]SIJ DUNG PHUONG P H A P P H A N TICH A V O TRONG TIM KIEM THAM DO KHi HYDRATE VA K H A N A N G A P DUNG TAI VIET NAM
TS. N g u y i n Thu Huyen, ThS. N g u y i n Trung H i e u , ThS. Tong Duy Ci/oig KS. N g u y i n M a n h Hiing, KS. N g u y i n Danh Lam, TS. Trinh Xuan Cirimg Vien Ddu khi Viet Nam
Email- huyennl^vpi.pvn.vn Tdm tat
PhddngphdpphdntichAVO(AmplitudeVariationswithOffsethayAmplitudeversusOffsetjldphdongphdpth kiimtrifctiepcdcbaychifaddukhidifatrenkythudtphdntichbienddcuatailieudiachdntrifdckhicdng.AVOdU^
sddung ph6 bien trong cdng tdc tim kiem, thdm dd nhd khd ndng lien ket biin do dja chdn vdi ddc tinh cua dd chUa.
Cdcdithifdngbiendd(phdnxadiachdncdbiinddcaotrinmgtcdtdiachans6ngdpc)cotheduacngh.encUutnfdt khicdngdixemc6ditbddngAV0haykhdng?BiiundygiiJpphdnbietcdcdditddngdfachat(catketchifakhi,than At hay dd nui Ida) dd gdy ra di thifdng biin do.
Phifong phdp AVO dddc dp dung thanh cdng trong tim kiem gas hydrate tren the gidi nhifng chiia dugc dp dung dViitNam.Trongbdibdondy,nhdmtdcgidgidithieucasdtythuyetcuaphifangphdpphdntichAVOvdviduveket qud sd dung AVO trong tim kHm tham dd gas hydrate tren the gidi va khd ndng dp dung tgi khu viic nudc sau them luc dia Viit Nam.
Tdkhda: Gas hydrate, AVO. khu viic nUdc sau.
l . M d dau
Cic cdng tie nghien cCfu, dilu tra cd ban v l tiem nang khi hydrate cung nhu nghiin cijfu phit trien d c cdng nghi tham dd, khai thic, thu hdi tii nguyen niy dang dUdc mpt sd nUde tich cue trien khai, die biit la Canada, Mexico, Nhat Bin, My, Lien bang Nga, Han Qudc,Trung Qudc.
Khi hydrate dUpe hinh thanh v i tdn tai d eie khu vuc ed do siu nUde bien Idn (Hinh 1), ndi cd it gieng khoan tim kilm tham do ma hau nhuchi cd cac ludi tuyln dia chin. Do viy, de dilu tra, tim kilm, thim dd khi hydrate, phin tich tai lieu dia ehan se cho phep du bao sU ton tai cic ddi chijra khi hydrate.
Phuong phip du bao eae ddi chura khi hydrate sddung dj thudng biin dp dja chin dua trin cd sd xie djnh diy mat phan xa song song vdi diy biln (Bottom simulating reflector - BSR).
Trin lit d t dja chan, BSR quan sit rat rd bang die trung mat phin xa chay song song vdi b l mit diy bien (Hinh 2 va 3) vdi hien tugng dio cue so vdi mat phan xa diy bien. BSR vdi pha sdng zero duoc phin biit cung nhCmg phan xa yeu nim tren mat BSR v i cd the quan sat duge trin mat cit pha tdc thdi. Phin tich AVO se chi ra gia trj tuyit ddi cua biin dp BSR i m ting theo
khoang each va nhan biet cac nguyen nhan gay ra di thudng bien dp nay cung nhu phan biet cac di thudng bien do bdi vi dj thuong bien dd khdng gay ra bdi khi hydrate se the hien tren ca 2 mat cat song doc va sdng ngang. Tuy nhien, viec thu no sdng ngang phifc tap hon rat nhieu so vdi sdng dge. Do dd, phuong phap phan tich AVO la mdt giai phap cd the cung cap mat c i t sdng ngang tC; so lieu sdng doc (Hinh 4).
