PETROVIETNAM L/NG DUNG HIEU UNG HAP THU VA TAN SAC TOC OO SONG 0!A CHAN VAO TIM KIEM, THAM DO VA KHAI THAC DAU KHI TSKH Truomg Minh Hgi Ddu khi Viet Nam Tdm t i t Phdn tich ddc trUng ddng lUc vd ddng[.]
PETROVIETNAM L/NG DUNG HIEU UNG HAP THU VA TAN SAC TOC OO SONG 0!A CHAN VAO TIM KIEM, THAM DO VA KHAI THAC DAU KHI TSKH Truomg Minh Hgi Ddu Viet Nam Tdm t i t Phdn tich ddc trUng ddng lUc vd ddng hinh sdng dia chdn Id mdt nhdng cdsdquan trpng di nghiin cdu m trudng dia chdt, dUbdo thdnh phdn thgch hpc chdt lUu vd ddc diem chda Cdc thdng sdhdp thu dUdc sddung nhu c chi thi ddu Tinh chdt mdi trUdng ddn hdi khdng ly tUdng dUac dng dung thdm dd ddu khidi gidi quyit cdc nhiim vu: ddng nhdt hda cdc via ddu cdc giing khoan ddu theo tdi liiu tuyin dia chdn thdng ddng (vertical seismic profile - VSP) vd siiu dm; dUbdo vd phdt hiin cdc tdng ddu theo tdi liiu dia chdn trin mat; gidm sdt cdc via ddu kbi qud trinh khai thdc; kiem tra cdc kho tdng trd ngam dudi ddt; tdng hi sdthu hdi ddu Phuang phdp hdp thu vd tdn sdc tdc dp sdng (absorption and velocity dispersion -AVD) dd duac thd nghiim dmd Bgch Hd, Dgi Hung vd mdt sdkhu vUc khdc dUa trin tdi liiu dia cbdn 2D, 3D Ket qud cho thdy, phddng phdp ndy khd hiiu qud, giup khang dinh cdc via ddu dd cd vd phdt hiin cdc di thudng khdc dmdt sd via ddu mdi Do dd, cdn tiip tuc day mgnh viic Ung dung phuang phdp hdp thu vd tdn sdc tdc dp sdng dia chdn tim kiim, thdm dd vd khai thdc ddu kbi d Viet Nam nhdm mdrdng khu vUc dang khai thdc, tim kiim cdc ddi tUdng mdi, gia tdng trdlUdng ddu kbi vdi chi phi thdp nhdt Gidi thieu Thim dd dja chan la phuong phap rat hieu qua de nghidn eUu eau true dia chat va cac tinh chat die trUng cua mdi trudng truyen sdng.Tuy nhidn, vide nghien cUu tinh chat mdi trudng cdn gap nhieu khd khan mdi trUdng dia chat thue te phUe tap va khac xa vdi md hinh dan hdi ly tudng da SLf dung de tinh toin ly thuyet Do dd, nghien cUu tinh chat mdi trudng dan hdi khdng ly tudng se bd sung hoan thien md hinh dja cha'n gan vdi mdi trUdng thuc te hon Nhieu nudc tren the gidi d i sif dung phdi hpp cac die trUng dpng lue eua sdng (bidn dd, phd tan sd) va cac die trUng ddng hpc (thdi gian va tde dp) de nghien cUu phan thach hpc, tudng mdi trUdng, dU bio di thudng ap suit, nghien cCru die diem ehufa va dU bao ehat lUu (dau, khQ Trong bai bao nay, tie gii gidi thidu ket qua nghien eUu ve ning mdi eua phuong phap hap thu va t i n sac tdc dd sdng dja chan va vide Cfng dung hudng nghien cUu niy tim kiem, tham dd dau d Viet Nam thdi gian g i n day Die trUng t i n sic tdc sdng dia chan mdi trUdng chiira dIu 2.7 ca che hdp thu ndng luang vd tdn sdc tdc dp sdng dia chdn cdc tdng chda ddu Anh hudng cua tinh chit v i t ly va trang thai pha (khi, Idng) cua chat lUu den co che tieu tan nang lupng sdng la mdt nhUng van de chua dupe nghien cUu day du phan tich die trUng hap thu sdng dja ehan Theo tinh toan ly thuyet ve hap thu sdng, mdt sd nghien eUu mdi day