Hoi nghj KHCN 2000 "Nganh Dau khi Viet Nam trifdc them theky 21'
M O T S O KET QUA NGHIEN COU TRONG VIEC H O A N THIEN, AP DUNG GIAI P H A P K H O A N GIENG CO THAN NGANG, A NGANG TAI XNLD VIETSOVPETRO
Nguyen Van Ut, Truang Cong Tai. Phung Hiru Thuac Vien NCKH&TK XNLD"Vietsovpetro"
TOM TAT
Mot trong nhdng giai phap tang cudng khai thac dugc ap dung rong rai trong cong nghiep khai thac dau khi la giai phap khoan gieng than ngang, a ngang.
Trong bai viet tnnh bay mot so ket qua ap dung cong nghe khoan nay tai XNLD Vietsovpetro va de xuat phuang phap tinh toan hugng khoan toi uu doi vOi da nui ne
M d O A U
Mpt trong nhtirng giai phap tang cudng khai thac dugc ap dung rdng rai trong cdng nghiep khai thac dau khi la giai phap khoan gieng than ngang, a ngang. Giai phap nay dac biet quan trpng eho cac md khai thac ngoai bien, cung nhu cae via dau khi ed chieu day chura dau khdng Idn va vdi mdt sd lugng cdng trinh bien han che.
Ngay nay, cdng nghe nay dang tren da phat trien va hoan thien, trd thanh mdt trong nhtrng giai phap quan trpng, giai quyet dugc nhu'ng van de trong chien luge phat trien md trong viec hinh thanh he thdng mang ludi gieng khoan khai thac va bam ep nude, dam bao mat dp bao trum ciia gieng va tan khai thac tai nguyen mdt each hgp ly.
Mot trong nhurng giai phap tang eudng khai thae quan trpng da va dang ap dung rdng rai d XNLD Vietsovpetro la cdng nghe khoan gieng than ngang va a ngang. Trong pham vi bai viet tac gia thdng tin ket qua thu dugc qua mdt vai nam ap dung edng nghe khoan gie'ng ngang, a ngang eho ddi tugng tang mdng md Bach Hd tai LDDK Vietsovpetro, ddng thdi trinh bay mdt sd ket qua nghien ciru trong viec hoan thien cdng nghe nay.
OAC OIEM Hin N^ CAC T H A N H T A O GRANITOID MONG M 6 BACH HO
Be mat mdng trudc Kainozoi ciia md Bach Ho theo cau true hinh thai dja mao dugc chia ra 3 vdm:
vdm Bae, vdm Trung tam va vdm Nam. Cac thanh tao mdng duge dac trung bdi dae diem thach hpc khdng ddng nhat bao gdm cac da xam nhap ed thanh phan tU diorit, granodiorit tdi granit, granit alaskit.
Tren ea sd ddi sanh vdi cac phirc he maema xam nhap phan luc dja mien Nam Viet Nam vdi cac da mdng md Bach Hd theo cac dae diem thach hpc, thach dja hda, nguyen td vet, tudi ddng vi phdng xa da cho thay:
Oa ed tudi trudc Kainozoi ciia md Bach Hd cd the chia thanh 3 phirc he maema xam nhap: phire he Hdn Khoai, phire he Ojnh Quan va phirc he Ca Na [1]. Theo cae tai lieu dia vat ly nghien ciru khe nirt trong cae Id khoan va cac md ta khe nirt trong cac mau khoan phire he Ojnh Quan bj nirt ne kha manh me. Mat dp khe nirt trung binh khoang 17-18 khe nirt /10m, eao nhat cd the dat den 60 khe nirt /10m (gie'ng 65). Trong cac mau khoan cd doan da bj ea nat rat manh me. Qua phan tich cac bieu dd khe nirt trong Id khoan da ghi nhan trong thanh tao nay phat trien manh nhat la nhdm khe nirt phuang Tay Bae - Odng Nam dac biet la theo phuang 145°. Thir den la nhdm khe nirt phuang a kinh tuyen va phuang Odng Bae - Tay Nam. Nhdm
khe nirt phuang a vl tuyen phat trien yeu nhat. Nhin chung cae khe nirt thuang ed gdc cam kha thoai va dao dpng trong khoang kha Idn 10-70° it thay cae khe nirt thang dirng. Tuy nhien, trong cac m i u khoan thi cae khe nirt ed gdc cam tU 70-90° lai chiem ty trpng kha Idn. Phan Idn (85%) cac khe nut d day thudc loai khe nirt md ttrng phan hoae khe nirt ddng kin. Vi khe nirt md chiem ty trpng it han 10-15%.
