dia chat tren thi gioi iTng suit hien tai dugc sir dung rong rai boi cac co so nghien cim va cac co so san xuit c6ng nghiep nhilu ITnh vuc ve khoa hoc trai dat nhu dia dong lire, khai thac dau va c6ng trinh 537 Tuygn tap bao cao HQi nghj KHCN "30 nam Phu Viet Nam: Co' hoi mdi, thach thiic mdi" Viet Nam, mgt s6 nha nghien cim vl kiln tao nhu Borisov (1996) Schmidt va n.n.k (2003), Cao Dinh Trilu va Mai Xuan Bach (2004) da tiln hanh nghien cim c6 kiln tao va huong img suit c6 Tuy nhien, huong va cuong truong img suit tai ch6 be trim tich cua Viet Nam van chua dugc hilu ro Trong bai bao nay, cac tac gia phan tich huong va Ion truang img suit tai ch6 tren co so tai lieu dia vat ly gieng khoan va ket qua thir via cac gilng tham va khai thac a be Cim Long va Nam C6n Son Cac tac gia cGng phan tich anh huong ciia di thuong ap suat len che iing suat tren co so khai niem ciia ly thuyet r6ng dan h6i DAC TRU^NG DIA CHAT CUA BE CUtJ LONG VA NAM CON SON L Dac diem chung cua be Ciru Long Be Cim Long la be tram tich De tam nam o phia D6ng Nam them luc dia Nam Viet Nam (Hinh 1) CO dien tich khoang 250km x 100km Day la vimg khai thac dau chinh ciia Viet Nam 106°E 108**E 10**N 10'^N 8°M 8°U lOe^E 108°'E Hinh 1: Ban vi tri be Ciru Long va Nam Con Son B I Ciru Long la be tach gian theo huong D6ng BIC - Tay Nam, dugc tao boi qua trinh tao rift vao Oligocen som (Nguyin Du Hung va Le Van Hung, 2003) Trong bl co thi 538 Tru-6-ng irng suat hifn tai va dp suat th^nh hf bg Ciru Long v^ Nam Cdn jojiy dugc chia ba khu vuc lang dgng tram tich va nhilu clu tao Cac khu vuc ling dgng trim tich nim phan Bae, Tay va Dong cua be Cac lofp phii tram tich co tuoi thay doi tir Eoxen (?) din De tii va chilu day Ion nhat khoang 8km (Vo Nang Lac va n.n.k., 1997, Phan Truong Thi va n.n.k., 2003) Trong giai doan dau ciia pha tach gian, cac dia hao hep dugc tao va mgt qua trinh oIn vong tao nen mot be liin chim n6ng True cua be lai bi liin chim nhanh vao Oligocen mugn Vao cuoi Miocen som bien tien phu rong toan dien tich be, cac tang set day Rotalia dugc tich tu, chiing la tang chan khu vuc Cac tang tram tich Miocen giiia - Miocen tren va Pliocen - De tii dugc lang dgng cac chu ky bien tien, bien thoai cua chau th6 Cim Long hien dai Cac chu ky bien tien, thoai hi anh huong boi sir thay d6i ciia mirc nuoc bien Cot dia ting tong hgp cua be Cim Long dugc trinh bay Hinh UthoK^y t^positlonal Env f Sandstones interbsdeted with minor Smestone Ato^omiles RotaUte shale Sandstones irtefiieskieti vtiXh Oaystones Minor coals Shadow marine SarHJstones snd ciaystanes •; Barh Ho shale Coaslal (rfairt sanetetones ctaystones inteftiEidded Lacustrine shale Sdluviat sandstones A^ose sandstones/ claystor»s hTtert»eddeel volcanlc^ntrusive dyke DeftaicShaHoM marine LacusirlneRuvial Delt»c Ffesh water UacusltirtB/ AHuviat