Tuygn tap bao cao HQi nghj KHCN "30 nam Phu khi Viet Nam Co" hoi mdi, thach thiic mdi'''''''' 591 PHirONG PHAP PHAT HIEN, XAC DINH VA DU^ BAO DI THlTCJNG AP S U A T d BE NAM CON SON Nguyen Dinh Ha Schlumber[.]
Trang 1Tuygn tap bao cao HQi nghj KHCN "30 nam Phu khi Viet Nam: Co" hoi mdi, thach thiic mdi'' 591
PHirONG PHAP PHAT HIEN, XAC DINH VA DU^ BAO DI THlTCJNG AP
S U A T d BE NAM CON SON
Nguyen Dinh Ha
Schlumberger
TOM TAT
Anh hu&ng cua di thu&ng dp sudt ddi v&i bdt cir hi thdng ddu khi ndo cung rdt phirc
tgp, ddc bid ddi vdi be Nam Cdn Son, noi cdc hiiu biit vi cdc ddc diim cua hien tugng ndy
ddng vai trd rdt quan trong, dam bdo tinh hiiu qud cua cdng tdc tim kiem thdm dd ddu khi
Bdi bdo trinh bdy kit qud nghien ciru cdc phucmg phdp ky thudt nhdm phdt hiin, xdc
dinh vd du bdo di thucmg dp sudt xdy dung cho bi Nam Cdn Son nhdm gidm thieu muc do
dnh hu&ng cua cdc tdng di thuong dp sudt len cdng tdc khoan thdm dd Trong dd, rdt
nhiiu su cd, rui ro nghiim trong gdy b&i di thu&ng dp sudt da gap phdi trong cdc giai
dogn tim kiim thdm dd ddu khi & be Nam Cdn Son
Tdc gid da thuc hiin phdn l&n cdc thuc nghiem cua nghien ciru ndy trong th&i gian
cdng tdc ciia minh & Viin Ddu Khi, Tdng cdng ty Ddu khi Viet Nam Cdc cdng viec ndy
dugc thuc hiin trong cdc ndm tir 1990 din 1996, khi cdng tdc tim kiem thdm dd gap khd
khdn vd phi tdn do hiin tugng ndy gdy ra tgi mdt logt cdc giing khoan (Lan Tdy, Mdc
Tinh, Thd Tinh, Thanh Long, Bd Cdu, Sdng Tiin, Hdi Thgch, v.v.)
Su xudt hiin cua di thucmg dp sudt dugc ghi nhdn trong rdt nhiiu giing khoan tren
phgm vi rdng l&n bao gdm cdc Id: 4, 5, 6 vd Id 12 Ap sudt via xdc dinh dugc tgi cdc giing khoan ndy dgt cdc gid tri tir 1,65SG (13,75PPG) din 2,1SG (173PPG) Do sdu cdc tdng
dp sudt cao thay ddi tu 1200m din 3800m
Nghien cun ndy tru&c hit tdng hgp cdc phuang phdp khdc nhau nhdm phdt hien vd xdc
dinh di thu&ng dp sudt mgt each dinh lugng tir ede tdi lieu thu duge sau khi khoan Cdc kit
qud ndy sau do dugc kit hgp phdn tich v&i tdi lieu dia chdn de tinh dp sudt via tir gid tri van
tdc dia chdn Cae kit qud tinh todn dugc hiiu ehinh chudn hod vtdi tdi lieu khoan nhu cdc
thdng sd khoan, sd lieu do dia vgt ly giing khoan (DVLGK) tru&c khi dugc sir diing nhdm du
bdo dp sudt via eho cdc giing khoan m&i ndm trin ciing mdt lu&i tuyen dia chdn
PHAT HIEN, XAC DEVH VA Dif BAO DI THUTOfNG AP S U A T 6 BE NAM CON SON
2 Cac phuong phap phat hien di thirdng ap suat
O be Nam Con Son, sir dung nhom phuong phap nay, chii yeu dua vao viec nhan dang
sir bien d6i cac th6ng s6 hoae 16 hgp cac th6ng s6 dia vat ly do dugc trong va sau khi khoan
Viec phat hien di thudng ap suat trong khi khoan bao g6m viec xac dinh cac th6ng s6 khoan,
th6ng s6 dung dich khoan, dudng cong khf, miu Slam va cac dudng cong do dia vat ly trong
khi khoan Sau khi khoan sir dung cac dudng cong DVLGK nhu: dien trd, sieu am, mat do,