Theo cac tai lieu dia vat ly nghien ciru khe nirt trong cac Id khoan va cac md ta khe nirt trong cac mau khoan thi cac thanh tao eiia phirc he Ca Na bj nirt ne kha manh me. Mat dp khe nut trong cac Id khoan khoang 15 khe ntrt /10m, eao nhat d nhung doan bj ca nat mat dp cd the dat 45 khe nirt /10m. Qua thdng ke va phan tich eae bieu dd khe nirt do trong Id khoan da ghi nhan dugc 7 he thdng khe nirt nhu sau:
-He khe nirt phuang 150° cam 60-70° ve phia Odng Bae,
-He khe nirt phuang a vT tuyen cam 60° ve phia Nam.
-He khe nirt phuang a kinh tuyen cam 65-70° ve
\ phia Odng.
90 -He khe nirt phuang 45° cam 50-60° ve phia I Odng Nam.
/ -He khe nirt phugng 60° cam 60° ve phia Odng ,/ Nam.
-He khe nut phuang 25° cam 70-80° ve phia Odng Nam
-He khe nirt phuang 130° cam 50-60° ve phia Odng Bae
1270
Hinh 1. Oae trung khe nirt trong thanh tao Ca Na
mdng md Bach Hd Cac tai lieu tren cho thay phat trien manh nhat la nhdm khe nirt phuang Odng Bae - Tay Nam ma chii yeu la phuang 45° thir den la he TB-ON (phuang 150°) va phuang a kinh tuyen (28%). He khe nirt phuang a kinh tuyen phat trien yeu han ca. Phan Idn khe nirt deu ed gdc cam trung binh 60-70°, thudc loai ddng kin hoae md mdt phan (42%) va vi khe nirt md (38%). Cac vat chat lap day trong cac khe nirt phan Idn la cac mach zeolit va calcit mau trang, trang phdt xanh vdi kich thudc mach <1mm. (Hinh 1)
Mat khae, cae dac trung nirt ne xac djnh theo dia vat ly gieng khoan cd nhugc diem quan trpng la khdng phan anh dugc gia trj cho ca mien xa gieng khoan ma chi phan anh gia trj do d vung can thanh gieng khoan. Trong dieu kien ed su bat ddng nhat cao ve dp tha'm ciia tang mdng md Bach Hd, eae gia trj dp tha'm xac dinh theo dia vat ly gieng khoan cd y nghla so sanh vdi phuang phap nghien ciru thiiy ddng luc hpc chi trong mdt gidi han nao dd.
Op tham xac djnh theo mau Idi, theo dia vat ly gieng khoan va theo nghien eiru thiiy ddng luc hpc deu phan anh dac tinh bat ddng nhat cao va bien ddi kha phirc tap ciia mo, ca theo chieu sau than dau va theo tung Idp nam ngang.