eho rang sU tdn tai chat lUu khdng gian rdng va cac bpt khien tinh chat hap thu sdng tang manh, lam thay ddi die trUng hap thu phu thudc vao tan sd Oieu cd the lien quan den eie qua trinh xay ban than chat lUu SU bien ddi trang thai pha cua dau chUa via lam thay ddi dp cUng am hpc, do lam tang he sd hap thu nang luong va xuat hien sU tan sac tdc dd sdng dai tan sd eao Ket qua tinh toin va thife nghiem cho thay sU thay ddi he sd hap thu va tdc dp sdng mdi trudng dau deu phu thudc vao tan sd, die biet sif thay ddi tdc dp ty Id thuan vdi can bac II cua tan sd Khac vdi dau khi, nude cd trang thai pha, vay eo che trao ddi vat chat khdng xay ben ngoai via dau ma chi cd the xay d chieu sau rat Idn hoac gan ngudn thuy nhidt; khdng phu thude vao eo ehe tidu tan nang lupng dia ehan, su gia ting dp hap thu phai di ddi vdi sU tan sac tdc dd pha sdng Oieu xuat phat tU nguyen ly co ban cua md hinh mdi trUdng dan hdi khdng ly tudng Tuy nhien, nghien eUu thim dd dja chan hidn ehua cd cdng trinh nao de cap den su tan sac tde dp sdng dai tan sd thap iUWi-so 4/2013 17 THAM DO - KHAI THAC DAU KHI 2.2 Di thudng hdp tbu vd tdn sdc tde dp sdng dja ehdn Id cdc chi thj ddu kbi Theo kit qui nghidn eUu eo ehe hap thu sdng, sU thay ddi eie tham sd vit ly eua chat Idng trang thai can bde hoi khien dp ehju nen ting manh, giam dd dan nhiet va sUe cing be mitTU dd, dan den ting dp hap thu sdng tan sd thap, cd su tic ddng qua lai giUa dp nhdt quan tinh, dp din hdi nhidt cua chat luu v i dat d i xung quanh Cac qui trinh bien ddi chat luu l i khdng tuyen tinh, dp hip thu cao lim t i n sic tde dp truyen sdng Khi thay ddi trang thii pha, hidn tuong trao ddi vit chat giUa eie pha xiy lam t i n sie tdc dd ding ke v i dp hap thu ting eao hon so vdi dd hap thu eua bin thin chat luu trang thii binh thudng Cie nhi dja v i t ly Hpc vidn Dau Gubkin (Lien bang Nga) d i nghien cUu, thCf nghidm co che hap thu sdng v i thiy ring eie via dau phin bidt vdi mdi trUdng xung quanh bdi dj thudng hap thu eao, hieu Ung t i n sie tde dp sdng phu thude vio t i n sd dia ehan (tan sd thap) Theo kit qui thue nghidm, mUe dd hap thu sdng dpe cic via chUa dau cao hon nhieu so vdi tinh toin ly thuyet [1, 3] Khi phin tich sd lieu tuyen dja ehan thing dUng, da phit hidn dd t i n sic tdc dd duong +5% (ting theo tan sd) dii t i n sdIO - 70Hz tai nhieu gieng khoan cd sin phim diu Vi viy, eie dj thudng hap thu v i t i n sie tde dd sdng dja chan d i trd eie chi thj quan ve sif tdn tai cua via dau Phuong phip nghien cihi tinh chat hap thu va tin sic tdc sdng dja chan 3.1 XCfly AVD trin tdi lieu dia cbdn phdn xg 3.1.1 Xae dinh gia sdhdp thu (absorption decrement) Odi vdi mdi trUdng phin Idp mdng, gia sd hap thu phu thudc vio tan sd ed the tinh theo edng thdc: ,n^'^^) Trong do: Ix/xAt (hoae via diu khQ da phin ehua dUOc xie djnh, trU trUdng hop da cd gieng khoan phit hidn dau Do viy, van d l d i t la chpn At de t, va t^ nim can trdn v i can dUdi cua