phong xa Gamma, v.v va cac tai lieu thir via Hinh 1 va 2 trinh bay sir biin dii ciia cac dang dudng cong ph6 bien d be Nam C6n Son khi di qua vimg di thudng ap suit
Trang 2592 Phuong phap phat hien, xac djnh va du- bao dj thudng ap suht d bg Nam^^dnjgjl
50O
lOOO
O
1
J 500
20QO
250O
1-1
Hinh 1: Cac duong cong mat do dung dich, he so mu "d", % khi va gradient nhiet do
tinh tir tai lieu khoan, 16 04, be Nam Con Sffn
a Su" dung tdc dp khoan
Sir thay d6i t6c do khoan lien quan den sir thay d6i ciia do r6ng, do vay, day la mot each nhan biet tang "thieu nen ep" co di thudng ap suit Do cd rit nhilu ylu t6 anh hudng den t6c do khoan nhu thach hgc, do nen cua dat da, chenh ap, sire nang dat len miii khoan, toe do vong quay, m6men quay, thuy dgng lire, loai miii khoan va mirc do mon, v.v dl tang do chinh xac cua phuang phap nay cin sir dung cac thong s6 khoan t6ng hgp ggi la
he s6 mii "d" Theo Bingham ta co mli quan he:
R/N = a (W/D)'' Trong do: R la t6c do khoan, N la t6c do vong quay, W la tai trgng tren mui khoan,
D la dudng kinh miii khoan, a la he s6 thach hoc, d la he s6 dac trung cho mirc do nen ep (di thudng ap suat)
b Su- dung tdi lieu dia vgt ly trong khi khoan
Tai lieu do dia vat ly trong khi khoan cho biet mgt loat cac th6ng s6 via nhu dien trd, cudng do phong xa, v.v Do vay, cac th6ng s6 nay c6 the dugc sir dung de phat hien va hieu chinh do sau ciia tang ap suat cao
Trang 3Tuygn tap bao cao Hdi nghj KHCN "30 nam Dau khi Viet Nam: Co' hdi mdi, thach thuc mdi' 593
c Sw dung du&ng cong diin tr&
Phuang phap dien trd la mgt trong nhtrng phuong phap dugc dimg sdm nhal de nhan bilt va xac dinh di thudng ap suit Khi ning do khoang hoa thay d6i kh6ng dang ke thi dien trd ciia set (R^) lien quan true tilp din do rong Theo do sau, do nen ep tang lam giam do r6ng din din R; tang len mgt each tir tir Tai khu vuc di thudng ap suat, gia tri R^ giam dang ke so vdi gia tri binh thudng Dudng bieu thi m6i quan he giOa Rj va do sau co dang nhay bae
d Sir dung dw&ng cong siiu dm
Dudng sieu am (AT) la mgt trong cac dudng cong dia vat ly gieng khoan cho do tin cay cao nhat trong viec xac dinh ddi thieu nen ep th6ng qua viec xac dinh do r6ng ciia set Neu thanh phan thach hgc va sir phan b6 do r6ng la tuong d6i d6ng nhat, m6i quan he giQa
do r6ng va t6c do truyen s6ng trong via dugc xac dinh theo c6ng thirc: AT = O.ATf +
(1-0)ATm d day: AT la khoang thdi gian truyen song (~1/V), ATf va AT^ la thdi gian truyen
song trong chat luru bao hoa va trong khung da, O la do r6ng
e Sw dung du&ng cong mat dp
Dudng cong mat do dugc sir dung de phat hien cac tang thieu nen ep Gia tri mat do kh6i dugc tinh theo c6ng thirc: Pb= (l-0)pm+ O.pf Trong do: Pb la mat do kh6i do dugc, Pm la mat
do khung da, p,- la mat do chat luu Dac biet cac gia tri mat do do dugc con dugc sir dung de tinh
ap suat dia tTnh, mgt th6ng s6 quan trong trong viec xac dinh dinh lugng ap suat via