Tren ea sd minh giai ket qua xir ly tai lieu dja chan 3D, ddi sanh vdi cac tai lieu dia vat ly gie'ng khoan (FMI) cung nhu cae sd lieu kiem tra khai thac tang mdng md Bach Hd, ddi sanh vdi cac ket qua nghien ciru dirt gay d luc dja trong bao cao [1] cho phep nhan biet dugc 3 nhdm dirt gay ehinh trong mdng granitoit md Baeh Ho vdi kha nang bien ddi tinh chat tha'm chira khae nhau [5]:
- Cae dirt gay cd phuang keo dai Odng Bae - Tay Nam (30°-210°). Cdc dirt gay nay cd gdc ddc kha
Hoi nghj KHCN 2000 "Nganh Dau khi Viet Nam trifdc them theky 21'
Idn (55°-65°) hoae dd ve phia Odng Nam (120°) hoae dd ve Tay Bae (300°)
- Cac dirt gay cd phudng keo dai phUdng kinh tuyen (0°-180°), a kinh tuyen (0°± 10°). Cac dirt gay nay phan Idn la dirt gay nghjeh cd gdc dd chii yeu 60°-70° ddi nai ed gdc dd gan thang dirng.
- Cac dirt gay nghjeh cd hudng dd Odng Nam vdi gdc dd 55°-60°, he dirt gay ngang phai thuan vdi phuang keo dai 55°-60°. Cae dirt gay nay dd ve hudng Odng Nam (145°-150°) hoae Tay Bae (325°-330°).
Nhu vay, hien nay ddi vdi tang mdng md Bach Hd [5] giti^a dae trung nirt ne eiia da mdng va su tdn tai cac mien dat da maema khae nhau cd md'i quan he mat thiet va eae dirt gay kien tao ed vai trd chu dao trong viec thanh tao nhung viing dap nat, nirt ne da chira tang mdng.
M O T S O K E T Q U A BLTdC OAU TRONG VIEC AP DUNG CONG NGHE KHOAN GIENG T H A N
NGANG, A NGANG
Tir nam 1995, d Vietsovpetro da tien hanh khoan gie'ng than ngang, a ngang, den nay taj md cd gan 30 gie'ng khoan cd than ngang hoae a ngang. Mdt trong nhtrng ddi tugng khai thae ap dung rdng rai cdng nghe nay la ddi tugng khai thae trong tang mdng via dau da ehira nirt ne cd tinh chat tha'm ehira rat dac thii.
Mat khae, ap dung cdng nghe khoan ngang cho ddi tugng mdng da chira nirt ne ngoai viec tang cudng san lugng khai thae cdn cd mdt vai trd quan trpng trong viec hoan thien he thdng gie'ng khai thac va bam ep eho ddi tugng nay.
Trong chien luge phat trien md dau trong mdng da chira nirt ne, mdt trong nhQng giai phap quan trpng la bam ep nude vao via, giir ap suat via khdng ddi vdi ty le giu'a gieng khai thae va bam ep la 2/1. Cd nghla la gie'ng bdm ep phai cd dp tiep nhan Idn han 3 lan luu lugng gie'ng khai thac dau. Theo [2], qua trinh khai thac via dau trong tang mdng md Bach Hd dugc thuc hien bang viec chia qui udc than dau trong tang mdng thanh 3 viing: viing I viing tiem an qua trinh tach khi, vting II viing khai thac chinh va viing III vting bgm ep nude. Trong cac giai doan khai thae tiep theo, trong [3] qua trinh khai thae dau duge thuc hien bang he thdng phan bd gie'ng khai thac bam ep trong hai vting ca ban: gieng khai thac md va khai thac d vting I cd chieu sau tuyet ddi den 3700m, gie'ng bam ep md va bam ep nude vao via vao viing II cd chieu sau tuyet ddi dudi 4000m.
Mat khae, tinh chat tha'm chira cua da chira giam manh theo chieu sau than dau, vi vay, thuc hien chu truong tren vdi mpt sd lugng gie'ng bgm ep han che dam bao bti khai thac bang bam ep nude tan dung khai thae tai nguyen mot each hgp ly va dap irng nhu cau qudc gia ve dau khi la mdt nhiem vu khd khan dat ra trudc cae nha thie't ke gieng tai XNLD Vietsovpetro. Ap dung cdng nghe khoan gie'ng cd than gie'ng ngang, a ngang da phan nao hd trg giai quyet van de tren mdt each ca ban.
