Neutron logging. Zoo kaw txoj kev

2024 Tus sau: Howard Calhoun | [email protected]. Kawg hloov kho: 2023-12-17 10:28

Neutron logging thiab nws ntau yam muaj nyob rau hauv cov txheej txheem hluav taws xob ntawm kev tshawb fawb geophysical. Nyob ntawm seb hom hluav taws xob kuaj pom (neutrons lossis gamma photons), muaj ntau qhov kev hloov kho ntawm cov thev naus laus zis no. Cov khoom siv Downhole muaj qhov zoo sib xws. Neutron logging ua rau nws muaj peev xwm txiav txim siab ib qho ntawm cov cim tseem ceeb tshaj plaws ntawm kev tsim cov roj thiab roj - cov porosity coefficient, nrog rau kev faib cov dej ntws los ntawm cov kua dej uas muaj nyob hauv lawv.

Txoj kev tshawb fawb geophysical

Hauv geophysics, ntau txoj hauv kev rau kev kawm pob zeb yog siv, uas tuaj yeem muab faib ua 2 pawg loj: hluav taws xob (electromagnetic) thiab tsis yog hluav taws xob. Thawj pawg suav nrog cov hauv qab no:

• Tshawb nrhiav nrog cov kev sojntsuam tsis pom zoo: o txoj kev pom kev tiv thaiv; o microprobing; o resistivity; o cov ntaub ntawv tam sim no.
• Kev sojntsuam tsom mus rau txoj hauv kev: olateral txiav; o divergent logging.
• Electromagnetic techniques: o induction logging; o yoj electromagnetic logging; o downhole xov tooj cua yoj txoj kev.
• Txoj kev ntsuas kev ua haujlwm electrochemical: o spontaneous orientation tej zaum txoj kev; o txoj kev ntawm electrode muaj peev xwm; o evoked tej zaum txoj kev.

Pab pawg thib ob suav nrog cov thev naus laus zis hauv qab no:

• Seismoacoustic txoj kev: o acoustic logging (xws li xav yoj txoj kev); o ntsug zoo profileing; o cross-zoo acoustic transillumination; o seismic.
• Nuclear physics method.
• Thermal logging.
• Magnetic research method: o borehole magnetic prospecting; o magnetic susceptibility logging; o nuclear magnetic logging.
• Downhole gravity exploration.
• Gas thiab mechanical logging.

Radiometric method

Nuclear physics txoj kev tshawb fawb suav nrog ntau pab pawg thev naus laus zis:

• gamma ray logging (kev ntsuas ntawm cov hluav taws xob ntuj);
• gamma-gamma-method;
• neutron method;
• tagged atom technology;
• ua kom gamma txoj kev.

Cov txheej txheem no yog cov cuab yeej muaj zog rau kev kawm txog geological formations intersected los ntawm lub qhov dej. Lawv ua raws li kev ntsuas qhov ntsuas ntawm ionizing hluav taws xob tawm los ntawm cov nuclei ntawm atoms ntawm cov khoom muaj nyob hauv pob zeb. Zoo li acoustic logging, radiometric txoj kevtuaj yeem muab faib ua cov qauv uas ntsuas qhov ntuj thiab cov khoom siv hluav taws xob (kua hluav taws xob). Raws li cov khoom siv hluav taws xob, cov uas muaj lub zog nkag siab tshaj plaws yog siv - neutrons (n) thiab gamma quanta.

Qhov tseem ceeb ntawm neutron technologies

Neutron logging yog ib txoj hauv kev ntawm kev tshawb fawb geophysical, uas yog ua raws li qhov cuam tshuam ntawm lub nrawm neutron flux. Raws li qhov tshwm sim, lawv tau qeeb qeeb, tawg thiab nqus rau hauv pob zeb.

Downhole sojntsuam rau kev txiav neutron muaj cov hauv qab no tseem ceeb:

• xov tooj cua hluav taws xob;
• particle txee (n lossis gamma quanta);
• filters uas tsis suav cov hluav taws xob ncaj qha los ntawm qhov chaw mus rau qhov ntsuas.

Neutron yam ntxwv ntawm pob zeb

Thaum ntaus pob zeb, cov neutrons nrawm nrawm thiab poob zog vim muaj kev cuam tshuam nrog atoms. Nyob rau hauv lub xeev no, lawv dissipate nyob rau hauv cov teeb meem thiab raug ntes los ntawm lub nuclei ntawm atoms ntawm cov tshuaj nyob rau hauv feem ntawm milliseconds.