/ Sw dung dw&ng cong Gamma tw nhiin vd pho Gamma
Cac dudng Gamma (GR) va ph6 Gamma cho th6ng tin ve cac tang set cung nhu do sach cua chiing Su xuat hien ciia cac tang set tai cac do sau nhat dinh d be Nam C6n Son
la mot trong cac yeu t6 quan trgng lien quan den hien tugng di thudng ap suat
JSOOU-Dien i m
0 AMP NORM 2
Sieu iim |
150 u sec too;
z z j i
Viing iip sual f~
binh Ihirong ^,r^
, ,"! _J3L Viing iip sual cao
Mat do
2 gm/cc 2.5
>
R»h = 0.4 n 1 4 0 ,«J5 s«c
xL
.t
3.11 g m / t c
Hinh 2: Sy bien doi ciia cac ducmg cong DVLGK khi qua vung ap suat cao
2 Cac phuong phap xac dinh ap suit via
Phan ldn cac phuang phap xac dinh ap suit via co ban dua vao sir so sanh tuong doi giua che do nen binh thudng va thieu nen ep dugc phan anh len cac tham s6 DVL do dugc khae nhau Phuong phap xac dinh ap suit via dugc img dung tit trong m6i trudng trim
Trang 4594 Phuong phap phat hien, xac djnh va du bao dj thudng ap suat d bg Nam^^£_Son^
lich luc ngu}'en va co the ap dung cho hau het cac dudng cong DVLGK Mot irong cac th6ng s6 quan trong nhat trong viec xac dinh ap suat via la ap suit dja tTnh (S) Day la thong s l cho chiing ta biet mirc do nen ep trung binh theo chieu sau cua khung da
a Xdc dinh dp sudt dia tinh theo tdi lieu DVLGK
Viec xac dinh ap suat dia tTnh theo tai lieu DVLGK la bude di co ban da dugc lien hanh cho be Nam C6n Son Ap suat dia tTnh dugc tfnh tir cac s6 lieu ciia duo^ng cong mat do d6i vdi cac via set Cac gia tri mat do nay thu dugc tir cac phep do DVLGK va co d6i sanh vdi tai lieu phan tich miu dugc lay tir cac gieng khoan khae nhau tren toan be Ap suat dia iTnh dugc tinh theo c6ng thirc sau: S = Pb.Z/10 Trong do S la ap suat dia tTnh co don vi la (kg.cm'~), Pb la mat
do trung binh ciia da co don vi la (g.cm'^), Z la do day thang dung ciia cot dat da tram tich co don vi la (m) Do cac gia tri mat do do dugc kh6ng lien tuc trong su6t chieu day cua via nen cong thirc tren c6 thi dugc viit thanh: S = EL|.p/10 (i = 1, n) Trong do: S la ap suat dia tTnh (kg/cm^), L, la khoang do sau trung binh (m), p, la mat do trung binh
b Diim siiu twang duang trong tinh dp sudt
Nguyen ly "diem sau tuong duong" trong tinh ap suat dugc ap dung cho hau het cac phep
do true tiep hoae gian tiep do r6ng M6i mgt diem A nam trong viing thieu nen ep cua da set tuong U'ng vdi mot diem B nam trong viing nen ep binh thudng Mirc do nen ep tai hai diem nay
la luong duong hay (aA= CTB) DO sau tai diem B (ZB) dugc goi la do sau tuong duong
\ ^ fi -a —
.r -PB = 2250.1,06/10 = 239 (Kg/cm^)
SB = 2250.2,11/10 = 475 (Kg/cm^)
;A = 2950.2,18/10 = 646 (Kg/cm")
B + ( S A - S B ) = 410 (Kg/cm')
A T l u S e c / n
Hinh 3: Tinh ap suat via tii' duong cong sieu am d be Nam Con Son
Trang 5Tuygn tap bao cao Hdi nghj KHCN "30 nam Dau khi Viet Nam: C o hdi mdi, thach thiic mdi" 5 9 ^