tang nghidn cUu Ben canh dd, hieu qui tinh toin phu thupc nhieu vao hieu biet dia chit, kinh nghiem chpn thdng sd cua ngUdi xd ly va phuong phip tinh phd S(f) eua sdng dja ehan (phd bidn dp, phd log) Vide xie djnh gia sd hap thu 5(f) dupe thUe hien tren mach ghi don hoic mach edng diem siu ehung 2D v i 3D, dpe theo thdi gian quan sit hoic theo tUng ddi tuong ed trien vpng diu Kit q u i xU ly bing phan mem AVD cho mat eat dj thudng hap thu theo tuyen quan sit 3.1.2 Xde dinh tdn sdc tde sdng (velocity dispersion) Do t i n sic tdc dd sdng dupe xie dinh bing cieh thifc hien theo cic ehu trinh ehuan de phin tieh tde dp Cic bing ghi nguydn thuy dupc sip xip theo trit tudiem siu ehung, dupe Ipe qua eie dii tan hep (15 - 25, 20 - 30,25 35, 30 - 40, 34 - 45,40 - 50,45 - 55 Hz), sau dd dUa vio xil ly.Trdn mdi dii tan, tien hinh xie djnh phd tdc dp ngang tren eie diem quan sit Cie gii trj tdc dp diem siu chung thu dupe trdn cic tan sd khie dupe the hidn tren mdt bieu dd tdc dp V(f) phu thudc vio tan sd f v i xie dinh dp t i n sic tde dp bang gii trj dv = Av/V (%) Can luu y ring, qui trinh phin tieh dp t i n sic tdc d^ sdng rat phUc tap, mit nhieu thdi gian, viy chl ndn thuc hien trdn khu vifc cd dj thudng hap thu, de ning eao dp tin ciy eua phuong phip AVD 3.2 Xdly AVD tren tdi lieu tuyen dia chdn thing ddng Tinh chat hap thu v i t i n sic tde dp sdng dja chin Idng gieng khoan cd the dupe nghidn eUu bing tii lieu tuyen dja chan thing dUng Quan sit sdng dia chin gieng khoan thuan loi hon trdn be mat, trinh difOC inh hudng eua eie loai nhieu: nhieu tan sd cao; dieu ki^n thu phat khdng ddng nhat; giao thoa sdng, sdng phin x? nhieu lan mdi trudng phin Idp; Inh hudng phin ky va khue xa Phuong phap xic dinh gia sd hip thu v i dd t i n sic tdc dp sdng dia chin giing khoan duoc thife hidn theo cic budc sau: 5(f) l i gia sd hap thu; W,(f) v i Wj(f) l i phd ning luong dupe tinh d cisa sd m i tam l i thdi diem t, va t^, cich mdt khoing At = t j - t , Theo cdng thUc, vide xae djnh gia sd hap thu 5(f) kha de dang Tuy nhidn, trdn thife te ehieu day tang hap thu Bing ghi tuyin dja chin thing ddng duoc tiln hanh Ipe vdi cac dii t i n sd hep khie (nhu xCr i) dia chin tren mat) d l dua vao xU ly Chpn cifa sd AH = H, - Hj thich hpp 6i xie dinh gia sd hip thu theo cdng thurc: PETROVIETNAM 'y(/) = \n\S„M-ln\S„,{f} fxAH xV Trong dd, S„(f) l i phd ning luong tai ehieu sau H Bing cich truot lidn tuc cCfa sd AH tUtrdn xudng dudi se thu duoe g i i trj biln thien eua gia sd hap thu 6(f) dpe theo gieng khoan Dd t i n sle tde dp dv(f) dupe xic dinh ddng thdi cifa sd AH trupft theo ehieu siu Tai mdi khoing AH, tde dp trung binh eua eie d i i tan sd khae Trdn bieu dd dv(H) the hidn sU bien thien v i t i n sac tde dd theo ehieu siu, qua dd se xie dinh di thudng t i n sac tde da Ket qui xic djnh 6(f) va dv(f) duoc bleu dien trdn hd tpa dp thdng nhit theo chieu siu H sd l i co sd quan trpng de minh giii v i phit hidn