Ukuqonda okuyisisekelo kwe-anisotropy yokuzamazama komhlaba
I-Seismic anisotropy ingumqondo obalulekile ku-geophysics ochaza ukuthi kungani amagagasi e-seismic engahamba ngesivinini esihlukene edwaleni, kuye ngokuthi ahamba kanjani kanye/noma i-polarization. Kumamodeli amaningi okuqala, uMhlaba wawuvame ukucatshangwa ukuthi uyi-isotropic - okusho ukuthi izakhiwo zawo ezinwebekayo ziyafana kuzo zonke izinhlangothi. Kodwa-ke, empeleni, ungqimba loMhlaba kanye ne-mantle kuvame ukubonisa izakhiwo ze-anisotropic ngenxa yesakhiwo sangaphakathi samatshe, ukuqondiswa kwamaminerali, ukuqhekeka, kanye nokucindezeleka okusetshenzisiwe. Ukuqonda i-seismic anisotropy kusiza ekuchazeni idatha ye-seismic, kuthuthukisa ukunemba kwezithombe ezingaphansi komhlaba, futhi kunikeza izinkomba zezinqubo ze-geological ezifana nokuguquguquka, ukugeleza kwe-mantle, noma izinhlelo zokuqhekeka ezindaweni zokugcina amanzi.
1. Imiqondo eyisisekelo: i-isotropy vs i-anisotropy
Ku-isotropic medium, ijubane lamagagasi okuzamazama komhlaba lincike kuphela ohlotsheni lwegagasi (P noma S) kanye namapharamitha okuma kwe-medium (isb., i-bulk modulus, i-shear modulus, kanye nobuningi), hhayi ohlangothini lokusabalala. Ngokuphambene nalokho, ku-anisotropic medium, izakhiwo zokuma ziyahlukahluka ngokuya ngokuqondisa. Ngenxa yalokho, amagagasi e-P kanye ne-S angabhekana nokwehluka kwejubane nge-azimuth (isiqondiso esivundlile) noma nge-engeli yokwenzeka maqondana nengqimba/isakhiwo sedwala.
I-anisotropy yokuzamazama komhlaba akusho ukuthi idwala "lihlukile ngokwesakhiwo" ukusuka kolunye uhlangothi kuya kolunye, kodwa kaningi kusho ukuthi idwala linesakhiwo esincane nesibanzi, isibonelo i-lamination, i-foliation, i-mineral grain orientation, noma inethiwekhi yokuqhekeka ebusa ohlangothini oluthile.
2. Izimbangela eziyinhloko ze-anisotropy yokuzamazama komhlaba
Kunezindlela eziningana ezivamile ze-geological eziyimithombo ye-anisotropy:
1. Ukwendlalela okuncane
Ezikalini ezincane kunobude be-wavelength yokuzamazama komhlaba, izendlalelo ezincane ezinezakhiwo ezihlukene zokunwebeka zingabonakala ngamagagasi njengendlela ephumelelayo ye-anisotropic. Lokhu kuvame ukuba njalo ezindaweni ezinezingqimba.
2. Ukuqondiswa kwamaminerali (ukuqondiswa okuthandwayo kwekristalografikhi / i-CPO)
Emaphethelweni, amaminerali afana ne-olivine angahambisana nokuma okunamandla ngenxa yokuguquguquka nokugeleza. Le CPO ikhiqiza i-anisotropy enamandla, evame ukutholakala ngokuhlukana kwe-S-wave.
3. Ukuqhekeka okuqondiswe ezinhlangothini kanye nezindawo ezimboziwe (i-anisotropy ebangelwa ukuqhekeka)
Ema-hydrocarbon, geothermal, noma ama-crystalline reservoirs, amasethi okuqhekeka aqondiswe ngqo angadala ukwehluka okuqondiswe ngqo ejubaneni lamagagasi. Lolu hlobo lwe-anisotropy lubaluleke kakhulu ekuchazeni ukuqhekeka kanye nokubikezela ukuvuleka okuqondiswe ngqo.
4. Ukucindezeleka okungaphakathi (i-anisotropy ebangelwa ukucindezeleka)
Ngisho noma kungekho ukuqhekeka okusobala, ukucindezeleka kungathinta ukuvulwa kwe-microcrack kanye nokuxhumana phakathi kwe-granular, okuholela empendulweni ye-anisotropic. Lesi simo sibalulekile ekuqapheni ukukhiqizwa kwe-geomechanics kanye nokuqapha ukukhiqizwa kwedamu.
3. Izimpawu kanye nokubonakaliswa kwe-anisotropy kudatha yokuzamazama komhlaba
I-Anisotropy ingabonakala ngezindlela eziningana zokubuka:
- Ukwehluka kwejubane maqondana nesiqondiso (ijubane eliqondisa indlela)
Isibonelo, amagagasi e-P ahamba ngokushesha ahambisana nezingubo zokulala kunama-perpendicular nezingubo zokulala emadwaleni e-sedimentary ahlanganisiwe.