Ta co: SA = PA + <^A; SB = PB + '^B, irong ^o S la ap suit dia tTnh, P la ap suit thanh
he, a la img suat hieu dung
Vi: G^= OQ, do vay ta co: P A = PB + (SA-
SB)-Hinh 3 m6 ta kit qua tinh ap suit via tir dudng sieu am theo nguyen ly nay trong do
gia tri ap suat dia tTnh dugc tinh theo c6ng thirc da neu
c Phwang phdp lay ty sd vd phwang phdp Eaton
Cac gia tn quan sat dugc ciia xu the nen ep ty le thuan vdi viec tang ciia ap suat tai
ciing mgt do sau Phuang trinh tinh mat do can bang nhu sau:
deql= dgqin-dCn/dCo
Trong do: dgqi va deqin la gia tri mat do can bang d diem quan sat va d che do ap
suat binh thudng, dCp va dco la gia tri d d che do ap suat binh thudng va d diem quan
sat
Tir c6ng thuc tren ta cd:
dCo= dCn dgqin/ dgq]
Phuong trinh ty le nay co the dugc don gian boa bang cac dudng d6ng mirc
(deqin/dcqi) soug soug vdi uhau CO gia tri cho trudc
Eaton da dua ra c6ng thiic thuc nghiem dugc hieu chinh tir cac tai lieu thuc dja
nhu sau:
P = GG - 0,535 X [(Rshquan sat)/(Rshbinh thudng)]'-^
Trong do: P: la gradient ap suat via, GG: la gradient ap suat dia tTnh, R^^: la dien trd
ciia set Phuang phap ty le noi chung va phuong phap Eaton ndi rieng kha don gian nen
dugc ung dung rgng rai
3 Cac phirong phap dy bao dj thu'ong ap suat
a Phwang phdp dw bdo dp sudt via trong khi khoan (dw bdo gdn)
Ung dung cac c6ng nghe hien dai trong viec do dia vat ly gieng khoan
cho phep du bao di thudng ap suat d6ng thdi vdi qua trinh khoan Spery Sun
da sir dung p h u a n g phap nay tinh cho cac phep do d6ng thdi trong khi khoan
nhu sau:
Pb = ((|).Pf) + [(l-C^).((Vsh Psh) + ( 1 - V s h ) Psnd)]
Trong do: Pb la mat do t6ng, pf la mat do nude via, Psh la mat do set, Psnd la mat do
cat, (j) la do r6ng, Vsh la ty phan the tich cua set (%)
Phuong phap du bao ap suat tuc thdi da dugc ap dung cho be Nam C6n Son
nham kip thdi dieu chinh mat do dung dich khi khoan qua viing ap suat cao dugc
trinh bay tren Hinh 4 Dudng cong mau h i n g la dudng ap suit via du bao
Trang 6596 Phuong phap phat hien, xac djnh va du bao dj thudng ap suatdbeJNiim^dn^on^
Hinh 4: Dy bao ap suat tire thoi ff be Nam Con Son
b Phuong phdp dw bdo di thw&ng dp sudt theo tdi lieu dia chdn
Qua trinh nghien cim du bao di thudng ap suat d be Nam C6n Son dugc tien hanh theo cac bude nhu sau:
• Tien hanh phan tich tai lieu dia vat ly, dia chat va tai lieu gieng khoan tai cac viing da
CO gieng khoan nham phat hien va xac dinh di thudng ap suat bao g6m viec tinh toan cac th6ng s6 chuan ciia muc do nen ep binh thudng ciia be Nam C6n Son, thiet lap cac moi quan he giu:a chiing vdi ap suat via
• Phan tich tai lieu dia chan tren mat, tai vi tri c6 gieng khoan va tai viing chua khoan, xac dinh van t6c va qui luat bien d6i ciia chimg theo chieu sau va theo tuyen, phat hien cac di thudng van t6c truyen s6ng dia chan lien quan den di thudng ap suat va xay dung m6i quan he gitra van t6c truyen song va ap suat via Phan tich xu the nen ep dia chan va tfnh loan cac gia tri ap suat tir van t6c dia chan