cie dj thudng hip thu ed lidn quan den tang sin phim l7ng dung hieu liTng hap thu va tan sic tdc sdng dia chin nginh d i u khf v i thay ddi thinh phin thach hpe Ngoii ra, vide phin tieh tdng hop ket qui xU ly tai lieu dja ehan theo AVD va AVO (amplitude versus offset) edn md ning phin bidt duoe loai ehat lUu (dau hay khQ, bdi vi dj thudng AVD ehi thj SLf hidn dien cua dau va khi, edn di thudng AVO phit hidn vung bio hda khL 4.3 Gidm sdt tinh trgng md ddu bdng dia chdn (seismic monitoring) Nhiem vu giim sit dja chin md dau dang khai thac la rat can thiet sd luong gieng khoan giim sit cdn it Khi ning xie djnh ranh gidi via sin pham bing AVD ed the Ung dung de giam sit sU thay ddi via qui trinh khai thae Trong trUdng hpp nay, tat ei eac dieu kidn dia chat md van giQ nguydn va chi ed via diu thay ddi khai thic Do dd, vide xac djnh eie thdng sd hap thu 6(f), dv(f) eho phep nghidn eUu sifthay ddi tinh trang md qua thdi gian khai thae Cdng tic giam sat dia chan dupe thue hidn bing each quan sit dja ehan 40 lip lai mdt thdi gian nha't dmh 4.1 DUbdo cdc md ddu Trong giai doan tim kiem, chUa cd eie gieng khoan, trdn eO sd xU ly v i phin tieh dia ehan cie dj thudng hap thu v i t i n sie tde 66 6\jgc phat hidn bing phuong phip AVD ed the ehi eac khu vifc ed trien vpng tieh tu dau va loai trU eae eau tao (hoae bay) khdng cd trien vpng Trong q u i trinh minh giai sd lieu AVD, cin SLf dung them eac t i i lieu dja chit - dja vat ly khic nhim ting dd tin cay eua kd't q u i minh giai Vide SLf dung phuong phap AVD giai doan se ning cao hidu q u i kinh te - ky thuit eua cdng tie tim kiem dau 4.4 Kiem tra cdc kho tdng trd ngdm bdng AVD Qui trinh tUOng tu qui trinh giim sit md 4.5 Tdng hi sd thu hdi ddu Trang thii pha eua chat lUu (khi - Idng) tao ndn dj thudng hap thu sdng dja chan Tren thuc te, trang thii niy khdng on djnh va chiu tic ddng eua sdng dia chin rat Idn, dudi ap life eua sdng khdi (sdng dpe) trang thii eua dau se tang dp ket hpp va chuyen tU pha sang pha Idng (dau) Sd dung hidu Ung cd the giup tang sin luong dau d the Idng, dd lam ting lupng dau thu hdi d cae md khai thie den giai doan cudi 4.2 Thdm dd vd thdm dd mdrdng cdc md ddu Mot sd ket q u i ap dung phUOng phap AVD d Viet Trong giai doan thim dd, trdn md d i ed eie gieng khoan phit hidn dau khi, vide sCf dung phuong phip AVD de lidn kit v i ddng nhit cic via sin pham, xic dmh ranh gidi md (contour) rat can thilt v i se dem lai hieu qua cao Tii lidu tuyin dja chan thing dUng (VSP) eho phep lidn ket mdt cieh tuong ddi chinh xie eie di thudng hap thu vdi cic via sin pham Phdp so sinh ehuan hda sd lieu AVD vdi cie sd lieu thCf via cie gieng khoan trdn eung dien tieh hoae khu VLfc lln cin cho phdp xic dinh v i chlnh xac ranh gidi via sin phim Khdng phu thude vio dang bay (eau tao hay phi elu tao), phuong phip niy giup ting ty Id cdng cua cdng tic khoan thim dd Trong trudng hpp nay, se trinh dUOc inh hudng sai sd xiy dung bin dd ciu