- Ukuhlukana kwe-Birefringence noma i-shear-wave
I-S-wave engena endaweni ye-anisotropic ingahlukana ibe ama-S-wave amabili aqondile (avame ukubizwa ngokuthi i-fast-S kanye ne-slow-S), ngezikhathi ezahlukene zokufika (ukubambezeleka kwesikhathi). Isiqondiso se-fast-S polarization sivame ukuhlobana nokuqondiswa kokuqhekeka noma isiqondiso sokucindezeleka okunamandla.
- Ukuhamba kwe-Anisotropic kudatha yokuzindla
Ekushukumeni kokukhanya, i-anisotropy ithinta ubudlelwano phakathi kwesikhathi sokuhamba kanye ne-offset (ibanga lomthombo-owamukelayo). Uma kunganakwa, ukucubungula njengokulungiswa kwe-NMO, ukuqoqa inqwaba, kanye nokufuduka kungaveza izithombe ezisontekile noma ezifiphele.
– I-AVO/AVA (ukwehluka kwe-amplitude ngezinguquko ze-offset/engela)
I-Anisotropy ingashintsha futhi impendulo ye-amplitude ku-engeli ye-incidence, ukuze ukuhumusha kwe-lithology kanye noketshezi kungachemile lapho kusetshenziswa izibikezelo ze-isotropic.
4. Izinhlobo ze-anisotropy ezivame ukusetshenziswa ku-geophysics
Ngenxa yokuthi i-anisotropy emvelweni ingaba yinkimbinkimbi kakhulu, izazi ze-geophysicists zivame ukusebenzisa imodeli yokwenza kube lula:
1. I-VTI (I-Vertical Transverse Isotropy)
Ibizwa nangokuthi i-TI ene-axis eqondile yokulinganisa. Le modeli ifanelekela izihlabathi ezinezingqimba ezivundlile: izakhiwo zale medium ziyi-isotropic endizeni evundlile, kodwa ziyahlukahluka ohlangothini oluvundlile. I-VTI ivame kakhulu ekuhlolweni kwe-seismic.
2. I-HTI (I-Isotropy Evundlile Evundlile)
I-TI ene-axis evundlile yokulinganisa ivame ukusetshenziswa ukumela imidiya enezimfa eziqondile ezihambisana nesiqondiso esithile. Le modeli isetshenziswa kabanzi ekuhlaziyeni ukuphuka.
3. I-TTI (I-Tilted Transverse Isotropy)
Kufana ne-TI, kodwa i-axis of symmetry ithambekile. I-TTI ibalulekile ezingqimbeni ezigoqiwe noma ezakhiweni eziyinkimbinkimbi njengamaphiko e-anticline, amaphutha, kanye nezindawo zokuphonsa.
4. I-anisotropy ye-Orthorhombic
Okuyinkimbinkimbi kakhulu, inezimbazo ezintathu eziqondile ezinezakhiwo ezahlukene. Ingamelela inhlanganisela yezendlalelo eziqondisiwe kanye nokuqhekeka. Le modeli isetshenziswa kakhulu ezifundweni zanamuhla ngenxa yemvelo yayo engokoqobo, yize ukwakheka kwayo kanye nokuguqulwa kwayo kuyinselele kakhulu.
5. Amapharamitha e-Anisotropy: imibono eyisisekelo
Ekuhlolweni, i-TI anisotropy ivame ukubekwa ngamapharamitha nge-Thomsen parameters (ε, δ, γ) ye-anisotropy ebuthakathaka. Ngaphandle kokungena ezibalweni ezijulile, umqondo oyinhloko uwukuthi:
– ε ihlobene nomehluko wejubane le-P-wave endaweni evundlile uma kuqhathaniswa nesiqondiso esiqondile (ku-VTI).
– i-δ ithinta ukuziphatha kwamagagasi e-P kuma-engeli aphakathi (cishe aqonde phezulu kuya ema-engeli aphakathi), kubalulekile ekuphumeni.
– i-γ ihlobene ne-anisotropy yamagagasi e-S (ikakhulukazi engxenyeni ye-SH) futhi ithonya amagagasi e-shear.
Lezi zinhlaka zisiza ukulungisa ukuhamba, ukuthuthukisa ukufuduka, futhi zihlobanise impendulo yokuzamazama komhlaba ezakhiweni ze-geological ezifana ne-lamination noma ukuqhekeka.
6. Izindlela zokulinganisa nokuhumusha i-anisotropy
I-anisotropy ye-seismic ingalinganiswa ngezinhlobo ezahlukene zedatha:
1. Ukuhlukaniswa kwamagagasi okusika
Ilinganisa isiqondiso se-fast-S kanye nokubambezeleka kwesikhathi. Isetshenziswa kabanzi kwi-earthquake seismology ukutadisha ukugeleza kwe-mantle kanye nesiqondiso sokucindezeleka kwe-crustal, kanye nasezinhlolovo ze-3D eziningi zama-reservoirs.