• Chuan boa va hieu chinh cac ket qua tinh toan tir van t6c dia chan vdi tai lieu tai cac gieng khoan Loai trir anh hudng ciia cac yeu t6 dia chat khae nhau Tir do, dua ra du bao qui luat bien d6i theo chieu sau ciia ap suat via, thanh lap cac lat cat va du bao cac ddi di thudng ap suat cho nhiing viing, khu vuc chua c6 gieng khoan So d6 kh6i ciia phuong phap du bao di thudng ap suit tir tai lieu dia chan tren mat dugc trinh bay tren Hinh 5
Trang 7Tuygn tap bao cao Hdi nghj KHCN "30 nam Phu khi Vi^t Nam: Co' hoi mdi, thach thiic mdi" 597
v t i n g d a k h o a n
Tki l i e u d i a chSh trSn m a t
Tki li6u D V L G K
Tai lifiu k h o a n
A p sua't dia tTnh
ti'nh til O V L C i K
V i i n g c h u a k h o a n
T&i Hdu d i a c h ^ n trfin m a t
P/tich x u the' n e n
6D d i a c h &
A p suai via tfnh tix D V L G K
T i l l i e u thOt v i a ( D S T , R F T , L O T )
Gie'ng khoan m o i
Chuan hod, hieu chinh
Tfnh toan
a p sua't via tir
v a n t 6 c d i a cha'n
Kiem nghiem
iX
Du bao DTA,S'
=> Lap MC ^p sua't
Hinh 5: Phu'ong phap dy bao ap suat theo tai lieu dia chan tren mat
c Xdc dinh xu thi nen ep dia chdn
De tien hanh phan tich m6i quan he vdi di thudng ap suat, van t6c diem sau chung
^ A T
Cac van t6c V^sc <3ugc chuyen thanh VL theo cong thirc Dix:
V,n' = (V,lt„-Vn.,ltn.,)/(t-t„.,) Trong do: V|n la van t6c trung binh ldp thir n, Vp la van t6c diem sau chung tfnh den ldp thir n, tp la thdi gian lan truyen song den ldp thii n Neu ta lay chieu day ciia via bang don vj ta cd: AT = (1/V|) Cac nghien cim cua Chiarelli-Serra trong mdi trudng tram tich luc nguyen co miic do nen ep binh thudng da dua ra cdng thiic sau:
V = A'.e'^'^
Trong do: V la van tdc trung binh (hoae ciing cd the ap dung cho AT (1/V|)
d Tinh dp sudt via vd dp sudt phd vd via tir van tdc l&p
Sir dung cdng thirc da trinh bay:
PA = PB + (SA-SB)
vdi cac quy luat sau day:
- Log(l/V) = A + B.Z (biin dii tir c6ng thiic Chiarelli-Serra)
P = dcq|.Z/10
Ta tfnh dugc gia tri mat do tuong duong deqi(A)
Ap suit pha vd via dugc tinh theo c6ng thuc: dP = n (GG - deqi) + d^q
Trang 8598 Phuong phap ph^t hien, xac djnh va du- bao dj thudng ap suat d bg Nam^^ojljgJL
6 day, dp la gradient ap suat pha vd via, GG la gradient ap suit dia tTnh dgqi la
gradient ap suat via Trong do, hang s6 thuc nghiem (n) da dugc xac dinh dk phii hgp vdi
dilu kien dia chat cu the ciia vimg nghien cim
e Chudn hod vd kiim nghiim cdc kit qud
Ap suat via tfnh dugc tir van t6c dia chan tai cac vi tri da co gilng khoan gap di thudng ap suat dugc hieu chinh chuan boa vdi cac s6 lieu khoan cua cac gieng do Cac s6 lieu diing de chuan boa la s6 lieu khoan, cac dudng cong do DVLGK nhu sieu am, dien trd, cac s6 lieu thir via, cac s6 lieu pha vd via (LOT) S6 lieu chuan boa sau khi dugc loai trir cac anh hudng gay bdi yeu t6 thach hgc dugc sir dung de du bao cho cac gieng khoan mdi Cac kiem nghiem dugc tien hanh tren gieng khoan du bao cho biet mirc do tin cay ciia phuang phap tinh
