Kusanthula kwa Zinthu Zambiri mu Kufufuza kwa Chilengedwe
Kufufuza za seismic kwakhala kudziwika kwambiri ngati njira yayikulu yopangira mapu a zomangamanga za pansi pa nthaka kwa zaka zambiri, makamaka m'mafakitale a mafuta ndi gasi, geothermal, ndi engineering geology. Mwachizolowezi, deta ya seismic nthawi zambiri imalembedwa ngati mafunde okakamiza kapena ma P-wave okha. Komabe, kupita patsogolo kwa ukadaulo wopeza zinthu komanso kufunikira kotanthauzira mwatsatanetsatane kwalimbikitsa kugwiritsa ntchito deta ya seismic ya magawo ambiri—kutanthauza kulemba magawo oposa limodzi a kayendedwe ka nthaka—kuti ipeze yankho labwino kwambiri la pansi pa nthaka. Kusanthula kwa magawo ambiri tsopano ndi njira yofunika kwambiri yomvetsetsa lithology, madzi a pore, anisotropy, komanso makhalidwe osweka, zomwe zonse zimakhala zovuta kuzijambula ndi deta ya seismic ya gawo limodzi.
Malingaliro Oyambirira a Chisinthiko Chazigawo Zambiri
Mawu akuti multicomponent nthawi zambiri amatanthauza kujambula kayendedwe ka tinthu m'njira zosiyanasiyana. Mu kafukufuku wa nthaka, ma geophone a magawo atatu (3C) amalemba kayendedwe m'njira yowongoka (Z) ndi njira ziwiri zopingasa (X ndi Y). Panyanja, kujambula kwa tinthu tambiri kumachitika pogwiritsa ntchito masensa a chingwe cha pansi pa nyanja (OBN/OBS) omwe amayesa kuthamanga kwa mpweya (hydrophones) ndi liwiro la tinthu (geophones), zomwe zimapereka zambiri zowonjezera kuti zigwiritsidwe ntchito komanso kumasuliridwa.
Mafunde ofunikira kwambiri a chivomerezi pankhaniyi ndi ma P-wave ndi ma S-wave. Ma P-wave amafalikira kudzera mu kupsinjika ndi kukulitsa kwa medium, pomwe ma S-wave amakhudza kudulidwa. Ma S-wave ali ndi njira ziwiri za polarization (SV ndi SH) zomwe mayankho ake ndi ofunikira kwambiri ku anisotropy ndi fracturing. Chifukwa cha chibadwa chawo chakuthupi, ma S-wave sangafalikire kudzera mu madzi oyera, kotero yankho lawo limayimira kwambiri chimango cha miyala kuposa madzi a pore. Kusiyana kumeneku kwa sensitivity ndi komwe kumapangitsa kusanthula kwa multicomponent kukhala kokongola: kuphatikiza kwa chidziwitso cha P ndi S kumathandizira kuthekera kosiyanitsa mawonekedwe a miyala.
Mitundu ya Deta mu Multicomponent Seismic
Mu kafukufuku, mitundu ina ya deta ya zinthu zambiri yomwe imasanthulidwa nthawi zambiri ndi iyi:
1. PP (P-to-P): Mafunde a P amawonetsedwa ndikulembedwa ngati P, ofanana ndi chivomerezi chachikhalidwe.
2. PS (P-to-S): Mafunde a P omwe, akamawunikira/kusintha, amasintha kukhala mafunde a S ndipo amalembedwa pa gawo lopingasa. Deta ya PS nthawi zambiri imatchedwa kuti converted-wave seismic.
3. SS (S-to-S): Mafunde a S omwe amawonetsedwa ngati S, nthawi zambiri amafunikira gwero la mafunde a S (lomwe limapezeka kwambiri pamtunda ndi maphunziro apadera).
4. Mafunde a pamwamba ndi njira zoyendetsera mafunde: Monga Love/Rayleigh, zomwe nthawi zina zimaonedwa ngati phokoso koma zingagwiritsidwenso ntchito pofotokoza zinthu zosaya kwambiri.
Deta ya PS ndi yamtengo wapatali chifukwa ingapezeke ndi magwero wamba a P (monga vibroseis kapena airguns), pomwe zolandirira za 3C zimalola kujambula zigawo za S zomwe zasinthidwa.
Kupeza: Mavuto ndi Chinsinsi cha Kupambana
Kupambana kwa kusanthula kwa zinthu zambiri kumadalira kwambiri mtundu wa kupeza. Pa nthaka, kuyang'ana kwa sensor yopingasa ndikofunikira: zolakwika za geophone azimuth zimatha kubisa polarization ya S-wave ndikupangitsa kusanthula kwa anisotropy kukhala kovuta. Kulumikizana kwa sensor pansi, zovuta zomwe zili pafupi ndi pamwamba, komanso kusinthasintha kwa static kumabweretsa zovuta zina.