Trong giai doan dau thuc hien sa dd edng nghe nam 1995, tai XNLD Vietsovpetro da tien hanh khoan cac gieng bam ep thing dirng: 65,809, 407, 415, 431, 905, 813, 442, 903, 445, 412, 426. Ket qua khoan gie'ng cho thay dp tiep nhan eiia cac gieng nay khdng dam bao, ty le thanh cdng khdng cao hoae phai bam vao viing cao ciia md (gie'ng 905, 8, 421, 433, 424, 425, 911, 914), hoae bam vdi luu lUdng nhd (gie'ng 88, 425,911,100,405).
Nang suat gieng khoan vao via da ehira nirt ne phu thudc rat nhieu vao mat dd, dp md cua nirt ne ma gieng md via. Vdi muc dich nang cao hieu suat ciia gieng bam ep, cung nhu khae phuc nht/ng yeu kem ciia he thdng gieng khoan thing dirng, trong qua trinh thie't ke gie'ng khoan cac nha thiet ke da manh dan de xuat giai phap khoan gie'ng cd than ngang, a ngang cd tinh toan kha nang khoan djnh hudng vao viing dap nat, dirt gay.
Phan tich ket qua khoan gieng than ngang, a ngang eho thay:
• Cae gieng khai thac (gieng 457, 428, 440, 438, 439, 479, 467, 456) cd ty le thanh cdng rat cao 6/8, gie'ng cho luu lugng dau Idn tU 800 den 1300 tan/ngay. Cac gie'ng 467, 456 khdng thanh cdng.
• Trong 11 gie'ng bam ep cd than a ngang (gie'ng 455, 435, 464, 427, 452, 921, 465, 443, 447 ,458, 449) nhan thay 2 gieng 458, 449 cd nang suat khdng dat yeu cau. Cac gie'ng bam ep nay cd dp tiep nhan trung binh kha cao (>3300 m^/ngay).
• Theo ket qua minh giai, phan tich tai lieu dja chan 3D mdi nhat d XNLD Vietsovpetro thi cac gieng 467, 456,458,449 dugc khoan vao viing xa cac dirt gay kien tao.
Tai diem 01.01.1999, san lugng dau tU cac gie'ng than ngang, a ngang chie'm 25,42% tren tdng sd lugng dau khai thac ttr md Bach Hd, trong khi dd ty trpng quy gie'ng chi chie'm 13,67%.
TINH TOAN Ht/ONG KHOAN GIENG TOI lAJ CHO LlAJ Lt/ONG LON.
Kha nang khai thac dau tU cac via nirt ne tu nhien bang mdt he thdng gieng khoan la gidi han. Vi vay, viec xac djnh hudng khoan de thu hdi dugc nhieu dau la- rat quan trpng. Tac gia [4] diing phuang phap phan tich tuyen tren mat phang de tim kha nang khoan qua mdt each Idn nhat cac nirt ne, suy rdng de xac djnh ty le ddng chay trong nurt ne Idn nhat cua gie'ng. Sau dd phan tich nay dugc tdng quat hon cho trudng hgp ba chieu trong thuc te.
Cac nirt ne dugc khao sat nhu mpt tap hgp nirt ne - mdt he thdng nirt ne, co ciing hudng phat trien, cd khoang each deu nhau (S*) va mdt dp md dac trung (e). Hudng khoan tdi uu ciia gieng phu thudc vao nhieu yeu td nhu dp md, khoang each, su djnh hudng ciia mdi he thdng nirt ne.
