Đặc điểm trầm tích khu vực Trường Sa và lịch sử hình thành

PETROVIETNAM<br /> <br /> <br /> <br /> <br /> Oac diem tram tich khu vyc Truang Sa<br /> va lich SLT hinh thanh<br /> KS. Nguyin Quang Viet, ThS. Le Trung Tam<br /> KS. Nguyin Thi Tra Giang, KS. Nguyen Van Hoang<br /> Tong cong ty Thdm do Khai thdc Ddu khi<br /> 1. Gidi thieu ehung<br /> <br /> <br /> <br /> <br /> 104' 106 108* 110' 112- 114- 116- 118- 120*<br /> <br /> <br /> <br /> -60 -30 0 30 60 90 120<br /> Free air anomalv (moall<br /> Hinh 7. Khu vUc Trudng Sa tren bdn do di thudng trgng lUc (theo Nguyen Nhu Trung vd nnk)<br /> Khu VL/c (Jao Truang Sa dac tri/ng bdi cac dai da vol trong khu vUc dUac gol la Reed Bank.Trong khu vUc da co<br /> phat trien tren nhUng ddi nang co (paleohighs) bao 7 gieng khoan tren cac dai da vol trong do co mot so<br /> quanh la khu vUc nuoc sau xa bo. Dai da voi Ion nhat gieng da phat hien nhUng via khi<br /> <br /> <br /> <br /> DAU K H i - S O 2/2011 15<br /> THAiWi D 6 - KHAI THAC DAU KHi<br /> <br /> <br /> <br /> <br /> ReedBank ReedBank Kalamansl Sampaguita Sampaguita 2. Dja tang tram tich<br /> -AI -BI -1 -1 -3A<br /> <br /> Qua trinh tien hoa dia chat cua<br /> khu VUc lien quan trUc tiep tdi hoat<br /> Miocen m dgng kien tao tach gian va troi dat<br /> khoi luc dja chau A. DUa tren ket qua<br /> Oligocen thtrQnng ==. minh giai dia chan trong khu vUc cho<br /> thay cac tap tram tich chinh:<br /> Olisocen ha<br /> Paleocen - Eocen<br /> Paleocen ha 1. Tap tien Oe tam (Creta).<br /> Kreta<br /> 2. Tap tram tich dong tach gian<br /> (Paleocen - Oligocen muon).<br /> <br /> 3.Tap tram tich trong pha troi dat<br /> (Oligocen muon - Miocen giCfa).<br /> <br /> 4. Tap tram tich sau tach gian va<br /> lijn chlm nhiet (Miocen muon tdi<br /> nay).<br /> <br /> Hinh 2. Lien ket dia tdng trong cdc gieng khoan tgi Reed Bank Hinh 2 the hien sU lien ket dja<br /> tang khai quat cua cac gieng khoan<br /> Cot dja tang long hop khu vyc JMSU<br /> trong Reed Bank.<br /> <br /> 2.1. Thdnh tgo trUdc De tam<br /> <br /> Tuy cac thanh tao tuoi Paleozoi<br /> Thanh tao am tieu tdi Mesozoi giijfa chUa dugc khoan tdi,<br /> tren khoi nang noc<br /> nhUng theo tai lieu dja chat khu vUc<br /> Synrift.<br /> Thanh tao cacbonat cho thay cac thanh tao trUdc De tam<br /> them vao cuoi cd the la hon hgp cua tram tich<br /> Oligoxen. Mioxen Mesozoi va co hon vdi thanh phan<br /> som.<br /> bgt ket, cat ket va da set tuoi Triassic<br /> Thanh tao cat<br /> Turbidite muon - Jura sdm; cac da macma<br /> Set bien tham (Diorit, Olivine, Gabro), vdi nhCfng dai<br /> bien chat dja phuong (Gonai, Oa<br /> phien, va Philit tuoi Creta sdm, va da<br /> phien tuoi Jura), dong thdi cac mau<br /> Thanh tao tuong dam mai trong khu vUc dat hiem<br /> lay chiia than, vung (dangerous ground) cho thay rang<br /> vinh tram tich trong khu vUc dugc bat dau<br /> Set va set voi bien.