Tuygn tap bdo cao Hdi nghj KHCN "30 nam Phu khf Viet Nam Co'''' hdi mdi, thach thiic mdi" 415 N H L T N G V A N D E T H A M DO DAU KHI 6 VIJNG RIA BE C U U LONG Hoang Ngge Dang Lam Son JOC TOM TAT Ddi v&[.]
Tuygn tap bdo cao Hdi nghj KHCN "30 nam Phu khf Viet Nam: Co' hdi mdi, thach thiic mdi" NHLTNG V A N D E T H A M 415 DO D A U K H I VIJNG RIA BE C U U LONG Hoang Ngge Dang Lam Son JOC TOM TAT Ddi v&i cdc md ddu hiin dang khai thde & bi Ciru Long, trir md Rdng ndm & ria Tdy Nam bi vd cd mdng tuong ddi ndng, cdc md cdn lgi diu cd mdng vd tdng Oligocen ndm khd sdu De phuc vu cho cdng tdc thdm dd & ria bi, viec nghiin ciru su thay ddi tuo'ng trdm tich cung nhu su thay ddi thdnh phdn thgch hgc tir cdc d&i trung sdu cd nhiiu giing khoan d&i ria la rdt quan trong, nhdt la viec ddnh gid khd ndng chua vd chdn cua d&i ria Bdo cdo dua vd thdo ludn vi su gidng vd khdc eua cdc yiu td thdnh phdn he thdng ddu giira cdc triing sdu vd d&i ria bi, tir d& rut mdt sd diim ddng liru y thdm dd d&i ria bi D&i ria bi c& nhiiu diim khdc so v&i cdc d&i trung sdu, ngodi nhirng yiu td mang tinh quy lugt nhu trdm tich cd hgt thd hon dnh hu&ng din tinh chdt sinh chua chdn thi tinh nut ne cua mdng cung khdc, vi vdy thudc mdng & d&i ria thiin vi tinh chdt chua hay chdn se ldm thay ddi hdn quan diim vi thdm dd & vung ndy Tuy nhiin, d&i ria bi cung khdc tir vung ndy den vitng khde, dac diim kiin tgo vd ngudn trdm tich khdc Cdc bdy cdu tgo o vung ria thuong cd kich ea nhd, vi vdy nin khuyin khich thdm dd cdc bdy dia tdng vd chi cd kiiu bdy ndy m&i cd khd ndng gia tdng ddng ki trir lugng ddu bi, kiiu bdy dia tdng ddu tiin nin dugc chu y Id dgng cdc fan cdt & cdc dia tdng khdc Cdc phucmg phdp dia vgt ly dac biit tren tdi lieu 3D la cdng cii hiru hiiu thdm dd & vung ria MO D A U Be Cim Long la be dau quan trgng nhat a nuac ta (Hinh 1) va phan Ion san lugng dau hien dang dugc khai thac a be a cac mo Bach H6, R6ng, Rang Dong, Su Tir Den va H6ng Ngge Trong tat ca cac mo ke tren, d6i tugng khai thac ehii yeu tir tang mong nirt ne va mgt phan quan trgng tir tang cat ket Miocen duai (Hinh 2) O nhieu noi, mac dii da duge phat hien ehiia san pham dau khi, song cac tap cat ket Oligocen tuong dong chay (channel) va alluvi hien chua dugc dua vao khai thac tinh lien th6ng via ciing nhu r6ng, tham kem Doi vai cac mo dau hien dang khai thac a be Cim Long, trir mo R6ng nam a ria Tay Nam be va co mong tuong d6i n6ng, cac mo lai deu c6 mong va tang Oligocen nam kha sau De phue vu cho c6ng tac tham a ria be, viec nghien CIJU SU thay d6i tuong trAm tich ciing nhu sir thay d6i phAn thach hgc tir cac dai triing sau eo nhilu gilng khoan dai ria la rat quan trgng, nhat la viec danh gia kha nang chiia va chAn ciia dai ria Bao cao dua va thao luan vl sir gilng va khae ciia cac ylu t l phAn 416 Nhung \'hn dk tham dhu d viing ria bg Ciiu Long he thing dAu giiia cac triing sau va dai ria be, tir rut mgt s l dilm dang luu y tham dai ria be Dia tAng eua bl Cim Long da dugc de cap rat nhilu xuAt ban pham vi vay chung t6i nghT rAng kh6ng can phai nhac lai Trong bao cao ehiing t6i sir dung cac tap dia chAn A, B, C, D, E, F nhu la cae don vi dia tang phan tap ca sa Qua lich sir tim kilm