Hoi nghj KHCN 2000 "Nganh Dau khi Viet Nam trffdc them theky 21'''' KINH NGHIEM TL/ NGHIEN CCfU VIA, D A N H GlA TRQ LLTONG DAU KHI VONG TAY NAM VIET NAM Vd Van Minh Unocal TOM TAT Xac dmh lugng the tich[.]
Hoi nghj KHCN 2000 "Nganh Dau Viet Nam trffdc them theky 21' KINH NGHIEM TL/ NGHIEN CCfU VIA, D A N H GlA TRQ LLTONG DAU KHI VONG T A Y NAM VIET NAM Vd Van Minh Unocal TOM TAT Xac dmh lugng the tich diu cd the khai thae (trff lugng thu hdi) vdi tin cay cao ludn la bai toan khd dugc dat eho cac ky su diu Chi thdng tin dugc cung cap mdt each chinh xac viee xay dung ke hoaeh phat then md mdi that su hgp iy va hieu qua Bai viet trinh bay phuang phap luan xac suit thdng ke vdi tin cay cao nhim phan tieh xay dung hinh anh trung thuc cua cac thdng sd dac trung ciia mot vung md Viec ffng dung cdng phuong phap luan vao viec danh gia tru tugng md thude khu vue phia Tay Nam Viet Nam se thay cho Idi ket luan ve kha nang ffng dung hieu qua cua phuang phap a Viet Nam, nhit la cho nhung vUng ma thdng tin mdi trudng dia chat la cd sin GIOI THIEU Trong nhieu nam qua, cdng nghiep dau da ddng vai trd rat quan trgng dd'i vdi su tang trudng kinh te ciia Viet Nam Tuy nhien, viec khai thae mdt md dau khdng phai dan gian bdi vi chi phi dau tu ban dau rat ldn Se that su rui ro dau tu hang tram trieu dd la xay dung ca sd tang de khai thae giai doan ban dau nay, khd ed the hieu biet can ke ve viing md dau khf se khai thae Cau hdi dat la trude dau tu khai thae mdt md dau khi, lieu ngudn tai nguyen dau khf tim dugc ed tru lugng dii Idn de khai thae kinh te hay khdng? Tru lugng thu hdi dau duge djnh nghTa la the tfeh dau khf cd the khai thae dugc td mdt viing mo nhat djnh Oe cd the' tfnh toan trd lugng nay, cd rat nhieu phuang phap va quy trinh tinh toan lien quan den nhieu ly thuyet khac chuyen nganh ky thuat via ed the duge tdm tat nhu Bang Viee sd dung mdt quy trinh thieh hgp phu thude vao cac dieu kien eu the tung viing Bang 1: Cae phuang phap thudng gap danh gia trd lugng Phu'dng phap Pham vi ffng dung Giai doan tot nhat So lieu yeu cau The tfeh Tat ca eac giai doan Giai doan tham dd Thd'ng ke/kinh nghiem Can bang vat chat Tat ea eac giai doan Khai thae Rat nhieu va tdng hgp Md phdng via Tat ea eac giai doan Khai thae Rat nhieu va tdng hgp Khai thae Khai thae Khai thae Dudng khai thae suy giam giai doan tham dd va tim kiem, phuang phap the' tfeh la thfch hgp nhat de sd dung Cdng thde toan hgc eiia phuang phap duge trinh bay d phuang trinh va Nhu vay, neu mdi trudng chiing ta quan tam cd tiem nang ve khi, cae thdng sd dae trung chinh eiia md khf la: dien tfeh viing ehda dau khf A (m^), be day tang ehda h (m), rdng tang ehda if (%), bao hda nude Sw (%), he sd gian nd khf Eg va he sd thu hdi RF (%) L/u diem cdng thde la rat dan gian nhung yeu cau phai xac djnh mdt each djnh lugng cac thdng sd dae trung eiia via Trulugngmdkhi = A h ( | ) ( - S w ) E g R F 12 (1) Hoi nghj KHCN 2000 "Nganh Dau VietNam trifdc them theky 21' Trulugngmddau = A h ^ ( - S g - S w ) R F / B o • • (2) Dan vj sddung bd = 0,3048 met; bg khdi = 0,02831685 met khdi km = 1000 met; ti=10^ , _ ^ 7'" Cae djnh nghTa va thuat ngd A = Dien tfeh cua mdt viing tfeh tu dau khf dudi ldng dat, duge xae djnh bang phuang phap dja chan chieu