<br /> tLf Mesozoic muon (Kudrass va nnk,<br /> 1986). Tap tram tich nay cd lien quan<br /> chat che tdi cac phan vj tram tich<br /> cung tuoi dugc tim thay trong cac<br /> Gap cac thanh tao luc bon trung ngoai khoi Trung Quoc.<br /> dia den bien nong.<br /> Cac phan vj tram tic- -,.ay g^j^^ p^gn<br /> chia vdi nhau bdi ca .-, ^t Th hop.<br /> Hinh 3. Cot dia tdng tong hgp khu vUc Trudng Sa Ket qua nghien cUu chua kt -, ^jph<br /> <br /> <br /> <br /> 16 oAUKHi - s o 2/2011<br />  PETROVIETNAM<br /> <br /> <br /> <br /> <br /> C6sa tuang dong cua tram tich Kreta hg khu vac Trudng Sa vdi cac thanh tgo cOng<br /> tuoi d cdc thanh he Baidhong (tudng dam ho) gap d Heshan, Quang Dong<br /> <br /> Hinh 4. Mau vun khoan trong tram tich Creta hg cd mdi trudng thdnh tgo tdluc dia den bien ndng (GK Kalamamsi-1 & Sampaguita 3A)<br /> <br /> <br /> dugc cac thanh tao da mdng grannit trUdc De tam phong 2.2. Tap trdm tich dong tdch gidn - Synrift sequence<br /> phll d Nam Viet Nam cd phan bo den khu vUc ReedBank<br /> Tap nay dUOc bat gap d nhieu gieng khoan t r o n g<br /> hay khdng. NhUng kha nang cac thanh tao Ophiolite bat<br /> cac bon t r u n g ngoai khoi Viet Nam va khu vUc. Ranh<br /> gap d dao Palawan se cd the xuat hien dTay Bac khu vUc,<br /> gidi cua tap tram tich nay vdi tap tram tich trudc tach<br /> dugc hinh thanh trong pha htJt chim phuong Tay Bac m d ra<br /> gian dugc ngan each nhau bdi m g t bat chinh hgp.Trong<br /> bien Ddng hien nay va khdng lien quan tdi thanh tao da<br /> khu vUc, thanh phan thach hoe eua tap chu yeu la eat<br /> mdng d Nam Viet Nam.<br /> ket bgt ket va set ket xen lan nhau dugc thay t r o n g cac<br /> Ket qua cua gieng khoan sau nhat (Kalamansi-1 vdi<br /> gieng khoan. Phan dudi eung cua tap dugc lang d g n g<br /> do sau 4436m) vao tram tich Creta sdm, cho thay sU pho<br /> cung vdi tram tich bien sau, t r o n g ehu ky bien tien vdi<br /> bien cua cac thanh tao bien trong mdi trudng nudc nong<br /> thanh phan thach hgc la cat ket va set ket t u o i Paleocen<br /> cd thanh phan thach hgc la bgt ket vdi va cac Idp set vdi<br /> tdi Eocen sdm. Tiep theo chu ky bien tien la chu ky bien<br /> phan Idp mdng chifa phong phu cac hda thach thuc vat.<br /> thoai vdi phan day eua chu ky la eae t h a n h tao tram tieh<br /> Thanh tao Creta thudng vang mat trong cac gieng tien chau t h d . Cang len phia tren cua tap, cac tram tieh<br /> khoan Kalamansi-1, Reed Bank A-1 va Reed Bank B-1. Cac ed thanh phan la eat ket t r o n g mdi trUdng chau t h o ,<br /> thanh tao trudc De tam cd chtfa cat ket mau xam, bdt ket sdng eung vdi set ket va than duge lang d g n g . Tai gieng<br /> va set ket. Cat ket cd kich thude hat trung binh den thd, khoan Reed Bank B-1 bSt gap cac tram tich hat vun<br /> do chgn Igc kem. Cat cd chiJa cudi sdi nhd va da vdi ket Paleogen xen kep vdi set ket va m d t it eat ket; t r o n g khi<br /> hach vdi ham lugng thay doi nhUng ludn cd mat trong cac do phan d u d i eua t h a n h he nay tai g i e n g khoan<br /> mau lay t i / 3157,7 tdi 4123,9m t r o n g gieng khoan Kalamansi-1 bao g d m bdt ket va set bdt ket ehda vdi.