tham d6 va cae phat hien dau a bl Cim Long, nliieu nha dja chAt da ting kit rAng "Tai cac eau tao thuoc be Cim Long, a dau eo set D va set Bach H6 tit, a CO dAu mong mit ne va cat ket Miocen duai" Tir nhan xet co tinh quy luat tren, dii vai viing ria bl, cau hoi dat la lieu co set D va set Bach H6 co chat lugng tit kh6ng? va tir xem xet dii tugng tim kiem, tham dau la gi? Ngoai mong nirt ne va cat kit Miocen duai eon eo the tim thay dau cae loai d6i tugng nao Hinh 1: vj tri be Ciru Long va cac don vj cau triic ff *ic m6ng Hinh 2: Mat cSt Bach H6 va doi tucmg tham thoi gian qua D6i voi be Cim Long, kha nang sinh ciia da me la cue t6t nen bat ky kieu bay nao hgi dii hai ylu t l chiia, chAn diu co kha nang tim thAy dau khi, kh6ng nhat thilt chi la mong va cat Miocen duai (B1), ma ca nhung dia tang khae Nhieu nha nghien ciru Tuygn tap bao cao Hdi nghj KHCN "30 nam P^u Viet Nam: Co hdi nidi, thach thiic mdi" 417 cho rAng cAn lam ro han lich su dia chat c6 dia ly tucmg da qua tirng thai k\\ nham huang lai tim kiem tham bay dia tang J rong tham dau co nhung ngu\ en ly ve phat hien mo dugc riit nhu sau: - Phan ion tru lugng ciia be nam cac mo lan - Cac mo lan ciia mgt play thuong tim thay sam tham play - Tiep tuc tham se tim cac mo nho han - Tu tuang dia chat va c6ng nghe he th6ng hoa viec phat hien mo - Tu tuong mai va e6ng nghe moi lam tang tiem nang phat hien mo Soi minh vao nhung nguyen ly tren dieu lam chimg ta phai su\- nghT \a tran tro la chung ta se tham tiep tuc a be Ciru Long nhu the nao? Cac mo mai se phat hien co kich CO bao nhieu va nam play nao? Lieu chiing ta co the co tu tuang gi mai khong va nen ap dung c6ng nghe gi nham phuc vu cho tu tuong tham mai ciia chiing ta? CAC QUAN DIEM T H A M DO vA KET QUA T H A M DO BE CUU LONG TRONG THOI GIAN QUA L Mong Khi mong ciia mo Bach Ho dugc phat hien nhu la d6i tirgng chira dau nam 1988 da lam ngac nhien cac nha dia chat tham va cang ngac nhien han mong la tang san pham chinh, chiem han 80% san lugng khai thac ciia mo Tuy nhien, cho den tan nhung nam 1991 - 1992, nhieu nha dia chat van coi la mgt hien tugng di thuang va van rat hoai nghi ve kha nang chii'a dau cua cac eau tao khae lan can a be Cuu Long, vi vay ma cac 16 15.1, 15.2, 16.1, 16.2 de mo mgt thai gian kh6ng duge cac cong ty dau quan tam Khi C6ng ty JVPC phat hien mo Rang Dong Petronas phat hien mo Rub} nam 1994 thi lap tii'c cae 16 ma a be Cim Long nhan dugc moi quan lam dae biel ciia cac nha dau lu va da co su canh tranh kha quyet liet de co dugc hgp dong tham dau a be vi cac nha dia chat hieu rang d6i tugng mong chira dau kh6ng phai la hien tugng di thuang, ma co the eo a nhieu cau triic be Tiep theo la giai doan d6i tugng mong dugc coi la d6i tugng tham chinh va gan nhu 100% cac gieng khoan tham deu khoan vao d6i tugng va mgt s6 mo mai da dugc phat hien nhu R6ng, Su Tir Den, Su Tir Vang, Phuang Dong Tuy nhien, a nhieu cau lao khae da khong tim thay dau ehira a mong va lir da huang lu tham den cac dieu kien nhat dinh de dau co the nap ehira va bao l6n mong Da chiia h.ic nguyen Tang chira cat ket Miocen duoi a mo Bach Ho dugc Mobil phat hien lir nam 1975 sau XNLD Vietsovpetro phat hien them 10 via cat kel