Eg = He sd gian nd khf = ti le the tfeh eiia khdi khf tai dieu kien vi'a va the tfeh ciia cung khdi khf dd nhung d dieu kien ehuan (1 at mdt phe, 15°C) Bo = He sd the tfeh dau via = ti le the tfeh eiia lugng dau tai dieu kien ehuan (1 at mdt phe, 15°C) va the' tfeh ciia cung lugng dau dd tai dieu kien via RF = He sd thu hdi dau (khf) = la phan tram lugng the tieh dau (khi) cd the thu dugc theo dieu kien ap i dung cua cdng nghe va kinh te ed sin cua khu vue Tuy nhien, viec djnh lugng cac thdng sd tren that su la mdt van de khdng dan gian Khdng phai lue nao, d giai doan tim kiem, tham dd eung deu ed sin cae thdng sd tren Ve mat ehuyen mdn, ed the nhieu thdng tin cua vung dang khao sat la ed sin, vf du nhu ke't qua cdng tac khao sat dja chat, ke't qua viee xd ly va minh giai cac tuyen dia chan, thdng tin khao edu dja vat ly gie'ng khoan hoae mdt vai thdng tin lien quan de'n viec thd gie'ng va khai thae ban dau Nhung tide rang cae thdng tin tren chua the eung cap djnh lugng chfnh xac cae thdng sd yeu eau eho viec tfnh toan tru lugng Ke't qua la, viee phan tfeh danh gia trd lugng dau khf ludn tdn tai mdt mdc sai sd nha't djnh ma mdc sai sd Idn hay nhd phu thude vao su hieu biet ve mdi trudng dja chat dang khao sat, dac biet la cac thdng sd dac trung ehfnh cua nd PHU'ONG PHAP MO PHONG MONTE CARLO Danh gia tru lugng bang md hinh tien djnh nghTa la dung mdt md hinh danh gia vdi cac bie'n sd dugc cung cap bdi mdt gia trj la hang sd xac djnh Vdi edng thue tinh trd lugng trinh bay d tren, gia sd ta ed eae gia tri xae djnh eua tdng bien sd nhu dien tich, rdng, be day tang ehda, v.v , tru lugng eiia md xem nhu da duge xac djnh Tuy nhien, rat it trugng hgp cd the tim duge mdt gia trj hang sd nhat dac trung eho tdng bie'n sd, ma thudng thi tdng thdng sd dugc cung cap dudi dang mdt phan bd vdi phuang sai va ky vgng rieng dac trung eho tdng khu vue khao sat Md hinh danh gia sd dung phuang phap md phdng Monte Carlo la phan md rdng ciia md hinh tieh djnh duge trinh bay d tren, sd dung mdt chuoi gia trj xac djnh cua eac thdng sd ehfnh rut td su phan bd cua tUng thdng sd Cd mdt gia trj rut tren eua tdng thdng sd, ta thay vao md hinh tien djnh se tim dugc mdt ke't qua cu the Nhu vay, nguyen ly ca ban ciia phuang phap md phdng se la xay dung tap hgp ciia tat ca ke't qua ma moi ke't qua cd duge ehfnh la td md hinh tien dinh Oae diem ehfnh ciia phudng phap la se tao mdt phan bd dac trung eua ket qua (trd lugng) dua vao cac phan bd eiia cac thdng sd chfnh (Hinh 1) Va ke't qua eua su phan bd tru lugng se dae trung eho mdc khdng ehac chan (do sai sd tiem an nao dd hay tin cay) viec danh gia tru lugng Chinh vi uu diem ma phuang phap danh gia md phdng duge sd dung het sde rdng rai edng nghiep, cu the la danh gia trd lugng eiia cdng nghiep dau khf , , , Cd the ndi ed rat nhieu phan mem ehuyen dung dan gian hda viec sd dung phuang phap nhu la @R1SK™, CRYSTAL BALL™; hay cung ed the sd dung eac ham Macro cd sin Excel, Mathead, Visual 113 Hoi nghj KHCN 2000 "Nganh Dau Viet Nam trffdc them theky 21' Basic, v.v de xay dung chuang trinh tfnh toan cu the Chi can xac djnh dugc bieu dd phan bd cua cae thdng sd chinh la ke't qua se dugc eung cap sau mdt thdi gian ngan Tuy nhien, khdng phai la da dugc thudng mai hda