Trong trudng hgp chi cd mpt he thdng nirt ne dan vudng gdc vdi the nam via (Hinh 2), cd khoang each bieu kien ciia nirt ne (S) trong mat phang phan Idp. Theo djnh ly Pytago:
S = S* l + t a n g ' p ] " ' = S * [ l + t a n g ' ( e - k ) ] "
(1)
Trong dd:
S*: khoang each gitta cac nurt ne (the closest fracture spacing) 9: gdc phuong vj CLia S*
k: gdc phuang vj ciia S
Tap nirt ne
Bae Gocphirang vi o S^S^'^ va P
Tap nut ne 1
Tap nut ne 2
Hinh 2
Hoi nghj KHCN 2000 "Nganh Dau khi Viet Nam trifdc them theky 21'
Khi dd, k ed the duac xem nhu la gdc phuang vi diing trong khoan dinh hudng. Tan suat ma than gieng khoan chan qua cac nirt ne dugc gpi la "ty le chan nirt ne " (P) va chinh la sd cac nirt ne (n) bi chan tren mpt dan vj chieu dai eiia gieng (L). Ty le chan nirt ne chinh la sd nghich dao cua chieu day bieu kien ciia nirt ne vdi hudng k. Ty le chan nirt ne (P) duge xac djnh:
L S S*[l + tang'(e-k)
,1''2 (2)Vdi muc dich tim ra hudng k de cd the chan dugc hau het cae nirt ne trong sudt chieu dai gieng va tim ra hudng de ty le chan cac nirt ne la cao nhat. Oe dat dugc muc dich nay, P dugc hieu nhu la mdt ham theo k.
Lay vi phan phuang trinh tren theo k va cho bang 0 ed:
dP 1
= 0 = -^smie-k)
dk S*
(3)Phuang trinh (2), (P), dat gia tri Idn nhat hay nhd nhat khi k = 0, k = 6. Phuang trinh (3) bang 0 khi khdng cd nirt ne trong via, tire la S* = co, hoae khi sin(6 - k) = 0, (9 - k) = 0, ±7t, ±2:1 , t m n , tat ca cac gia trj nay deu tdn tai cung phan tich nay.
Oao ham bae hai ciia P theo k la:
d-p
s-
COS'
(e-k)
(4)9P/3k = 0 irng vdi gia tri Idn nhat ciia P (phuang trinh 2) khi 0 = k, dao ham bae hai cua P < 0. Nhu vay, ddi vdi mpt tap nirt ne dan, hudng k, ty le chan nut ne P dat gia trj Idn nhat khi dat song song vdi hudng (9) cua cac nirt ne. Hudng khoan tdi uu la hudng vudng gde vdi mat phang ciia eae mat nirt ne.
Md rdng tinh toan xem xet den dd md ciia nirt ne dugc cho:
FN- +-
1/2 (5)S;[l + tang-(e,-k,.)J - S;[l = tang'(e2-k,.)
Tri/dng hdp tong quat:
Viec tinh toan tren hinh hpc phang ed the dugc md rpng cho nhieu tap nirt ne thang durng
^I r s:[l+tanr(e,-k,.)]" (6)
k, =arctang
^ e ?
sinG;
N p^
z
eosB, (7)Trudng hgp tdng quat, cac tap nirt ne va than gieng cd the ed su djnh hudng trong khdng gian 3 chieu:
He thdng nirt ne dugc xac djnh bang gdc phuang vj (9,) va gdc cam (a^). Than gie'ng khoan cung duge xac djnh bdi gdc phuang vj (k) va gde khoan so vdi mat phang ngang (8). Khoang each giua cac nirt
ne theo hudng eua than gieng, khoang each bieu kien cua nirt ne (S,) theo hudng than gieng, dugc xac dinh bdi:
S,=S,
l+tang^(e, -k)+tang'(a, -6)]"^ (8)Ty le chan nirt ne theo hudng cua than gieng P''" la ham nghjeh dao ciia chieu day nirt ne bieu kien theo hudng than gie'ng:
\_ 1 S,
pk.S _
l+tang^(0, -k) + tang'(a, -5)
1/2 (9)Vdi 1 tap nirt ne, P^'* dat gia tri Idn nhat khi hudng than gieng vudng gde vdi nhung mat phang tuang duang tap nirt ne dd hoae khi hudng than gie'ng trung vdi hudng S" eiia tap nirt ne. Oieu kien xay ra khi k =
0iVakhi5 = a , .