Phuang phap phan tich AVO ra ddi nam 1984 [1]. Nghien cu^
cua Ostrander [1 ] chi ra sU tdn tai cua khi trong tang cat ket duoc phii bdi tang set se gay ra hien tugng thay ddi bien dp dia chan theo khoang each thu nd (AVO); phat hien su thay ddi bien dp nay lien quan den su suy giam ciia ty so Poisson gay ra bdi via cat ket chi)a
Hmh I.Sodoii III cac khu viic m tai gai hydrate tren toan thegidi /9/
1 4 Uhl KHi SO 4/2015
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Hinh 2. Mb doan mdt cdt dia chdn thuoc khu vtfc nUdc sdu vinh Mexico BS chay iong song vdi be mdt ddy bien [13]
Hinh 3. Trich doan mdt cat dio chdn thuoc khu vuc nudc sdu Bai Loan 8SP - mot phdn xa m cboy song song vdi be mat ddy bien [14]
Hltih 4- Sifdung phdn lich AVO dinh luang detinh todn van tdc song doc, song ngang va mdt do Cac duang cong mdu den Id md hmh trudc khi phdn tich AVO ngtfac Mdu do la md hmh sou khi dd cdp nhat Sl/dung phdn tich AVO nguac Moch dio dian mo phdng (mdu mihj sau khi phdn tich AVO ngi/ocphii hop kha tot voi vai modi
^ chdn thdc dia
khf. Shuey [2] d i chOng minh bang toin hpc thdng qua viic sir dung eie phuong trinh gan dung eua h i phUOng trinh Zceppritz rang t;/ sd Poisson l i hang so dan hdi true tiep nhat liin quan din sUphy thudc eiia he sd phin xa dja ehan (cd gdc tdi len din 30°) vio khoing cich thu no.
Phuong phap phan tfch AVO dugc tiln hanh sau khi tai lieu dja chin da dugc xd ly theo mdt ehu trinh bic toin bien do. Trong bai bio nay, nhdm tic gii se trinh biy cd sd ly thuyet ciia 2 phUdng phip phan tfch AVO va vi du ap dung trong nghien cdu khi hydrate tai khu vUe nude siu vinh Mexico vaDii Loan [13,14] cung nhU khi nang ap dung phin tich AVO trong tim kilm tham dd khi hydrate tai Viit Nam.
2. Phan tich AVO sil dung he so chan (in- tercept) v^ gradient (gradient) cOa ham so tuyen tinh
Ky thuat phin tfch AVO cho phep xie dinh dupc cac thdng sd cua da chiTa thdng qua viee phan tich sU thay doi bien do dja chan theo khoing cich thu nd. H i sd phan xa ciia sdng dan hdi dUoc md t i bing he phuong trinh phire tap Zceppritz [3]. SO dung phuong phap biln ddi tuyln tinh gan dung va chi gid lai thanh phan bae 2, Shuey [2] dua ra phuong trinh sau:
R{e) = R^+Gsin^0 Trong dd: R(9) la he sd phan xa ciia sdng dpe ed gde tdi 8
(1)
Rf.=
2 V, VIIP ] Phuong trinh (1) II tuyln tfnh khi bieu dien R(6) dudi dang ham so cua bien sin^9.
Khi do, ed the tien hanh phan tieh biin do dja ehan dUdi dang hdi quy tuyln tfnh de xae djnh he sd ehan R^ va gradient G eiia ham tuyen tinh (the hien suthay doi tai cic khoing each thu no trung gian). ThUc hien phin tich nay cho elc mach dja chan se eho kit qui l i 2 mat cat thudc tinh AVO: thupc
DiUKHl-S04/2015 15
tinh he so c h i n Rp ehinh l i mat cat cdng ciia sdng p h i n xa dpc Vp vdi gdc tcN 90°, thupc tinh gradient G ehOa dung thdng tin ve sdng p h i n xa dge VpVi ngang V^.
Gia t h i l t ring ty so Vp'^s " - *^^ ^°"9 ^^^^ t ' " ^ gradient G s i trd t h i n h :
G = R - 2R^ (2)
Trong dd, R^ A p , la he so p h i n xa cua sdng ngang cd gdc tdi 90°.
Phuong trinh (2) ed t h i v i l t dudi dang R^= (Rp- G)/2.
Rd rang, hieu sd cOa thudc tinh h i sd c h i n va gradient sau khi hieu chinh b i i n dp s i i i thude tinh t h i h i i n g i n dung mat c i t sdng p h i n xa ngang. D i l u niy cho phep sir dung phan tich AVO de d i n h gia dj thudng b i i n dp: n l u 1 dj thudng bien do xuat h i i n t r i n thudc tinh he sd chan Vp (mat d t sdng phan xa dpc) m i khdng x u l t h i i n tren mat e i t g i i sdng ngang V^ (lay thupc tinh h i so c h i n trir dt gradient) thi dj thudng bien dp n i y ed t h i l i i n quan tdi BSR.