Panyanja, kugwiritsa ntchito OBS/OBN kuli ndi ubwino wokhoza kujambula gawo la mafunde lokwanira, koma kumawonjezera zovuta pakukonza: momwe sensa imayendera pansi pa nyanja iyenera kuyerekezeredwa, mphamvu yamagetsi/yopendekeka iyenera kukonzedwa, ndipo kulekanitsidwa kwa mafunde a P ndi S kumafuna njira zapadera monga kulekanitsidwa kwa mafunde.
Kuphatikiza apo, mapangidwe a kafukufuku wazinthu zambiri nthawi zambiri amaona kuti azimuth imafalikira bwino, chifukwa kusanthula kwa anisotropy (monga anisotropy yomwe imayambitsa kusweka) kumathandizidwa kwambiri ndi kusiyana kwa azimuth.
Kukonza Deta kwa Zigawo Zambiri
Kukonza zinthu zambiri sikungowonjezera njira za deta. Gawo lililonse lokonza limafuna kuganizira kusiyana kwa fizikiki ya kufalikira kwa P ndi S. Masitepe ena ofunikira ndi awa:
1. Kusinthasintha kwa Zigawo ndi Kuwongolera
Mu deta ya 3C, zigawo zopingasa (X, Y) nthawi zambiri zimafunika kuzunguliridwa kukhala dongosolo lolumikizirana la radial-transverse poyerekeza ndi komwe gwero likupita. Kuzungulira kumeneku kumathandiza kulekanitsa mphamvu ya SV ndi SH, makamaka mu deta ya PS. Mu nyanja, momwe ma geophone a pansi pa nyanja amayendera nthawi zambiri samadziwika bwino ndipo motero amafunika kuyerekezeredwa kuchokera ku chizindikiro (monga, pogwiritsa ntchito njira yolamulira ya polarization ya P-wave).
2. Kulekana kwa Wavefield
Cholinga cha sitepe iyi ndikulekanitsa mphamvu ya pamwamba ndi pansi, ndikulekanitsa zigawo za P ndi S nthawi iliyonse yomwe zingatheke. Mu OBC/OBS, kuphatikiza kwa ma hydrophone ndi ma geophone kumalola kulekanitsa mafunde akumtunda ndi pansi, kuchepetsa kuchulukana ndikuwongolera khalidwe la chithunzi.
3. Kukonza Kosasunthika ndi Pafupi ndi Pansi
Mafunde apafupi ndi pamwamba nthawi zambiri amayambitsa kusokonekera kwakukulu mu ma S-wave chifukwa cha liwiro lawo lotsika komanso kukhudzidwa kwakukulu ndi kusiyana kosaya. Static S nthawi zonse si yofanana ndi static P, kotero kukonza PS kumafuna njira zapadera, monga kuyerekezera nthawi yofika kwa ma S-wave obwezeretsedwa kapena njira yosinthira pafupi ndi pamwamba.
4. Kusanthula kwa Liwiro ndi Kusuntha
Liwiro la S ndi laling'ono kuposa P, kotero nthawi yoyenda ya PS ndi yayitali. Kusuntha mu PS sikofanana chifukwa njira za P ndi S ndizosiyana. Kusankha chitsanzo cha liwiro la kujambula kwa PS (monga VPS kapena chiŵerengero cha Vp/Vs) ndikofunikira kuti tipewe kuyika molakwika chowunikira.
5. Kusamuka kwa PS ndi Kulembetsa Zochitika
Kusamuka kwa PS nthawi zambiri kumachitika pogwiritsa ntchito njira yosinthira mafunde osinthika pogwiritsa ntchito mitundu ya Vp ndi Vs. Kulembetsa zochitika nthawi zambiri kumachitika pambuyo pake kuti ziwonetsedwe za PP ndi PS zigwirizane pamalo omwewo. Kusamuka kumeneku ndikofunikira pakuwunika kwa zizindikiro zolumikizana komanso kusintha.
6. Kukonza Anisotropy ndi Kugawanitsa Mawave ndi Shear-Wave
Mu anisotropic media, ma S-wave amatha kugawikana m'mafunde awiri ozungulira omwe ali ndi liwiro losiyana (kugawikana kwa mafunde a shear-wave). Kusanthula kwa kugawikana kungagwiritsidwe ntchito kuyerekeza komwe kumayambira kugawikana ndi kuchuluka kwa anisotropy. Izi ndizothandiza makamaka m'malo osungira carbonate osweka kapena ma anisotropic shales.