Viec md rdng cung tudng tu nhu bai toan phang cho hai hay nhieu tap nurt ne. Dang tdng quat, ty le chan ddng chay trong nirt ne dugc tinh bang:
p , ' " = z - T ^ — - — ! — . . . _ .11/2 (10)'
i=i
l + tang^(e,-kf) + tang^
' ( 9 , - 5 , ) ] ' "Ttr phugng trinh 10, hudng khoan (k„ 5,) cho ty le chan nirt ne Idn nhat Pj' cd the dugc xac djnh nhd may tinh. Mdt each dgn gian, Idi giai eua bai toan nay ed the duge tien hanh nhu sau: vi gde phuong vj 9; va k, thay ddi ttr 0 den 360° va dp ddc a, va §, bj gidi han trong khoang ttr 0 den 90° nen Pj'' la mdt ham theo k( va 6, va gia trj ciia nd cd the dugc xac djnh tren may tinh.
KET LUAN VA M O T SO VAN 0£ TON TAI TRONG VIEC NGHIEN CtX) AP DUNG CONG NGHE KHOAN GIENG CO THAN NGANG, A NGANG TRONG KHAI
T H A CDAU.
1. Cdng nghe khoan gie'ng cd than ngang, a ngang da va dang ap dung rdng rai d XNLD Vietsovpetro.
2. Cdng nghe nay da khang djnh vai trd cua chiing trong viec tang cudng khai thac cac via dau ma dac
• biet la via dau trong da mdng nirt ne md Bach Hd. Hieu qua eiia giai phap khdng dirng d viec tang cudng khai thac ma cdn gdp phan hoan thien he thdng gieng khai thac va bdm ep. Tao dieu kien tan dung khai thac tai nguyen Idng dat mdt each hgp ly.
3. Hien nay, ddi vdi tang mdng md Bach Hd nghien ciru cac dae trung nirt ne ciia da mdng gan lien vdi su nghien ciru sutdn tai cae mien dat da maema khae nhau, su nghien ciru cac dac trung ciia dirt gay kien tao cung nhu viec thanh tao nhtrng vting dap nat, nirt ne da ehira tang mdng.
4. Cae tinh toan hudng khoan trong nhieu trudng hgp mang tinh udc lugng, thuc te cae sd lieu nghien ciru cac dac trung nirt ne trong da ehira tang mdng md Bach Hd rat han che. Trong tuong lai can thie't tang cudng nghien ciru theo hudng nay.
TAI LIEU THAM KHAO
1. PTS Pham Huy Long, PTS Trinh Long. "Nguon goc thanh tao, dac diem nirt ne, dirt gay da mong granitoid viing mo Bach Ho, Rong va viing kecan". Bao cao de tai NCKH , tp Ho Chi Minh 1996.
2. Vien NC&TK Dau khi bien, XNLD Vietsovpetro. "Sa do cong nghe khai thac va xay dung mo Bach Ho",
Hoi nghj KHCN 2000 "Nganh Dad khi Viet Nam tri/dc them theky 21'
Vung Tau 1995.
3. Vien NC&TK Dau khi bien. "Hoan thien chinh xac hoa sa 66 cong nghe khai thac va xay dung mo Bach Hd", Vung Tau 1998.
4. Richard C. Nolen-Hoeksema and J. H. How/ard. Estimating Drilling Direction for Optimum Production in a Fractured Resen/oir, The American Association of Petroleum Geologists Bulletin V. 71 No 8 (August 1987), P 958-966.
5. Nguyen Van Gia. XCr ly va phat then thong tin ve do tham phuc vu thet lap mo hinh khai thac dau trong da mong mo Bach Ho. Bao cao de tai NCKH, tp Hd Chi Minh 1997