Phuong trinh (1) duge Verm va Hilterman [4] chuyen thinh:
R (9) = R. cos- e + ^ 5 sin= 9 (3)
Trong dd: PR = : He sd phan xa Poisson;
hay:
Ao: Su thay ddi cua ty sd Poisson;
J :Ty sd Poisson trung binh.
Gil thiet a^^ = 1/3, ta ed PR^^1<T v i phuong trinh (3) trd t h i n h :
R{B) = Rp + ^-Aa-Rjsin-0 (4)
So sanh phuong trinh (1}va (4) ta ed G=^Acr-Rp Ao- = {/?^ + G ) x ^ (5) Phuong trinh (5) cho t h i y n l u lay thudc tinh h i sd
ehan edng vdi gradient s i eho k i t q u i 11 suthay doi ty sd Poisson Ao. Ty so Poisson o l i i n quan d i n - ^ , do dd 1 suthay doi ty sd Poisson ed g i i trj am se lien quan den ndc eOa via d t ket chOa khi trong khi suthay ddi ty so Poisson ed gia tri duong se l i i n quan d i n d i y cua BSR.
Ngoai ra, n l u l l y tich so cua 2 thudc tinh he sd c h i n v i gradient (RpXG)se dugc l thude tinh mdi r l t hCru h i i u
^ '
E '
/' ^
4*^
/,l^ ^SH
Hinh 5. m' cdtH(a)nCO>) 0*1
Hinh 7. mc6tR-a\r- b; bieu do quan hePvoG (c) [U]
trong viec p h i t hien cae via eat k i t ehda khi cd dp rong cao (gay ra dj thudng AVO loai 111). Cac via cat ket dang nay co ca 2 thupc tmh he sd chan va gradient vdi gia tri am Idn do do tich sdcua chiing seed gia tn duong ration
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trong khi cic via c i t khdng ehda khi s i cd bien dp yeu va tich sd {RpX G) cd gia trj Im.Thudc tfnh n i y cung eho p h i p p h i n biet cic dj thudng bien do lien quan den BSR ehda khf hydrate vcfi cac di thudng bien dp khie.
Tren bieu do R v i G t h i l t lap tir tai lieu dja ehan cho doan t u y l n dja chan AB d Hmh 5 (khu vUe nude sau D i i Loan) [14], ddi vdi mat BSR, e i hai thudc tinh R va G d i u cd g i i trj am cao. G i i trj R -i- G cung i m (Hinh 6) v i n i m t r i n gdc phan t u t h d 3 ciia bleu do (Hinh 7). Kit q u i n i y cho p h i p k i t luan cd the tdn tai tang chtfa khi hydrate doc theo mat BSR t r i n khu vUe tuyen d Hinh 4.
3. Phdn tich AVO suT dung bien dd dja chan Co sd t o i n hpe cOa phuong p h i p p h i n tich AVO tren thUc te clMc x i y diftig sO dung b i i n dp tuong ddi dudi dang he so p h i n xa hoac bien do p h i n xa da duge h i i u chlnh theo b i i n dd cua sdng tdi. Tuy nhien, viec ap dung p h i n tich AVQ dugc t i l n h i n h tren tai lieu dja ehan thu no sir dung bien do cOa mach dja c h i n (biin dd t u y i t doi).
D i l u n i y dan den mdt cau hdi k h i quan trpng: lam sao ehdng ta cd t h i n h i n dUde bien dp tugng doi trong phan tfch AVO khi chi cd t i i l i i u dja chan vdi b i i n do t u y i t doi?
Theo Smith & Gidlow [8]:
R^^^0^) = A,^^B,^
Trong dd:
a = K v i p = p ;
A = ---^sm^ 0,+ -tan^ av^ B=-4^sm^0, (7) ' 8 2 a ^ 2 a^
Hai phugng trinh (6) va (7) deu khong cd thO nguyin, chi bao gom b i i n do tuong doi.Tuy nhiin. Smith & Gidlow cho r i n g n l u b i i n dp that cua tirng mach dia chan la a^ thi sai sd binh phugng trung binh [8] se la:
K^t qu3 phan tfch hol quy binh ph Jang nh6 nhat cho a v j p [ 8 ] :
= I",C,
Trong dd:
V: Dai d i i n cho a vdp.