fan e S I Grante^^nodiorite Pre-ntt Faulting vtiic antes Hinh 2: Cot dia tang bi Cu-u Long (theo Nguyin Du Hung vd Le Vdn Hiing, 2003) Tuygn tap Mo cao Hoi nghj KHCN "30 n^m Dau Vift Nam: Cff hoi mdi, thach thuc mdi" 539 Dac diem chung cua bi Nam Con Son Be Nam Con Son ciing la mgt be tram tich De tam nam phia D6ng Nam thim luc dia Nam va nim gin kl bl Cim Long (Hinh 1) B I CO dien tich khoang 90.000 km^ cung la mot viing khai thac diu va chinh cua Viet Nam Be nam or noi giao cua hai he th6ng kiln tao chinh gin voi sir tach ciia mang D6ng Duong va tach gian day Biin D6ng Bl co huong D6ng BIC - Tay Nam phin phia Bae va Nam - D6ng Nam a phin phia Nam ciia bl Trong bl co hai triing lun noi ling dgng tram tich chinh va nhilu clu tao Cac trung liin ling dgng trim tich nim phia BIC va Trung tam cua be Cac lop phu trim tich co tu6i tir Oligocen din De tir va c6 chilu day Ion nhit khoang 10km (Hoang Ngge Dang, 2002) Trong giai doan Eoxen - Oligocen, tach gian gin vai hinh Biin D6ng tao cac ban dia hao co huong D6ng BIC - Tay Nam va cac tao tram tich hinh boat dgng tao rift, lip diy cac ban dia hao Khi qua trinh liin chim tilp tuc, cac ban dia hao rieng biet da dugc lip diy, trim tich tra nen mang tinh khu vuc ban, tram tich tuong s6ng tich tu rong khIp tir huong Tay cua bl chung co ty le chilu day hieu dung so voi chilu day chung Ion Cac tap hgp trim tich o khu vuc sut lun co tuong thay d6i tir luc dja den biin tir duoi len tren, tuong biin kha ph6 biin tir Tay sang D6ng qua trinh biin tiln va thu hep d6ng bing chau th6 vao Miocen som Vao cuoi Miocen giira, su mo rong theo huong Tay BIC - Dong Nam gin vdi sir thay doi huong tach gian cua day Biin Dong lam thay doi dia hinh Trung tam b6n trung chung anh huong din clu tnic ciia cac tuong tram tich, trim tich carbonat phat triln ban chi a phin thim va chan thim phin thim sau tudng suon d6c dugc tich tu cac dia hao Vao Miocen mugn, bl dugc tai boat dgng kiln tao bori sir nghich dao nhe, tilp theo sir lun chim, din din tao cac clu triic ldn da v6i am tieu va cat tudng dong chay roi Qua trinh hi gian doan vao Pliocen sdm qua trinh biin tiln Cot dia ting tdng hgp cua bl Nam C6n Son dugc trinh bay Hinh 540 Tnrdng irng suat hien tai va ap suat he bi CUTI Long va Nam Cdnjg}^: Hinh 3: Cot dia ting bi Nam Con Son (theo Hodng Ngoc Dang 2003) Tuygn tap bao cao HQi nghj KHCN "30 nam Phu Viet Nam: Cff hoi mdi, thach thiic mdi" 54]^ HUONG ITNG SUAT TAI CHO TRONG BE ClTU LONG VA NAM CON SON Tai lieu sir dung xac djnh trircmg u'ng suat tai cho Cac tac gia tiln hanh phan tich trudng ung suat tai ch6 va ap suat he vimg nghien cim dua tren tai lieu dia vat ly gieng khoan, thir via, nirt via thiiy luc va phan lich mau loi Mgt so tai lieu dugc T6ng cong ty Dau Viet Nam va Vien Dau Khi cho phep tham khao Mgt phan khae dugc thu thap tir cac