thi phuang phap md phdng dugc sd dung se khdng ed khuyet diem va sai sd Ve ban chat, cae van de gap phai ed the din de'n cae sai sd phat sinh sd dung khdng hieu qua phuang phap md phdng Monte Cario cd the liet ke nhu sau (i) tin cay "can thie't" cua ke't qua; (ii) lua ehgn phan bd cua cac thdng sd ehfnh; va (iii) mdc rang budc giua eae thdng sd nrio'inn p^ TriirlUtfngRs dUdc tinh bang tich so cQa thdng sd dudi day Bfirflngy Hes; 30% Do bao hoa nude tdi da 70% Vdi tieu ehuan da duge lap nhu tren, cd sd du lieu ban dau duge sang Igc va sau dd duge phan tfeh de' tim eae hinh anh ciia cac thdng sd dae trung chfnh thdng qua cac md'i quan he xae djnh td thuc nghiem Bdi vi chiing ta can tim thdng sd trung binh dac trung cho khu vue, nen nguyen ly ehfnh ciia qua trinh phan tich danh gia la dua vao su phan bd eiia eae gia trj trung binh cua cac thdng sd theo dien / khu vue chd khdng theo diem hay tdng gieng khoan Va ke't qua da eho nhieu phat hien rat bd fch se duge trinh bay ehi tiet sau Hdn nda, de' gia tang mdc dng dung eua ke't qua phan tfeh eua de tai nay, tac gia sd dung mdt vai thdng tin thuc te cua mdt md khf tieu bieu thude viing vjnh Thai Lan va sd dung cae gia thie't nhu sau: • Thanh phan khf khai thae duge d khu vue tuang tu nhu mau khf lay duge td mdt gie'ng khai thae tieu bieu khu vue; • Ap suat va nhiet eiia mdi trudng via dugc danh gia tuang tu nhu tai mdt gie'ng khai thae tieu bleu duge chgn - nghTa la cd quan he tang dan tuyen tfnh theo sau; • Md duge khai thae theo ehe khai thae can kiet theo kinh nghiem cac md khf da va dang khai thae d vung vjnh Thai Lan; Vdi sd lieu ed sin, ke't hgp vdi cae gia thie't neu tren, ea sd du lieu dugc phan tieh sd dung phuang phap hdi qui va md hinh ham phan bd dae trung eho tdng thdng sd Va ket qua la cac phan bd thu duge dac trung thfch hgp nha't eua eac thdng sd ehfnh cd the dugc tdm tat nhu Hinh 2, dd su phan bd cua cac thdng sd dae trung ehii yeu duge bie'u dien theo sau eua cae via dau khf tiem nang 3050 ^ F • — ' 2750 245C 2150 eu ZJ •ro 1850 sz O 1550 CO 0.30 11-13 14-16 17-19 20-22 23-25 26-28 29-31 32-34 D6 rSng trung binh (%) 06 r6ng 2900 2600 13 ID •CD ;5£ sz O 1700 1850 1400 120 140 160 H§ s6 gian ncr 116 2000 180 0.2 0.34 0.48 0.62 H§ sdthu hdi 0.76 0.9 Hoi nghj KHCN 2000 "Nganh Dau khf Viet Nam tnfdc them theky 21' Be day via (bo) 301-325 276- 300 251- 275 226- 250 201- 225 176- 200 151 175 126- 150 101- 125 in 76- 100 CO -75 -50 a-snn ^ , Hinh 2: Ket qua thu dirge td phan tfeh ca sd du lieu V; -: •:•;-;'' Nhu vay, dugc cung cap dien tfeh eua tdng tang ehda tai tdng sau xac djnh, ham phan b'd gia trj cua tdng thdng sd va md'i lien he giua eac thdng sd se duge xae djnh nhu hinh ve Vdi ke't qua tim dugc bien thien mdt pham vi rat hep nen so vdi viec sd dung toan bd sd lieu, tru lugng eac ham phan bd cac thdng sd cd the' dugc danh gia tin cay theo phuang phap md phdng Monte Cario KET QUA Ke't qua minh hga duge trinh bay, ed nhung diem chfnh nhu sau: :• Xac djnh cac phan bd xac suat thieh hgp nha't cho eae thdng sd chfnh dac trung eiia mdt md dau khf, gdp phan gia tang hieu qua va chfnh xac danh gia trd lugng; eu the la xay dung dugc dudng eong phan bd cua (i) rdng theo sau, (ii) bao hda dau khf theo rdng, (iii) be day