C: Cac trpng sd khdng cd thiT nguyin do chi bao gom tdng va tich sd cua cic b i l n khdng thiif nguyin A^ va B^ Dc dd, cAc g i i trj a^ cung khdng ed thiif nguyen, hole da dugc h i i u chinh theo bien dd sdng tdi.
Cae gia trj b i i n dp t u y i t ddi cua mach dja chan cd the dugc v i l t dudi dang Ka^ trcng dd K la h i n g so h i i u chlnh duge g i i t h i l t la khdng bilt. Do dd, phuong trinh (9) se trd t h i n h :
(10)
K^^t{Ka^)C,
Trong dd Ka^ la eae gia trj b i i n do ciia mach dja chan.
Phuong trinh (6) trd thanh:
Opp(^,) = 4
:^v]-.^f]
(11)Vdi d c dai lUgng trong ngoac duge tinh toan sCf dung p h i n tfch hdi quy.
Phuong trinh (11) eho thay, de tinh toan dUdc b i i n dp tuong ddi tir bien do dja chan, d n xae djnh dUpc gia trj cua K. Neu khdng xie djnh dugc /f thi ehi cd t h i p h i n tich AVO djnh tfnh, khdng the phan tfch AVO dinh lugng.
Phin tich AVO nguge sif dung bien dd dja c h i n khdng duge hieu chinh thee d e he sd p h i n xa se eho ket q u i khdng chfnh xae v l cac tham sd v i n toe sdng dpc, sdng ngang va mat dp.
Viec xie djnh g i i trj cua K d n p h i i t i l n hanh md phdng t i i lieu dja chan vdi nhilu khoing each thu no khac nhau sOdyng t i i lieu sonic ludng cUcTiep thee, bien do binh phuong trung binh RMS (root mean square) duge tfnh t d n chc mdi mach dia chin md phdng va h i i u chlnh vdi mach dja ehan thue dja tUOng Ong.
Be p h i n tich AVO djnh lupng n h i m nghien eOfu khi hydrate tai khu vUc nUdc siu vjnh Mexico, tO t i i lieu dja chan (Hinh 2), bien do tUOng doi dugc xae djnh (Hinh 9) dua tren d e tham so van tde sdng dpc, sdng ngang v i mat dp (Hinh 8). DUa tren k i t q u i p h i n tfch AVO ngUpc (Hinh 10), BSR duoe xae djnh la day cua ddi khf hydrate dn dinh (BGHS) ngan cieh giOa tram tieh chOa khi hydrate d ben tren v i tram tieh chOa khi t u d o d dudi.
4. Khii nang ap dung AVO trong tim ki^m tham dd khi hydrate tai khu vdc nddc sau them luc dja Viet Nam
Ngoii t i l nguyen dau kh( truyen thdng ddng vai trd het sOc quan trcng trong cdng cupc cdng nghiep hda, hien dai hda dat nUdc, d Bien Ddng ed the cdn tdn tai khf hydrate, ngudn t i i nguyen cd the bd sung cho nhiin lieu hda thach trong tUOng lai.
Cdng t i e dieu tra, tim kiem, tham dd d i u khf truyen thdng cua Viet Nam bat dau tO nhOng n i m 60 ciia the ky trUdc, nhung viee nghien edu va d i l u tra ve tiem nang khf hydrate cho den nay mdi dUge dat t h i n h "van 6e thdi sU".
DAuKHi.Sd4/2015
Tirnim 2006, Bd Til nguyin va Mdi trUcmg, Tap d o i n Dau khi Qudc gia Viit Nam da to chde hdi nghj, hdi thao v l van d l khi hydrate va d l de xuat vdi Chinh phu "Chuong trinh dieu tra, nghiin cdu tdng hgp t i l m nang khi hydrate t r i n eae viing bien va t h i m luc dja Viet Nam". Ngay 24/9/2007,
Rho Thuc dia Tong hop WinA 8. Bang dia chdn tdng hap xdy dung ti/lai lieu khu vuc nuoc sau vinh Mexico [U]
Hinh 9. Xae dmh bien do dio chdn til phan tich song dia chdn [D!