2. Ukuhlaziywa kwe-azimuthal kokubonakaliswa kokuzamazama komhlaba
Idatha ihlukaniswe yi-azimuth (isb., imikhakha eminingana ye-azimuth), bese ihlaziywa ukuze kutholakale umehluko wejubane/ukunyakaza/ukuphakama. I-HTI kanye ne-orthorhombic kuvame ukuhlolwa kusukela kulezi zinguquko.
3. Isithombe sokuhlola/i-VSP kanye nelogi lomthombo
Idatha ye-Well inikeza ukulawula ukujula futhi ingalinganisa ngokunembile ijubane eliqondile. Kwezinye izimo, izilinganiso zokuloba ze-sonic dipole zingathola izinkomba ze-S-wave anisotropy kanye nokuqhekeka.
4. Ilebhu yefiziksi yamadwala
Amasampula ayinhloko ahlolwe ukuze kutholakale ama-constant elastic kanye nempendulo ye-anisotropic, okusiza ukuhlobanisa idatha yokuzamazama komhlaba nezakhiwo zomzimba ezingaphansi.
7. Kungani i-anisotropy ibalulekile ekucutshungulweni nasekuthathweni kwezithombe zokuzamazama komhlaba?
Ukungazinaki i-anisotropy kungabangela izinkinga eziningana ezisebenzayo:
– Iphutha lokunquma imodeli yejubane elibangela ukujula okungalungile kwesibukisi.
– Izithombe zokufuduka azigxili kakhulu ikakhulukazi ezindaweni ezinezendlalelo ezithambekele noma izakhiwo eziyinkimbinkimbi.
– Ukuchazwa kabi kwe-AVO ngoba izinguquko ku-amplitude zingaphanjaniswa nemiphumela yoketshezi/i-lithology kuyilapho empeleni zithonywa yi-anisotropy.
– Ukwehluleka ukudweba ama-fracture uma ukuhlukahluka kwe-azimuthal kungahlaziywanga kahle.
Ngokufaka i-anisotropy, amamodeli ejubane kanye nokufuduka (isb., ukufuduka kwe-TTI) angakhiqiza izithombe ezibukhali kanye nezindawo zokubonisa ezinembile, okuthuthukisa ukuthembeka kokuchazwa kwe-geological.
8. Izinselele kanye nemikhawulo
Nakuba kuwusizo, i-anisotropy yokuzamazama komhlaba nayo iletha izinselele:
– Okungeyona eyingqayizivele (ukungacaci): ukuhlanganiswa kwamapharamitha amaningana kungaveza izimpendulo zedatha ezifanayo.
– Ikhwalithi ye-Azimuthal kanye nokumbozwa kwayo: ukulinganiswa kwe-azimuthal anisotropy kudinga i-geometry yokutholwa efanele.
– Isikali: i-anisotropy ebonakala ku-seismic iyindlela ephumelelayo ye-anisotropy esikalini se-wavelength, hhayi ngempela i-anisotropy encane.
– Ubunzima be-Geological: ezindaweni eziyinkimbinkimbi zamaphutha, imodeli elula ye-TI ivame ukunganeli.
Ngakho-ke, incazelo ye-anisotropy kufanele ihlale ihlotshaniswa nolwazi lwe-geological, idatha yemithombo, kanye nokuqonda i-physics yamadwala.
9. Isiphetho
Ukuqonda okuyisisekelo nge-anisotropy yokuzamazama komhlaba kuvela eqinisweni lokuthi uMhlaba awuhlali u-isotropic. Ukwehlukaniswa, ukuqhekeka, ukuqondiswa kwamaminerali, kanye nokucindezeleka kungabangela amagagasi okuzamazama komhlaba ukuba asakazeke ngezindlela ezahlukene, okubangela izimo ezifana nokushintshashintsha kwejubane, ukuhamba kwe-anisotropic, kanye nokuhlukana kwamagagasi. Ekuhloleni kanye ne-seismology, i-anisotropy akuyona nje "ukulungiswa kobuchwepheshe," kodwa futhi iwindi lezinqubo ze-geological: isiqondiso sokuguquguquka, izinhlelo zokuqhekeka, kanye ne-mantle dynamics. Ngemodeli efanele (i-VTI, i-HTI, i-TTI, noma i-orthorhombic) kanye nokuhlanganiswa kwedatha okuhle, i-anisotropy yokuzamazama komhlaba ingathuthukisa ukunemba komfanekiso we-subsurface ngenkathi icebisa ukuchazwa kwesakhiwo sedwala kanye nezakhiwo.
Uma ufisa, ngingangeza isigaba esifushane esinezibonelo zamacala (isb., i-VTI anisotropy ku-shale enezingqimba noma i-HTI ezindaweni zokugcina amanzi eziqhekekile) noma ngifake umfanekiso womqondo wokuhlukaniswa kwamagagasi e-shear kanye namapharamitha e-Thomsen ngesimo sethebula.
