Sử dụng phương pháp phân tích avo trong tìm kiếm thăm dò khí hydrate và khả năng áp dụng tại việt nam

THAM DO - KHAI THAC DAU KHI ]SIJ DUNG PHUONG PHAP 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 Hieu, ThS Tong Duy Ci/oig KS N g u y i n Manh Hiing, KS N g u y i n Danh Lam, TS Trinh Xuan Cirimg Vien Ddu Viet Nam Email- huyennl^vpi.pvn.vn Tdm tat PhddngphdpphdntichAVO(AmplitudeVariationswithOffsethayAmplitudeversusOffsetjldphdongphdpth kiimtrifctiepcdcbaychifaddukhidifatrenkythudtphdntichbienddcuatailieudiachdntrifdckhicdng.AVOdU^ sddung ph6 bien cdng tdc tim kiem, thdm dd nhd khd ndng lien ket biin dja chdn vdi ddc tinh cua dd chUa Cdcdithifdngbiendd(phdnxadiachdncdbiinddcaotrinmgtcdtdiachans6ngdpc)cotheduacngh.encUutnfdt khicdngdixemc6ditbddngAV0haykhdng?BiiundygiiJpphdnbietcdcdditddngdfachat(catketchifakhi,than At hay dd nui Ida) dd gdy di thifdng biin Phifong phdp AVO dddc dp dung cdng tim kiem gas hydrate tren the gidi nhifng chiia dugc dp dung dViitNam.Trongbdibdondy,nhdmtdcgidgidithieucasdtythuyetcuaphifangphdpphdntichAVOvdviduveket qud sd dung AVO 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 khoang each va nhan biet cac nguyen nhan gay di thudng bien dp cung nhu phan biet cac di thudng bien bdi vi dj thuong Cic cdng tie nghien cCfu, dilu tra cd ban v l tiem nang 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 vi tdn tai d eie khu vuc ed siu nUde bien Idn (Hinh 1), ndi cd it gieng khoan tim kilm tham ma hau nhuchi cd cac ludi tuyln dia chin Do viy, de dilu tra, tim kilm, thim dd hydrate, phin tich tai lieu dia ehan se cho phep du bao sU ton tai cic ddi chijra hydrate Phuong phip du bao eae ddi chura 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 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 vi cd the quan sat duge trin mat cit pha tdc thdi Phin tich AVO se chi gia trj tuyit ddi cua biin dp BSR i m ting theo 14 Uhl KHi SO 4/2015 bien dd khdng gay bdi hydrate se the hien tren ca 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 ddi nam 1984 [1] Nghien cu^ cua Ostrander [1 ] chi sU tdn tai cua tang cat ket duoc phii bdi tang set se gay hien tugng thay ddi bien dp dia chan theo khoang each thu nd (AVO); phat hien su thay ddi bien dp lien quan den su suy giam ciia ty so Poisson gay bdi via cat ket chi)a Hmh I.Sodoii III cac khu viic m tai gai hydrate tren toan thegidi /9/ PETROVIETNAM 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 li 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 tai lieu dja chin da dugc xd ly theo mdt ehu trinh bic toin bien Trong bai bio nay, nhdm tic gii se trinh biy cd sd ly thuyet ciia phUdng phip phan tfch Hinh Mb doan mdt cdt dia chdn thuoc khu vtfc nUdc sdu vinh Mexico BS chay iong song vdi be mdt ddy bien [13] AVO va vi du ap dung nghien cdu hydrate tai khu vUe nude siu vinh Mexico vaDii Loan [13,14] cung nhU nang ap dung phin tich AVO tim kilm tham dd hydrate tai Viit Nam Phan tich AVO sil dung he so chan (intercept) 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 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 phan bae 2, Shuey [2] dua phuong trinh sau: Hinh 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] R{e) = R^+Gsin^0 (1) Trong dd: R(9) la he sd phan xa ciia sdng dpe ed gde tdi Rf.= V, VIIP ] Phuong trinh (1) II tuyln tfnh bieu dien R(6) dudi dang ham so cua bien sin^9 Khi do, ed the tien hanh phan tieh biin 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 Hltih 4- Sifdung phdn lich AVO dinh luang detinh todn van tdc song doc, song ngang va mdt Cac duang cong mdu den Id md hmh trudc phdn tich AVO ngtfac Mdu la md hmh sou dd cdp nhat Sl/dung phdn tich AVO nguac Moch dio dian mo phdng (mdu mihj sau phdn tich AVO ngi/ocphii hop kha tot voi vai modi ^ chdn thdc dia khoing each thu no trung gian) ThUc hien phin tich cho elc mach dja chan se eho kit qui li mat cat thudc tinh AVO: thupc DiUKHl-S04/2015 15 THAM DO - KHAI THAC DAU KHl tinh he so chin 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) Ap, la he so p h i n xa cua Trong dd, R^ ^ ' E ' /' 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 chin va gradient sau 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 dj thudng bien 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 eit g i i sdng ngang V^ (lay thupc tinh h i so chin trir dt gradient) thi dj thudng bien dp n i y ed t h i liin quan tdi BSR ^ 4*^ ^SH /,l^ Hinh m' cdtH(a)nCO>) 0*1 Phuong trinh (1) duge Verm va Hilterman [4] chuyen thinh: R (9) = R cos- e + ^ sin= Trong dd: PR = (3) : He sd phan xa Poisson; Ao: Su thay ddi cua ty sd Poisson; J :Ty sd Poisson trung binh Gil thiet a^^ = 1/3, ta ed PR^^1