tang ehda; (iv) he sd thu hdi khf, va (v) he sd gian nd khf theo chieu sau; • Xay dung md'i tuang quan giua eae thdng sd dae trung chfnh cd anh hudng ddng thdi fen qua trinh danh gia tru lugng Oieu se giam cac sai sd qua trinh sd dung phuang phap md phdng Monte Cario; cu the la da xay dung mdi lien he giua bao hda khf theo rdng cua tang ehda; • Tao dugc nhdng hinh anh cd kha nang trung thue eae thdng sd dae trung cho via dau khi, cho phep ket luan: khdng phai luc nao cung cd cae thdng sd via phan bd theo mdt dang ehuan nhu sach giao khoa (phan bd Idgarit eho cac thdng sd ciia via dau khf) Ndi each khac, khdng phai lue nao cac gia trj kinh nghiem dugc de cap tren sach gi&o khoa deu cd gia trj thuc tien ma mdi trudng dja chat nha't djnh, eac thdng sd se ed su phan bd rieng eiia ehfnh minh KET LUAN « Phudng phap md ohdng Monte Carlo cd the sd dung hieu qua viee danh gia trd lugng neu nhu van de chfnh cd the giai quye't thet de (1) tin cay "hieu qua" ciia ke't qua; (ii) lua chgn phan bd eiia cac thdng sd ehfnh; va (iii) mdc rang budc giua cae thdng sd • Mdi mdt khu vue dja chat rieng biet se ed mot hinh anh phan bd dae trung khae nhau, nen pham vi cua bai bao la ehi neu len phuang phap ly luan ehfnh lam ea sd vung chae trg giiip eho viec danh gia trd lugng cho mdt viing khai thae dau khL • Dd kien cd sin dugc cung cap la sd lieu rut td qua trinh minh giai dja vat ly gie'ng khoan eua eae md thude vLing hoat ddng eua edng ty Unocal Thai Lan tren 30 nam Do dd, ke't qua phan tfeh dd kien dd 117 Hoi nghj KHCN 2000 "Nganh Dau Viet Nam trffdc them theky 21' cd the sd dung hieu qua de danh gia trd lugng cho khu vue vung vjnh Thai Lan Ldi CAM ON Tac gia xin chan cam an cdng ty Unocal Viet Nam da tao dieu kien va cho phep cdng bd eac thdng tin dugc sd dung bai viet Hon nda, bai viet da khdng the hoan tat va den tay ban dgc neu nhu khdng ed su giup dd va ddng gdp y kien - kinh nghiem cua eac anh chj ddng nghiep, vi vay tac gia eung xin gdi Idi cam an sau sac den cac anh chj phdng tim kiem tham dd thude cdng ty Unocal Viet Nam va khoa Dja chat Dau trudng Dai hgc ky thuat Tp Hd Chf Minh TAI LifeU THAM KHAO Peterson S.K., Murtha J.A and Schneider F.F., Brief: Risk analysis and Monte Carlo simulation applied to the generation of drilling AFE estimates, JPT, June 1995, p 504 - 505.' Capen E.C., V\/hy lognormall, AAPG course notes of Rose P.R., 1999 Capen E.C., Dealing with exploration uncertainties, Chapter in "The Business of Petroleum Exploration", AAPG 1992 JhiC 118 Rose P.R, Chance of success and its use in petroleum exploration, Chapter in "The Business of Petroleum Exploration", AAPG 1992 f '; ': \i!' ... tfeh tu dau 15 Hoi nghj KHCN 2000 "Nganh Dau Viet Nam tnfdc them theky 21'' khf duge xem nhu la khdng tdn tai neu khdng cd kha nang khai thae hoac kinh te" Cac tieu chuan duge trinh bay Bang Bang... thude vLing hoat ddng eua edng ty Unocal Thai Lan tren 30 nam Do dd, ke''t qua phan tfeh dd kien dd 117 Hoi nghj KHCN 2000 "Nganh Dau Viet Nam trffdc them theky 21'' cd the sd dung hieu qua de danh... Viet Nam da tao dieu kien va cho phep cdng bd eac thdng tin dugc sd dung bai viet Hon nda, bai viet da khdng the hoan tat va den tay ban dgc neu nhu khdng ed su giup dd va ddng gdp y kien - kinh