<br /> Sampaguita-1. Tram tich vun Creta ha thude mdi trudng Phan day eua Eocen giUa la set ket cd do cdng n h u n g<br /> bien ven bd tdi nudc Ig (3349,8 - 3962,4m trong gieng gidn, mau xam den. Tai do sau 2131,5 - 3157,7m, ea hai<br /> khoan Reed Bank B-1). Trong khu vUc South Bank (Reed gieng khoan Kalamansi-1 va Sampaguita-1 deu bat gap<br /> Bank) bat gap cat ket va da manh vun xen kep vdi da mgt loat cac tram tieh hat t h d day lang d g n g t r o n g mdi<br /> phien va than da. Trong phan phia Bac Reed Bank, tram t r u d n g ven bien tU ddi tren trieu den ddi dudi trieu.<br /> tich mjn hon va vang mat than. Nhu vay, nhin ehung Trong khi d d gieng khoan Reed bank A-1 da khoan vao<br /> thanh tao Creta bao g o m tram tich tUdng sdng-chau tho cac tap cat xen kep vdi bdt ket va set ket t u o i Eocen<br /> tdi bien ndng. t r u n g lang d g n g t r o n g mdi t r u d n g bien rla. Cac tap cat<br /> <br /> <br /> DAU K H i - s o 2/2011 17<br /> THAM DO - KHAI THAC DAU KHI<br /> <br /> <br /> <br /> <br /> thach anh (Quartzose) nay la bang<br /> 10 km B-DB<br /> N-TN<br /> chUng eho n g u d n gdc luc dja. Trong<br /> Sampaguita Kalamansi Reed Bank<br /> gieng khoan Sampaguita - 3A, vang<br /> mat tram tich t u d i Eocen giiJfa.<br /> <br /> 3 . D j a t a n g p h a n t a p v a nguon<br /> g o c lien q u a n<br /> <br /> Thdi ky tach gian 6 Nam bien<br /> D d n g ndi ehung dUOc bat dau trong<br /> c sudt Paleocen va ket thuc vao Oligocen<br /> E sdm (Holloway, 1982). Tren mat cat dja<br /> chain bat chinh hop dUdi cua tap ddng<br /> tach gian la ndc De tam. Trong loat<br /> ?t.^,i'-'.^*;-ittw*^r*-=?;i'.^viif*&«^ ddng rift, nhin ehung cd 4 tap, dugc<br /> xae dinh tren co sd cac be mat ke ap.<br /> E J h i m nbng<br /> (Neritic)<br /> rrerrestrial) Trong mdt nhdm cua cac mat cat, moi<br /> ro tap dac trung cd mdt tUdng nCfa trong<br /> sudt d dudi va Idp khdng trong sudt d<br /> phia tren (do phan xa cao). Noi day<br /> nhat cue bd khoang 2 giay (Hinh 5).<br /> Hinh S. Lien ket mdi trudng trdm tich synrift vd Creta hg qua cdc Day cua tap 2 va tap 4 dugc dac trUng<br /> cdu tgo dd khoan trong khu vUc (Sampaguita - Kalimansi -ReedBank)<br /> bdi sU cat cut do xdi mdn dja phuong.<br /> <br /> NhUng phan sutcua tap 3 va4the<br /> hien cac dac diem dja chan turbidite<br /> gidng dang quat day bien, do doc<br /> phiJc tap (Hinh 6, 7), va thung lung bj<br /> khoet sau (incised valley fills) (Hinh 7).<br /> <br /> Dang dja hinh nghieng Idn dUOC<br /> quan sat trong thdi ky mUc nude bien<br /> thap eua tap 3 (ed dang.ehiJ S) va day<br /> eua tap 4. Chieu cao eua dang dia<br /> Hinh 6. Mat cat dia chdn phdn tap trong SynRift<br /> hinh nghieng lan dan ra bien (the<br /> heigh of the progading clinoform)<br /> cua tap 3 thay ddi tir 0,8 den 1,1 giay,<br /> ehCfng minh do sau mUc nUdc co khac<br /> nhau tCr 1600m tdi 2200m tii toplap<br /> den downlap. DUa tren hUdng<br /> dow/nlap, hUdng ngudn gdc ehung la<br /> tir Tay (Hinh 6).