Kutanthauzira ndi Mapindu Aakulu
Kusanthula kwa zinthu zambiri kumatsegula mwayi wochuluka wotanthauzira kuposa deta ya PP yokha:
1. Kuyerekeza kwa Vp/Vs ndi Chizindikiro cha Lithology-Fluid
Chiŵerengero cha Vp/Vs ndi chizindikiro chodziwira matenda chomwe chimakhudzidwa ndi lithology ndi kuchuluka kwa madzi. Kawirikawiri, mpweya ukhoza kutsika kwambiri Vp kuposa Vs, kotero Vp/Vs nthawi zambiri imachepa m'malo osungira mpweya (ngakhale kutanthauzira kuyenera kusamala komanso kutsatiridwa). Mwa kuphatikiza chidziwitso cha PP ndi PS, omasulira amatha kupanga mamapu a Vp/Vs omwe amathandiza kusiyanitsa pakati pa madera osungira mchenga ndi matope kapena odzaza ndi mpweya poyerekeza ndi madera osungira madzi.
2. Kufotokozera za Ming'alu ndi Kupsinjika Maganizo
Kugawanika kwa mafunde a shear ndi kusintha kwa azimuthal mu yankho la PS kungasonyeze momwe mafunde akusweka komanso komwe kuli mphamvu yayikulu yopingasa. Izi ndizothandiza pakukonza chitsime chopingasa, kusonkhezera madzi, kapena kupanga chitsanzo cha mphamvu ya malo osungira madzi osweka.
3. Kujambula Pansi pa Gasi kapena Basalt Zone
M'madera ena, zithunzi za PP zimawonongeka chifukwa cha kuchepa kapena kufalikira (monga, pansi pa malo osaya a gasi kapena basalt). Kusintha kwa mafunde a PS nthawi zina kumapereka chithunzi china chifukwa cha kusinthasintha kwake. Ngakhale PS imakhalanso ndi zovuta (kuchepa kwa pafupipafupi, phokoso lalikulu), pansi pa mikhalidwe ina imatha kuwulula kapangidwe kobisika mu PP.
4. Makhalidwe ndi Kusinthasintha kwa Zinthu Zambiri
Kuphatikiza kwa makhalidwe a PP ndi PS kumalola kuti pakhale kusinthasintha kwa elastic: osati kokha kwa acoustic impedance (AI) ya P-wave, komanso shear impedance (SI) ndi magawo ena otanuka monga chiŵerengero cha Poisson kapena Lambda-Rho ndi Mu-Rho (pansi pa malingaliro ena). Izi zimalimbitsa kusanthula kwa rock physics ndi kulosera za facies.
Zofooka ndi Zovuta Zogwira Ntchito
Ngakhale kuti pali zabwino zambiri, chivomerezi cha zinthu zambiri chili ndi zofooka zingapo:
- Mtengo wokwera komanso zovuta (zipangizo za 3C, OBN/OBS, zofunikira za QC zovuta).
- Ubwino wa deta ya S/PS nthawi zambiri umakhala wotsika kuposa PP chifukwa cha phokoso, kulumikizana, komanso bandwidth yocheperako.
- Kukonza kovuta kwambiri: static S, anisotropy, ndi kufunikira kwa mitundu ya Vp ndi Vs yofanana.
- Kutanthauzira kumafuna kuphatikiza ndi deta ya zitsime, fizikisi ya miyala, ndi geology kuti tipewe mayankho osakhala apadera.
Chifukwa chake, zinthu zambiri zimakhala zabwino kwambiri zikakonzedwa kuyambira pachiyambi: zolinga za geological zimakhala zomveka bwino (monga mapu a fracture, Vp/Vs prediction), kapangidwe ka kugula kamathandizira azimuth, ndipo pulogalamu yokonza zinthu imaganizira kale zosowa zomasulira.
Kutseka
Kusanthula kwa zinthu zambiri mu kufufuza kwa seismic ndi njira yomwe imakulitsa zenera lowonera pansi pa nthaka pogwiritsa ntchito chidziwitso kuchokera ku mitundu yoposa imodzi ya mafunde ndi kayendetsedwe ka tinthu. Mwa kuphatikiza deta ya PP ndi PS, ndikugwiritsa ntchito mphamvu zobisika za ma S-wave ku maziko a miyala, anisotropy, ndi kusweka, kusanthula kwa zinthu zambiri kungathandize kumvetsetsa bwino za lithology, madzi, ndi mikhalidwe yopsinjika. Ngakhale kumafuna kupeza ndi kukonza zinthu zovuta kwambiri, phindu lake lowonjezera ndilofunika kwambiri pa zolinga zovuta komanso zosowa zapamwamba zowunikira malo osungiramo zinthu. Pankhani ya kufufuza kwamakono, komwe kumafuna kuchita bwino komanso kulondola zisankho, kugwedezeka kwa zinthu zambiri kumaonedwa ngati chida chofunikira kwambiri chochepetsera kusatsimikizika ndikukweza mtundu wa kutanthauzira kwa pansi pa nthaka.