ngu6n khae nhu cac bao cao va tai lieu da xuat ban (Martyntsiv va n.n.k., 1996; Sirin-dade va Duong Danh Lam, 1996; Pham Hong Que, 1996, Korolev va n.n.k., 1997, Schmidt va n.n.k., 2003, Hoang Ngoc Dang va Mai Thanh Tan, 2000, Hoang Ngge Dang, 2002, Nguyen Dinh Ha, 2003, Mai Van Binh va nn k., 2004) va cac luan an tien sT (Hoang Ngge Dang, 2002 va Nguyen Dinh Ha, 2004) Hu'dng irng suat tai cho Hudng sap Id gieng khoan va hudng nirt ne sinh qua trinh khoan d gieng khoan cho hinh anh ro net ve hudng cua iing suat (Brudy va Zoback, 1999) Trong gieng khoan thang dung, true sap Id cho biet hudng ciia img suat ngang cue tieu khe niit tao khoan c6 hudng triing vdi hudng cua iing suat ngang cue dai De tranh anh hudng bao mon gieng khoan dugc sinh choong khoan d cac gieng khoan nghieng, cac tac gia chi sir dung tai lieu tir cac gieng khoan goc nghieng nh6 ban 20 Hudng sap Id gieng khoan cd the xac dinh bang tai lieu chup anh gieng khoan nhu: BHTV, CAST-V (Hinh 4) hoae FMI va cac s6 dudng kinh gieng khoan Chat lugng tai lieu dimg de phan tich dat chat lugng A va B theo tieu chuan chat lugng ciia du an nghien ciiu trudng img suat hien tai cua the gidi (Zoback, 1992) D6i vdi loai CO chat lugng hang A, mgt gieng co lech nho hon 12 phai quan sat ro mudi hay hon mudi khoang sap Id gieng klioan vdi t6ng chieu dai sap Id hon 300m D6i vdi loai CO chat lugng hang B, mot gieng khoan co lech nh6 hon 20 phai quan sat dugc ro rang it nhat khoang sap Id vdi t6ng chieu dai hon 100m 542 TruoTig ling suat hien tai va ap suat he bg Ciiu Long v^ Nam Con Son, a) 360 i^ ( ^ ' ' ;^^ i ; ' -• I : kl: -I n (t i ' , ,, b) 'jflSjja^KMKftSB-*^ ••jff&Jft Nut ne tao qua trinh khoan theo huong Dong Bae - Tay Nam Hinh 4: Vi du ve xac djnh hirang sap 16" gieng khoan (a) va hu-otig nut ne tao qua trinh khoan theo tai lieu CAST-V (b) O be Cim Long, sap Id va khe niit sinh qua trinh khoan quan sat dugc Miocen dudi (he tang Bach H6) va mong niit ne d gilng khoan d be Nam C6n Son, sap Id va khe nurt sinh qua trinh khoan dugc quan sat d gilng khoan thuge cac tang Tuygn tap bao cao Hoi nghj KHCN "30 nam Phu Viet Nam: Cff hoi moi, thach thuc mdi^ 543 Miocen giua, Miocen dudi, Oligocen va mong nirt ne Du: lieu dia vat ly gieng khoan CAST-V va FMI tir gilng khoan viing nghien cim cho thiy kh6ng co thay d6i mot each he thong hudng iing suat theo sau H I U hit khe nirt sinh qua trinh khoan co hudng song song vdi true gieng khoan, dilu chiing t6 ring img suit thang dimg la mgt nhir ng iing suat chinh Ci bl Cim Long, img suit ngang cue dai, ve co ban c6 hudng Bae Tay Bae - Nam D6ng Nam din BIC - Nam phin phia Bae va ddi nang trung tam va tir D6ng - Tay den Tay Bae D6ng Nam phan phia Nam (Hinh 5) O be Nam C6n Son, img suat ngang cue dai c6 hudng D6ng Bae - Tay Nam d phia Bae va Bae - Nam d phan Trung tam ciia