<br /> <br /> Mdt bieu do Wheller dugc xay<br /> dung de chi ra, gian doan tram tich d<br /> giUa va sU ed dac ben trong tap (Hinh<br /> 8). Bd phan chan t d t - at thanh he la<br /> Hinh 7. Tren phdn cao cua sequence quan sat thay cdc kenh (den 5km) nhdng bd phan cd c (gp |^^^<br /> (theo gido sd Bao Minh) hgp vdi be mat ngap < j<br /> <br /> <br /> <br /> 18 D A U K H I - S O 2/2011<br />  PETROVIETNAM<br /> <br /> <br /> <br /> <br /> gieng khoan nay deu dugc khoan tren<br /> cac dai cao (bank), nen khdng dai dien<br /> tram tich het eae thanh tao trong khu VL/C. Cd<br /> the suy luan cac tram tieh hat vun cd<br /> tuoi tuong dUong vdi tap nay cd the<br /> lang dgng d phan sau hon (Hinh 6, 9).<br /> Dge theo dao Palawan mdt tap<br /> cacbonat them danh dau thdi ky trdi<br /> <br /> Ven bd bao dat ggi la tap Nido. Cac gieng khoan d<br /> ReedBank, ranh gidi ndc Nido dugc<br /> Ven bd bao mdn lien ket tai phan thap cua tap<br /> cacbonat. Ra xa d phan sau hon, cac<br /> tap tram tich nam tren ndc Nido dugc<br /> Hinh 8. Bieu do Wheller tap trong SynRift<br /> eho la hdn hgp cuia da hat vun cd the<br /> ddng vai trd nhu mdt tang chan khu<br /> vUe kha tdt.<br /> <br /> Ndc CLia tap nay dugc danh dau<br /> bdi mdt bat chinh hgp - ggi la BCH<br /> Miocen giiJa. Bat chinh hgp nay dugc<br /> cho la do sU thay ddi cua bien D d n g<br /> t d ria mang hdi tu sang ddi hut chim<br /> trong sudt giai doan Miocen giCa<br /> (Taylor &Hayes,l 980).<br /> <br /> Trong be Tay Bac Palawan (phia<br /> Tay Bac vung nghien cdu) cung cho<br /> thay cd nhieu phat hien dau khi trong<br /> da cacbonat tudi Miocen sdm (Hinh<br /> 9). Tap cacbonat t h e m tudi Oligocen<br /> muon - Miocen sdm cung cac khdi<br /> am tieu la tang chiJa quan trgng keo<br /> dai den Ddng Bac eua Trudng Sa.<br /> <br /> Bay (07) gieng khoan tai Reed<br /> Hinh 9. Sa do mo hinh c6 taong da khu vac Traang Sa va Dong Truong Sa<br /> Bank da dugc khoan tren cung mdt<br /> (theo OXY 1995)<br /> dai da vdi vdi cung thanh phan thach<br /> 3.1. Tap trdm tich pha troi dgt va sau tdch gian hgc bao g d m toan bg cacbonat tudi<br /> Miocen muon den hien tai. Su lang dgng eua tram tieh<br /> Tap tram tich pha trdi dat ngan each vdi tap tram tich vun cd the dUOc dua ra trong mdt sd mat cat dja chan,<br /> trudc bang mdt mat bat ehinh hgp dugc hinh thanh do tuong t u n h u eae mat cat tram tieh ngoai khoi Viet Nam.<br /> qua trinh m d bien Ddng trong dd khu vUc nghien cij'u<br /> dich chuyen tuong ddi ve phia Nam so vdi dat lien chau A. 3.2. Khoi phue lich sit dia chat khu vUc<br /> <br /> Tat ca cac gieng dugc khoan trong khu vuc Reed Bank Giai doan trUdc Rift khu vUc vdi cac thanh tao chua<br /> deu chi ra rang tap nay gdm toan bd phUc cacbonat them dugc xae dinh day du. Cac thanh tao tudi Creta sdm<br /> va am tieu nam trong do tudi t d Oligocen muon tdi gan day, khang djnh trudc dd d day eung la bdn tram tieh trong<br /> cd thanh phan bao gdm limestone va dolostone d tat ca cac Mz. Bat chinh hgp va viec thieu tap tram tich Creta tren<br /> dang t d mudstone, wackstone, grainstone, boundstone trong cac gieng khoan cho thay khu vUc bi nang len t r d<br /> giau khung xUOng sinh vat, chUa eae hda thach trung Id, tao thanh luc dja trUdc pha Synrift. Dudi nay se la phan khdi<br /> thude cac mdi trudng bien ndng den them. Tuy nhien, eae phue lai tram tieh, kien tao t d SynRift den nay.