P-imoedanrp
Hinh 10. Ma! cdt phan iich AVO nguoc tir tai lieu dm chdn khu vuc nudc sdu vinh Modco 1131
1 8 ti»U6-SO A>20l 5
ThO tudng Chinh phii da quyet djnh bd sung "Chuong trltif nghiin edu, dieu tra co b i n vetiem n i n g khi hydratedcA vung bien va them luc i^a Viet Nam"vao nhiem vueOa'M i n tong the ve d i l u tra cO b i n v i q u i n ly tai nguyen - mfli trudng bien d i n nam 2010, tam nhin d i n nam 2020'[17],
Mpt sd cdng ty dau khf tai Viet Nam da xiic t i l n nghifin edu, dieu tra, danh g i i ve tiem nang khi hydrate v i bU^
dau da dua ra nhifng nhan dinh ve sU cd m i t cOa khi hydrate tai khu viic nude s i u them luc dja Viet Nam (®
500m nude) [15,16].
Hien tai, tren eO sd mang lUdi t u y l n dja ehan da phfl khap dien tieh khu vuc nUde sau t h i m lue dia Viet Nam vi vimg lan can (Hinh 10), Vien Dau khi Viet Nam dudisudil dao ciia Tap d o i n Dau khi Viet Nam dang trien khai 6i a n k h o a h g c c a p N h a n U d e "Thu thgp, phan tich, tong hgp cdc tai lieu dexdc dinh cdc ddu hieu, tien di vi tiim nang khi hydrate d cdc viing bien va them luc dja Viit Nam".
Hinh 11. So do mang ludi luyen dio chon siidung trong nghien cdu gas hydrate
F
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Hinh 12 Trich doan mat cot dia chdn tiiuockhu vi/cni/dc sau them luc dia Vilt Nam cdc ddu hieu du bdo CO kha nong ton tai gas hydrate
Dua tren k i t q u i phan tich tai lieu dja chan eung nhu p h i n tich m l u do Viin Dau khf Viet Nam thuc hien da eho p h i p du doan cd k h i n i n g tdn tai khi hydrate tren khu vuc nude siu t h i m lyc dja Viet Nam. Trin mpt sd lat cat dia chan qua khu vUe nghiin cOu (Hinh 11}, sU xuat hien be mat p h i n xa manh, l i i n tyc chay song song vdi mat d i y bien eiing cac dOi p h i n xa trang, eae ddi khf t u dc, d c dj thudng b i i n dp cd the l i i n quan tdi khi hydrate.
TO ngudn tai lieu dja chan vdi cic d i u hieu tdn tai khi hydrate, ket hgp vdi eae tai lieu dja chat l i i n quan khac, ed the tien hanh phan tieh dac b i i t cic thudc tinh dia chan, d i e biet l i phan tieh AVO n h i m n g h i i n cOu d u b i o su p h i n bd cOa BSR n h i m tim kiem khi hydrate tai khu v\ic nudc s i u them lyc dia Viet Nam.
5. Ket luan
TO k i t qua i p dyng p h i n tfch AVO trcng nghiin cOu khi hydrate, nhdm t i e g i i rut ra mot so ket l u i n sau:
K i t q u i phan tfch AVO chi ra rang g i i tri tuyet doi cua b i i n dp BSR I m tang thee khoing d c h v i BSR dUOe xae djnh l i day cOa ddi khi hydrate on dinh (BGHS) ngan cieh giOa tram tieh chOa khi hydrate d b i n t r i n v i tram tieh chu'a khf t i i do d dudi.
Dya t r i n cac ket q u i nghien cOu cOa de tai khoa hpe d p Nha nude "Thu thap, phan tfch, tong hgp d c tai lieu de xae djnh cic d i u h i i u tien de ve tiem n i n g khi hydrate d eac vung b i l n va t h i m luc dja V i i t Nam", tren khu vUe nude sau thudc t h i m luc dja Viet Nam, tO nguon co sd dO lieu h i i n cd, cd t h i tien h i n h p h i n tich AVO d l nghien CUXJ d u bao sU p h i n bo cua BSR nham tim kiem khi hydrate.
Till lieu tham khio
I. WJ.Ostrander. Plane-wave reflection coefficients for gas sands at non-normal angles of incidence. Geophysics. 1984; 49(10):
p. 1637-1648.