Oligocen a \om BAC Bach 116 Tang chira cat ket Miocen duai la lang chira quan trgng thir hai be Cuu Long dugc phat hien va khai thac a cac mo khae nhu Ring, Rang D6ng, Rub\ \ a Su u Den 418 Nhung vin de thSm dd d§u d vung ria bl Ciiu Long Cho din nay, nhieu via chiia cat ket Oligocen thuge cae tap dia chAn E, D, C dugc phat hien a cac mo Bach H6, R6ng, Su Tir TrAng, Rang D6ng, Su Tir Den, nhien chung chua dugc chu y khai thac chat lugng da chira va tinh lien th6ng via kh6ng t6t bAng mong va cat ket Miocen duai Net dac trung nhat cua c6ng tac tham dau a be Ciru Long thai gian qua la: - Tap trung vao cae eau tao dang vom ke thira mong - Doi tugng tham ehi ph6i tu tham d6 la mong, tiep theo la cat ket Miocen duai - Mo hinh mau cho tu tham la mo Bach H6 Trong qua trinh tham cho den co mgt s6 diem khae biet (Hinh 3), lech khoi m6 hinh mau Bach H6 la: - Trong mong, chi co m6 Bach Ho nhin thay diit gay nghich va co hien tugng nhiet dich xay manh nhat, a cac mo khae viec tao khe nurt mong thuan qua trinh kien tao gay va thuong di kem vai cac durt gay thuan - Tinh chat tham chiia thay d6i mong, chi tot dge theo mgt so dut gay, a nhieu noi, kh6i mong van chi la mgt kh6i chat sit - Co khu vuc CO ty le khi/dau cao la Su Tir Trang, Phuong Dong, Emerald, nguge lai CO khu vuc CO ty le khi/dau thap la Su Tir Den, Su Tir Vang - Cat ket tang E, F a Su Tir Trang, tang C or Su Tir Den eho dong thir via cao, chimg to tinh chat tham chiia rat t6t eua via - Cat ket tang Bl (Bach H6) co chat lugng chiia t6t a giiia triing, nguge lai co chat lugng kem a mgt s6 gieng khoan a dai ria, dieu nguge vai quy luat tram tich Hinh 3: Nhan xet ve nhirng khae biet be Ciru Long Vai nhung nhan xet tren, tac gia muln luu y rang viec nhan biet tinh tuong tu ciing nhu tinh phan dj a nhiing mo, nhung cAu tao da khoan se giup chiing ta co cai nhin khaeh quan cho giai doan tham tilp theo 419 Tuygn tap bao cao Hdi nghj KHCN "30 nam P5u Viet Nam: Co hdi mdi, thach thuc mdi" NHtTNG NHAN XET VE DAC DIEM TIEN HOA BE v A MOI TRU^ONG T R A M TICH, c A u TRUC Qua nghien ciiu lich sir phat trien dia chat be Cim Long Kainozoi, hau het cac nha dia chAt diu ding y rAng be da trai qua mgt giai doan tach gian vao Eocen - Oligocen va mgt giai doan bi nen ep vao cu6i Oligocen - dau Miocen, sau la giai doan sut liin nhiet va binh 6n kien tao (Hinh 4) Dac diem n6i bat ciia be Cim Long nhu mgt be rift ngi lire la tach gian khong qua Ion, ehi dii de phan di dia hinh mong va nen ep ciing kh6ng qua manh, chi dii lam bien dang nhe lap phu tram tieh, kh6ng gay cae nghich dao kien tao va eat cut nhu a cac be khae khu vuc -1100 -leoo -IBOO Hinh 4: Mat cat the hien sy tach gian va nen ep be Cu'u Long Cac pha tach va phan di moi tru-cmg tram tich Giai doan tach gian Eocen - Oligocen the hien ro nhat qua hai tap dia chan E va D, CO cac thuge tinh dia chan khae han ciing nhu dugc tao cac m6i truong tram tieh khae va giiia chiing la bat chinh hgp goc M6i truong tram tich ciia hai tap the hien sir ke tiep cua moi truang luc dia theo huong ma rong khong gian tram tich tir nh6 hep den rong Ion, vi the co the coi giai doan tach gian bao g6m hai pha: pha dap va tao tap E va pha gian ma rong tao