<br /> <br /> <br /> DAU KHi - s o 2/2011 19<br /> THAM DO - KHAI THAC DAU KHI<br /> <br /> <br /> <br /> <br /> TUOl DIA TANG DIA T A N G DIA TANG<br /> Tlucli J<br /> he tang he tang<br /> PLEISTOXEN he tang hoc M6 ta hoc Mota hoc Mota<br /> ^HK.~-<br /> MUON<br /> :[<br /> Pliocen<br /> <br /> <br /> <br /> <br /> Them ^^IT'.''<br /> E K^>X Them<br /> x-x-z^ biem mo ^^Krl-'<br /> SOM g^wv-X bjem mo ^^^C'j<br /> . , . .( ^Bc-]<br /> <br /> <br /> <br /> <br /> SON<br /> _-_-»j<br /> <br /> MUON<br /> = tc;>::-<br /> m Khoixay am tieu<br /> cabonat-<br /> si/6n doc bien<br /> ^ HBR:<br /> ^ K - :<br /> Them<br /> <br /> <br /> <br /> <br /> i<br /> sau<br /> 'ro ^Hfr-.' Bien<br /> Chautho, tham<br /> Miocen<br /> <br /> <br /> <br /> <br /> avj.\ vung vinh OiAI-Mi o ^ K - .<br /> -ro ^ ^ L - .<br /> Them<br /> ^ro ^^^^E(-'I •-<br /> (0 ^^K'-''<br /> ^r.:<br /> SOM ra<br /> s :-:-: •b Ciiasong<br /> <br /> <br /> <br /> <br /> 1<br /> Cacbonat Q<br /> them<br /> Oligocen<br /> <br /> <br /> <br /> <br /> hlUON ....'> Song<br /> • , . •<br /> Mat bo<br /> SOM --------^ 'v'-'i<br /> Qong bang ^ • • ^ ^"_T<br /> MUON ven bo ^ " "^ Chautho<br /> Cau<br /> <br /> <br /> <br /> <br /> Song, ho Them trong m '*r-I"X-Ii -song h6<br /> c±±^^:<br /> Eocen<br /> <br /> <br /> <br /> <br /> Giir.\ Oong bangven O)<br /> '^^ bd<br /> -C i-."-"-"-*-j<br /> S6ng, hodamlay .fo u-X-X-J<br /> SOM dam lay • ^ E-X-X-J<br /> c ~ 1<br /> Paleocen<br /> <br /> <br /> <br /> <br /> MUON<br /> fc^^i- Q Sx^SS^<br /> Nuili/a :X-X-I-j Bien sau<br /> fC-Z'l'IC: Tram ti'ch<br /> SOM luc dia<br /> <br /> Be Song Pear Be Nam Con Sen Be Reed Bank Be Bac Palawan<br /> LucdiacliauA Phan troi dat Ithoi luc dia me<br /> <br /> Hinh 10. So sanh cdtdia tdng tdng hgp khu vdc ReedBank vdi cdc khu vUc xung quanh (theo PVEP)<br /> <br /> <br /> Giai doan Synrift: Day la<br /> giai doan ddng tach gian ndi<br /> lue sau pha nang len trong<br /> Creta. Mgt loai cac dia hao va • iiiio trong.<br /> ban dia hao dugc hinh thanh. SynRift<br /> Tuy theo mdc do lun chim va<br /> tach gian ma thanh tao cac<br /> tram tich t d lue dia den bien ? S * i ^ i ? ^ i >:,••• '^.>Vmii^>^im^^^•.. '^'WKr<br /> khoi (Hinh 8). Day cung la giai Hinh 11. Thdnh tgo dia hdo vd bdn dia hdo trong SynRift<br /> doan tao thanh eae dut gay<br /> trong khu vUe. Sudt qua trinh mdi trudng luc dia, tuy nhien khdng thay dau hieu nghjeh<br /> SynRift khdng quan sat thay cac bat ehinh hgp khu vUc dao trong hau het tat ca cac d u t gay (Hinh 6,11). Theo Lin<br /> cho thay qua trinh tach gian dien ra lien tue. Cac nghien va nnk (2003) sU chuyen tiep t d tach gian sang trdi dat (rift<br /> cdu cho rang giai doan cd 4 nhjp tram tich dng vdi 4 thdi drift transition) ed the gay ra sU ddi luu manti dUdi Idp tach<br /> ky thang giang mue nude bien khu vUc vao Paleocen, gian la nguyen nhan dan den sU nang len va bao mdn de<br /> Eocen sdm, Eocen gida, Eocen mudn - Oligocen sdm tao nen cac be mat bat chinh hgp trong Oligocen.