w w
f Thdnh lap mat cdt dp sudt
Sau khi xay dimg dugc cac dudng cong bien ddi ciia ap suat via theo chieu sau tai m6i diem quet van t6c, chiing ta cd the thanh lap cac mat cat ap suat dge theo cac tuyen dia chan Day la phuong phap phan tfeh ap suat mgt each hieu qua, no cho phep kh6ng chi theo doi sir bien d6i cua ap suat via theo chieu sau ma cdn cd the theo ddi cac thay d6i nay theo tuyen
4 Mot so ket qua dy bao di thirdng ap suat
Hinh 6 bieu dien ket qua du bao che do ap suat via tai mgt dia diem c6 gieng khoan
du kien vdi muc nude bien la 50m, d 16 04 be Nam C6n Son Cot thir nhat la cot dia tang dugc thanh lap tir ket qua minh giai dia chan Cot thii hai m6 ta dudng AT tinh tir van t6c dia chan, tren do t6n tai hai dj thudng van t6c dia chan d cac do sau 1850 - 2050m va 2750
- 3100m, la co sd de xac dinh su bien d6i cua cac loai ap suat theo chieu sau d cot thir tu Hinh 7 m6 ta viec chuan boa cac ket qua xac dinh di thudng ap suat theo van t6c dia chan vdi tai lieu DVLGK Cac gia tri ap suat tinh theo sieu am va van toe dia chin la kha dong dang vdi sir thay d6i ciia dudng cong dien trd
Hinh 8 trinh bay ket qua kiem nghiem do chinh xac ciia phuang phap du bao di thudng ap suat trudc khi khoan vdi tai lieu sau khi da khoan dugc Kit qua so sanh cho thay: viec co di thudng ap suat la diing vdi du bao; sai s6 la 50m d viing chua c6 di thudng
va < 50m 6 viing xuat hien di thudng, do chinh xac ciia viec du bao ap suit pha vd via va s6 lieu thir do cimg ciia via (LOT) co sai s6 vao khoang 1 PPG (~ 0,12SG)
Hinh 9 trinh bay mgt mat cit ap suit d 16 04 co hudng Tay BIC - Ddng Nam cit ngang phan phia Bae ddi nang Dai Hiing - Mang Clu Tai khu vuc nay tdn tai cac trim tich Miocen - Pliocen rat day Nghien ciiu mat cit nay cho thay vimg di thudng ap suit cao xuat hien hau het dge theo tuyen dia chin rli sau do giam d phan cu6i tuyin (hudng D6ng Nam) nhu la he qua cua viec giam chilu day trim tich Dudng d6ng mirc 12PPG dugc coi nhu la bat dau cua ddi ap suit cao Trong do dudng d6ng mirc 14PPG dugc xem nhu la viing ap suat cao nguy hiim
Trang 9Tuygn tap bao cao Hdi nghj KHCN "30 nam D5u khi Viet Nam: Co" hpi mdi, thach thuc mdi" 599
Dir KIEN CHLTONG TRINH KHOAN
Ap suit tinh tir dia chan (Gradien - 10 kG/cm^/m)
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Hinh 6: Dy bao ve ap suat via va ap suat pha vd via tai mot dilm dy kien khoan
ff 16 04, Nam Con Son
Trang 10600 Phuong phap phat hien, xac djnh va dy bao dj thudng ap suat d bg Nam Cdnjoji^
jt r
CHUAN HOA VOI TAI LIEU DVLGK
•500
1000
1500
2000
2500
ai
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i
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Hinh 7: Hieu ehinh chuan hoa vdi tai lieu DVLGK be Nam Con Son