£. R.T.Shuey. A simplification of the Zoeppntz equations. Geophysics. 1985; 50(4): p. 609 - 614.
3. K.Aki, P.G.Richards. Quantitative Seismology: Theory and methods. Freeman. 1980.
-T. Richard Verm, Fred Hilterman. Lithology color-coded seismic sections: The calibration of AVO crossplotting to rock properties. The Leading Edge.l995;14(8): p. 847-853.
5. Steven R.Rutherford, Robert H.Williams.
Amplitude-versus-offset variations in gas sands.
Geophysics. 1989; 54(6): p. 680 - 688.
6. John PCastagna, Steven W.Smith.
Comparison of AVO indicators: A modeling study.
Geophysics. 1994; 59(12): p. 1849-1855.
7. John P.Castagna, Herbert W.Swan.
Principles of AVO crossplotting. The Leading Edge.
1997; 16: p. 337-342.
8. G.C.Smith, PM.Gidlcw/. Weighted stacking for rock property estimation and detection of gas.
Geophysical Prospecting. 1987; 35: p. 993 -1014.
9. Michael D. Max. Natural gas hydrate in oceanic and permafrost environments. Kluw/er Academic Publisher. 2003.
10. Takashi Uchida. Methane hydrate: A future energy resource?. Technology Research Center. Japan Oil, Gas and Metals National Corporation. 2004.
11. Michael D.Max, Arthur HJohnson, Vl/illiam RDillon. Economic geology of natural gas hydrate. Published by Springer. 2006.
12. P.Wang et al. Initial Reports. Proceedings of the Ocean Drilling Program. 2000.
13. Dianna Shelander, Jianehun Dai, George Bunge, Dan McConnel, Niranjan Banik.
Predicting gas hydrates using prestack seismic data in deepwater Gulf of Mexico. AAPG Geoscience TeehnologyWcrkshcp, Houston,Texas. 16 March, 2010.
14. Hui Deng, Pin Yan, Hailing Liu, Wenzao Luo. Seismic data processing and the characterization of gas hydrate bearing zone offshore of Southvi/estern Taiwan. Terrestrial Atmospheric and Oceanic Sciences. 2006; 17(4):
p. 781 - 797.
DAUKHf-S04/ 19
15. VGP.Seiimic data processing and inteipretation of 17. Thu tacmg a i n h phu. Quyet ffin/i wV do su, Block n9-U2omhoreVietnam.20m. Chuang trinlinghienalu, aOu ttacabanvltOmndngft hydrate dcdc viing bien va them luc dia Viet Nam vao nivm 16. VGP. Complex marine geologi^geophysKal ^ ^^.g^ ^„,^„g ^4 f^„^,a ban va quan If tai nguyi, exphtation of gas hydrate accumulations offshore Vietnam. -^. ^ ^ ^..^ ^^ ^^ ^^^ ^.^ ^^.^ ^.^ ^.^ ^^
2011 Quyet dinh so 1270/Q€)-TTg. 24/9/2007.
AVO analysis in gas hydrate exploration and the possibility of its application in deep water continental shelf of Vietnam
Nguyen Thu Huyen, Nguyen Trung Hieu, Tong Duy Cuong Nguyen Manh Hung, Nguyen Danh Lam, Trinh Xuan OMOI Vietnam Petroleum Institute
Summary
AVO, which stands for Amplitude Variation with Offset - or more simply. Amplitude Venus Offset, is a seisnk technique that looks for direct hydrocarbon indicators using amplitudes of prestack seismic data. The AVO technique beatme very popular in tite petroleum industry, as one could physically explain the seismic amplitudes in ternu ttf rock properties. For example, bright-spot anomalies (he. the high amplitude reflections seen on the P-wave stadW section) could be investigated before stack to see if they also had AVO anomalies. It can help us distinguish the geo- logical objects that created bright-spot anomalies, such as gas-bearing sandstones, coal seams or volcanoes.
AVO analysis proved successful in certain areas of the worid for gas hydrate exploration but has not been appM in Vietnam. In this paper, the authors describe AVO analysis m&hods and some examples of using AVO in gas hydnOt exploration in the worid as well as the possibility to apply it in deep wafer areos on the continental shelf of Vietnam, Key Vfords: Gas hydrate. AVO, deep water area.