<br /> (Hinh 6, 7, 8).<br /> Giai doan trdi dat va sau rift: Day la giai doan ddi tach<br /> Ket thuc giai doan Synrift dugc danh dau bdi mat bat gian da pha v d toan bd lien ket t d phan vd luc dia den<br /> chinh hgp khu vue (BCH ndc SynRift) vao giai doan dau cua quyen mem dan den qua trinh trdi dat hinh thanh bien<br /> Oligocen mudn. Cac dau hieu nen ep nhe cd the quan sat Odng t d (37-17 trieu nam theo ket qua do di th ^ n g t d<br /> d mdt sd mat eat dia chan. Gan nhu toan bd khu vUe trd ve (Taylor va Hayes 1983). Khu vuc bi lun chim nh hinh<br /> <br /> <br /> 20 DAU KHI - s o 2/2011<br />  PETROVIETNAM<br /> <br /> <br /> <br /> <br /> thanh eae tram tieh chuyen nhanh t d<br /> luc dja cudi Synrift sang tram tich<br /> bien ndng rdi bien sau. Trong giai<br /> doan Miocen sdm den Miocen trung<br /> cd sU phat trien eae t r a m tich<br /> cacbonat them va am tieu. Day bdn<br /> lun chim nhanh chdng so vdi tdc do<br /> tram tich khien chieu sau day bien<br /> hien nay khoang 2000m. Nhieu khdi<br /> am tieu khdng cdn kha nang phat<br /> Hinh 12. Mat cat khdi phue trdm tich den ndc synrift (be SE ReedBank) trien (Hinh 13) t r o n g khi tren dai<br /> Reedbank thanh tao phdc cac am tieu<br /> Nhomo! cacbonat van cdn du sde xay den tan<br /> PhJng noc tren tap synrii hien nay hinh thanh Idp cacbonat day<br /> khoang 2000m (theo cac gieng<br /> khoan da khoan trong khu vUc).<br /> <br /> Tai lieu t h a m k h a o<br /> <br /> 1. Generoso P. Revilla, Dr. Joseph<br /> Foronda, Dr. Liu Baoming, Liu Xuekao,<br /> Nguyen Viet Hung, Nguyen Thi Thanh<br /> Lam (2007). Regional geophysical and<br /> geological studies of the hydrocarbon<br /> potential of the joint madne seismic<br /> undertaking (JMSU) area. Southern<br /> South China sea.<br /> <br /> 2. Ban TKTD- PVEP (2010). Minh<br /> gidi tdi lieu dia chdn pha 3 khu vac<br /> JMSU.<br /> <br /> 3. A.TLin, A. B. Watts and S. P<br /> Hesselbo (2003). Cenozoic stratigra-<br /> phy and subsidence history of the<br /> South China Seamargin in the Taiwan<br /> region.<br /> <br /> 4. Nguyen Nhu Trung, Sang Mook<br /> Lee, Bui Cong Que (2003). Satellite<br /> gravity anomalies and their correlation<br /> with the major tectonic features in the<br /> South China sea.<br /> <br /> 5. Nguyen Trgng Tin, Nguyen The<br /> Hung, Phan TrUdng Thj, Nguyen Van<br /> Vugng, Tran Tuan Dung (2010). Tuyen<br /> tap bao cao Petrovietnam 35 nam.<br /> Ddc diem kien tgo cdc be trdm tich<br /> Kalnozoi a bien Dong Viet Nam tren co<br /> Hinh 13. Khdi phue cd dia ly qua tuyen ddc trung khu vUc<br /> sd ket qud nghien cdu mdi.<br /> <br /> <br /> Uku KHf - SO 2 / 2 0 1 1 21<br />