be (Hinh 6) Mgt bang chiing ve hudng img suat ngang cue dai D6ng Bae - Tay Nam d phan phia Nam cda be Nam C6n Son la hien tugng phun d mo Lan Tay nam 1993 Khao sat sau muc nude bien phia tren md cho thay cac noi phun tim thay gan nhu nam tren cac dudng thang CO hudng D6ng Bae - Tay Nam (Jakopsson v^ n.n.k., 1995) Cac vi tri phun d m6 Lan Tay co the hieu nhu la niit vd thiiy luc ty le ldn Hudng ciia khe nut bi gay phun phii hgp vdi hudng img suat ngang cue dai hien tai D6ng Bae - Tay Nam 107°E 107°30'E 108°E 108°30'E 10"30' N 10°30't 10°N 10"N 9°30'N 9"30' N 107°E 107°30'E 108°E Hinh 5: Hu'OTig iing suat ngang cue dai be Ciru Long 108°30'E 544 Trudng ung suht hien tai v^ dp suat he bl Ciru Long va Nam Con Sffn, IO7OE IO8OE IO9OE Xac djnh tir hudng sap la gieng khoan Xac djnh tir huang nut ne sinh qua trinh khoan Xac dmh tu huong noi cac diem pht 90N 90N 8ON 80N '70N 70N IO70E IO8OE IO90E Hinh 6: Hvong irng suit ngang eve dai be Nam Cqn Sorn Tuygn tap bao cao H^i nghj KHCN "30 nSm Dau Viet Nam: Cff hoi mdi, thach thiic mdi' 545 AP SUAT T H A N H HE TRONG BE CUtJ LONG VA N A M C O N SON Ap suat he thu dugc xac dinh tir tai lieu thir via RFT va DST d cac gilng tham va khai thac De tranh anh hudng cua sir suy giam ap suat via qua trinh khai thac, cac tac gia kh6ng sir dung tai lieu ap suat ciia cac gieng khai thac Ap suit he be Cim Long gan bang ap suat thiiy tinh trir tang Oligocen tren (Hinh 7) Ap suat h? Ap suit thuy tinh 500 IJngsu at thiuig duqg 1000 ; • • hieu sa " V-i j \ 2000 2500 3000 t 01igo> en I vy" + + thu-fl 3500 I -At \ + > \ 4000 !\ 4500 20 40 Hinh 7: 60 80 100 Ap suat (MPa) Trong be Nam Con Son, ap suit he co gia tri thay d6i tir tuong duong vdi ap suat thuy tinh den ap suit cao va tham chi rit cao mgt s6 gilng Phin ap suit cao dugc quan sat tir sau tren 1100m d phin Nam va 2500m d phin BIC ciia bl (Hinh va 9) Tru-oTig ung suat hien tai va ap suat he bg Ciiu Long va Nam Con Soiy^ 546 w i '1 500 1000 1500 \iI \ i 3 x: U 2000 \ 2500 • \ \ X •• • i \ * X 3000 \ !• 3500 V 4000 40 20 60 80 100 Ap suit (MPa) Gieng khoan A2 Gieng khoan Al Gieng khoan A3 Ap suat thuy tTnh Gieng khoan A2-1 ifng suat thang diing Hinh 8: Di thircmg ap suat 6" phan nong quan sat diro'c i .A mot so gieng khoan be Nam Con Son Tuygn tap bao cao Hpi nghj KHCN "30 nam DSu Viet Nam: Cff hoi mdi, thach thiic moi' 547 1000 B 2000 «0 (/> 'sz 3000 o 4000 5000 20 40 60 80 100 120 140 Ap suit (MPa) a % Gi^ng khoan B6 X Gi4ng khoan B I I • Gi6ng khoan B3 Gi4ng khoan B2 Gi^ng khoan B13 • x Gilng khoan B7 U'ng suit thing dipng Gilng khoan B5 Ap suit thuy tinh • Gilng khoan B14 D Gilng khoan Bl5 Hinh 9: Di thiro'ng ap suat ff phan sau quan sat duffc mot so gieng khoan be Nam Con Son CU^OfNG DO ITNG S U A T TAI CHO CAC BE CUtJ LONG VA NAM CON SON De don gian hda, cac tac gia chi xac dinh