tao Nam Phuong phip AVD da dUoe sCf dung tim kilm, thim dd dau va eho cie kit qui rat kha quan d Tiy Siberia (Lien bang Nga), Trung Qudc, Nam My, vung bien Ba rent Trong bii bio nay, tie gii ehi gidi thidu mdt sd ket qui ban dau eua vide i p dung phUdng phip AVD tim kiem, thim dd diu d Viet Nam Phuong phip AVD da dupe thif nghidm d eie be tram tieh Sdng Hdng, Cdu Long v i Nam Cdn Son vdi cic dieu kidn dia ehat khie vdi mue dieh i p dung thCf nghidm mdt sd tuyen dia ehan 2D, 3D v i t i i lidu tuyen dja chan thing dUng d i dupe lifa ehpn de xU ly theo phan mem AVD THAM DO - KHAI THAC DAU KHI 5.7 Nghiin cdu AVD trin tdi lieu dja chdn phdn xg - 1.800ms) nam d phia Tiy Nam ciu tao trim tich Miocen trung Quan sit tren mat cit dia chin ed sif xim tan tU dudi ldn trdn 5.1.1 Tuyin A (biCdu Long) Tuyen A eit ngang qua md Bach Hd va qua eae gieng khai thie dau (420, BT-2, 417) ket qua xU ly ed phit hidn cie dj thudng hip thu (Hinh 1) Dj thudng Al (1.1) (x = 141 - 280; t = 2.100 - 2.300ms), ed kha ning lidn quan den cic via dau d i dupe phit hidn tang Miocen ha, nam ke i p trdn mdng Can luu y, tai gieng khoan 112-BT-1X chi phit hidn ddgc mdt sd dj thudng nhd nam d cinh Tay Bic v i Odng Nam, ed the lien quan den tram tieh Oligocen phu trdn he trUde Kainozoi Oieu dd ed the giii thieh vi gieng 112-BT-1X khoan trung ndc elu tao nhUng khdng gap ddi tupng chUa dau Di thudng A2 (1.2) (x = 421 - 505; t = 3.000 - 3.300ms) ed bidn dp cao, kich thude Idn, xet ve vi tri va ehieu siu cd the lidn quan den eie tieh tu dau tram tieh Oligocen d cinh sut phia Odng eau tao Bach Hd Tuy nhien, neu lien ket vdi tuyen song song d phia Bie (T A1309 3D va T 0402024) d thdi gian 3.000 - 3.200ms va gieng khoan 1107, noi ed via dau, thi diy l i phan keo dai eua via dau cinh Odng eua md 5.1.3 Tuyin CvdD (biNam Con Son) Cae tuyen C va D eit qua md Oai Hiing thudc be tram tich Nam Cdn Son dupe ehpn de xif ly AVD toin didn hon, sd dung cae phan mem xU ly hap thu va tan sle tde dp trdn t i l lieu dia ehan 3D trdn mat va tai lieu tuyen dia ehan thing difng (cic gieng 1X, 3X, 4X v i 8X) Gia sd hap thu dUOe xic djnh theo phuong phip so sinh phd va md hinh hda (so sanh md hinh ly thuyet va thife nghidm nham dat dp tuong Ung tdi da vdi sd lieu thUe te) SU hidn didn cae giing khoan lam ehuan d i eho phep ehpn eae thdng sd xCf ly tdi UU de giii quyet nhidm vu phit hidn tang sin pham 5.1.2 Tuyin B (biSdng Hong) Tuyin eit eit qua eau tao Bach Tri v i gieng khoan 112-BT-1X tdn tai mdt sd dj thudng hap thu, dd eie phit hidn dj thudng ding ehu y hon ca (Hinh 2) Di thudng Bl (2.1) (x = 11.421 - 11.605; t = 1.800 2.200ms) trim tich Miocen trung Di thudng B2 (2.2) (x = 1.1060 - 1.1160, t = 1.700 Trdn tuyen C phat hidn kha nhieu dj thudng hap thu (Hinh 3) dd ed dj thudng ding lUu y: Dj thudng Cl (3.1) (X-470-590; t = 2.200-2.400ms, tuong duong 2.900 - 3.100m) Sd lieu tinh gia sd hip thu bing t i i lieu tuyen dia chan thing dUng d " t ;