tap D, d6ng thai co su thay doi true tach gian tir huong D6ng - Tay sang D6ng Bae - Tay Nam vao cu6i Oligocen Tap E hinh nhu tang lot day giai doan dau dap va day be vai dia hinh la cae ban dia hao, dia hao (kh6i triing) xen kep vai cac dia liiy (kh6i eao), eae kh6i triing dugc lap day nhanh bang cae tram tich vun th6, niii lira va tram tich niii vai ngu6n tram tich tir cae khoi cao ke can nen dac diem tram tich mang tinh dia phuang theo dia hinh c6, chua hinh mgt be Ion co trung tam tram tich va viing ria (Hinh 5) Tap D hinh pha gian mo rong giai doan tiep theo, cac kh6i trung dugc ma rong, sau dan va lien th6ng tao nen mgt bien h6 rong Ion co ba ria xung quanh va tiep nhan tram tich tir xa vao Xet vl chilu thAng dung, phan tram tich tap D dan tir duai len tren, img vai qua trinh gian ma rong bl va xet theo chilu ngang phan tram tich tap D th6 dAn tir trung tam cac dai ria (Hinh 6) Nhdng van de tham dd dhu d viing ria he^ini^Long 420 bARli.VUHGTaL Hinh 5: Ban co dia ly tap E BA R1« VUNO T * U Hinh 6: Ban co dia ly tap D Cac pha nen ep va anh huong den cau triic Giai doan nen ep a be Cim Long the hien ro nhat qua hai lap dia chan C va Bl chimg CO Ihugc linh dia chan phan lap song song, tuong d6i gi6ng nhau, nhung giira chung cung la bai chmh hgp goc lap C ihe hien su nen cp qua bieu hien bao mon cat cut qua cac khoi nho cao va co be da> iriim lich tha\' d6i rat khae a cac doi trung di kem vai su bien dang nghich dao cua cac lap L \ a D a ben duoi va thuang xa\ a eae khu vuc dang ban dia hao Day la giai doan the hien su ep d6n, oan vong cua be Cuu Long va no xay irong mgi giai doan ihiri gian Tap Bl Ihe hien su nen ep qua su lai hoat dgng cua he thong dirt gay a dang ep chom lao nen cac cAu iriic "Iroi" cac cAu tao am/duong hinh hoa, phai Irien manh hern a phiin Bcic be Tuygn tap bao cao Hdi nghj KHCN "30 nam Pau Viet Nam: Co' hdi mdi, thach thiic mdi" 421 Cac phu doi trSm tich Co the chia dien tieh be Cim Long ba phu dai trAm tieh va chiing khae ehu yeu la ngu6n tram tich va huong van chuyen khae la phu dai Tay, D6ne va BAC (Hinh 7) BARIA-VUWtlTAU Hinh 7: Ban cac doi tram tich a Phu d&i Tdy - NAm a phia Tay bl, gom nhung trung nho, hep dge theo he thong dirt gay D6ng Tay - NguIn trAm tich chii ylu tir nang Khorat, mgt phAn tir dai Da Lat - Mgt cac trung tam trAm tich cua tap E b Phu d&i Dong - NAm a phfa D6ng bl, kep giira dai nang Tmng tam va nang Con San - Ngu6n tram tich ehu ylu tir nang C6n San - Mgt cac trung tam trAm tich cua tap E, D c Phu d&i Bde - Nam a phia BAC be, gom mgt loat triing tir Ion din nho, dge theo he thing dirt gay D6ng Bae - Tay Nam - Ngu6n tram tieh chii ylu tir dai Da Lat - Trung tam trAm tich ciia cac tap D, C, B1 BAN VE H E THONG DAU KHI DOi RIA BE vA cAc VAN DE T H A M DO DAU KHI He thing dau co hai phAn chinh la: 1) sinh, nap va 2) bay (ehira, chAn) va dl ban ve cac van de tham dAu or dai ria bl chiing ta cAn xem xet hai Nhung v§n dl thSm dd dau d viing ria bg Ciiu Long 422 phAn tren ciia he th6ng dau khae biet nhu the nao giua viing trung tam va dai ria be (Hinh 8) Bach^oReW rSinh,ii^_ -;~=3f^KSh-^ r i ^ ^ ^ ^ ^ K j i - i ^ - JSC|?^gP>- Nap- 'ftl^ejig^A.^irngfin j ~ ; ^"—-TGSnSi i.tf^)ai^