ba phan iing suat chinh hai be tram tich Neu img suat thang dung dugc chgn la mgt cac img suat chinh cua vimg nghien ciiu, thi hai iing suat chinh lai la cac iing suat ngang cue dai va iing suat ngang cue tieu L Cu'o-ng irng suat thang dirng (hay irng suat de nang Sy) ling suat thang diing tai bat ky sau z nao ciing dugc gay bdi trgng lugng cua cot nude bien va dat da nam phia tren diem U'ng suit la tich phan mat nude biin va mat kh6i ciia da theo sau dugc xac dinh bing phuong trinh sau: 548 Tru-Q-ng u-ng suat hien tai va ap suSt he bl Cihi Long va Nam Con Son^^-^ ( Z Z ^V =A\^^ Pseadz + |^ ' p^dz (1) Trong do: Sy la ling suat dge, ZB la sau day bien, Pb la mat kh6i cua da theo carota mat do, Psea la ty trgng nude bien, va g la gia t6c trgng trudng Tai lieu carota mat thudng d phan sau cua gieng khoan Ci cac gieng khoan kh6ng CO tai lieu carota mat d phan n6ng, cac tac gia sir dung gia tri mat do dugc tir cac gieng khoan lan can T6ng hgp tai lieu tir cac gieng khoan be, cac tac gia xay dung mat cat iing suit da phu theo sau va phuong trinh thuc nghiem (2) de tinh img suat da phii cho cac gilng khoan kh6ng co tai lieu mat Hinh 10 the hien mat cat img suat thang dimg theo sau d be Nam C6n Son S 1.1066 = 0.00093* (z)' (2) 500 \ Sv =0.0093'*De pth'^1.1066 = 0.999 1000 1500 40 1 1 2000 O 2500 3000 ! i_ ; • •• i ' : i 3500 i i : 20 40 60 ^ ^ ^ 4000 80 100 Ap suit (MPa) Hinh 10: iTng suat thing dirng o" be Nam Con Son Tuygn tap b^o cao Hgi nghj KHCN "30 n2m Phu Vi^t Nam: Cff hoi mdi, thach thuc mdi" 549 CiroTig irng suat ngang Cudng img suit ngang cue tiiu (Sh) dugc bing cac ky thuat nirt via thiiy lire nhu thir vd via cac ldp cat ket Lfng suit ngang cue tiiu (Sh) dugc xem la bang ap suat khep kin khe mit (Pc) (Gjonnes va n.n.k., 1998) Sh=Pc (3) Trong qua trinh thir, ap suat cot dung dich dugc nang dan len bang each bom dung dich vao gieng khoan va vao khoang thir Khi gieng khoan bat dau nirt co hien tugng mat dung dich thi dimg bom va theo doi sir suy giam ap suat Ap suat tai diem thay doi d6c tren dudng cong suy giam ap suat chinh la ap suat khep kin khe nirt Ap dung phuong phap ciia Lee va Haimson (1989), cac tac gia xay dung thi quan he gitra dao ham ap suat theo thdi gian (dP/dt) vdi ap suat sau ngimg bom dung dich (P) Tren thi nay, sir suy giam ap suat trudc va sau ddng khe nirt thay d6i theo hai ham tuyen tinh khae Ap suat khep kin khe niit nam tren diem giao ciia hai dudng tuyen tinh dd (Hinh 11 va 12) 7000 c (PSI) 6900 6800 - - -• - - ~ - "• O) c — 6700 X O) " •" V 6600 (0 a < X 6500 _ ^ - X -X 6400 _X ^ X 6300 Thai gian sau ngu-ng bam (phut) Hinh 11: Su- thay doi ap suat day gieng sau ngirng bom thu* v& via tai gieng khoan Al be Nam Con Son 550 Tru-6-ng ung su^t hien tai va ap suit thajihJi|n;ong bg Ciiu Long va Nam Con Son, ^ 300 c m 250 O) •-6 x: *.• o