Tus neeg mob hnyav tshaj plaws yog hydrogen. Txoj kev luv luv uas cov neutron taug kev ua ntej mus txog lub xeev thermal yog cov yam ntxwv ntawm cov pob zeb uas muaj cov ntsiab lus hydrogen siab (roj- thiab dej-saturated reservoirs, minerals, uas muaj dej ntau ntawm crystallization).

Cov yam ntxwv hauv qab no neutron ntawm pob zeb yog qhov txawv:

1. Txoj kev qeeb qeebneutrons mus rau lub xeev thermal (nyob rau hauv uas lub zog ntawm ib tug particle mus txog tus nqi ntawm qhov nruab nrab kinetic zog ntawm thermal motion ntawm molecules thiab atoms ntawm lub pob zeb).
2. Diffusion ntev (txoj kev los ntawm qhov chaw ntawm qhov pom ntawm thermal neutron rau nws qhov nqus).
3. Lub neej ntawm cov khoom hauv lub xeev thermal.
4. Txoj kev ntsuas hauv pob zeb.
5. Particle migration length (tag nrho cov kev ncua deb mus thaum lub sij hawm deceleration thiab diffusion).

Hauv kev xyaum, cov khoom no raug soj ntsuam siv cov xwm txheej neutron porosity coefficient.

Ntau yam

Neutron logging suav nrog ntau hom kev tshawb fawb uas txawv hauv 2 lub ntsiab lus tseem ceeb:

• Radiation qhov chaw ua haujlwm hom: o txoj hauv kev ruaj khov; o txoj kev impulse (siv mas tom qab zoo casing).
• Qhov xwm txheej ntawm cov hluav taws xob thib ob uas tau sau tseg: o n-neutron logging (ntsuas tus naj npawb n ntawm cov pob zeb uas tawg los ntawm atomic nuclei); o neutron gamma method (ɣ hluav taws xob tshwm sim los ntawm kev ntes ntawm n); o neutron activation logging (ɣ-kib hluav taws xob ntawm cov khoom siv radionuclides tso tawm thaum nqus ntawm n).

Kev hloov pauv kev txiav txim siab feem ntau yog nyob ntawm hom ntsuas (helium, scintillation, semiconductor counters) thiab cov ntxaij lim dej ib puag ncig. Cov txheej txheem nyob ruaj ruaj tau suav nrog hauv cov kev tshawb fawb uas yuav tsum tau ua thaum drilling qhov dej tshawb nrhiav.

Neutron-neutron cov txheej txheem

Txoj kev tshawb fawb geophysical no yog ua raws li thawjneutron yam ntxwv ntawm pob zeb thiab muaj 2 ntau yam: sau npe ntawm thermal lossis epithermal neutrons. Lub zog ntawm lub tom kawg yog me ntsis ntau dua lub thermal zog ntawm atoms.

Hydrogen ntawm tag nrho cov ntsiab lus yog anomalous tsis tsuas yog nyob rau hauv cov nqe lus ntawm tawg geometry, tab sis kuj nyob rau hauv cov nqe lus ntawm lub zog poob ntawm ib tug neutron thaum sib tsoo nrog nws. Gas reservoirs yog tus cwj pwm los ntawm kev nyeem ntawv siab dua li dej- thiab roj-saturated reservoirs, vim hais tias cov ntsiab lus hydrogen hauv lawv qis dua.

Qhov ntau dua qhov porosity ntawm cov roj thiab roj reservoir, qhov kev nyeem ntawv ntawm epithermal n txoj kev qis dua. Cov ntaub ntawv tau txais thaum lub sij hawm neutron-neutron logging, tso cai rau koj los xam cov porosity yam. Vim qhov txo qis rhiab heev ntawm epithermal particle txee, txoj kev no muaj qis dua qhov tseeb.

Cov hluav taws xob hluav taws xob hluav taws xob raug tshem tawm los ntawm cov hluav taws xob hluav taws xob rau txoj hauv kev ntev dua li cov epithermal, thiab lawv qhov nruab nrab lub neej yog txiav txim siab los ntawm kev sib piv sib piv nrog rau cov ntsiab lus ntawm chlorine, boron thiab lub ntiaj teb tsis tshua muaj. Chlorine muaj nyob rau hauv cov dej uas muaj salinity siab. Roj thiab roj-cov kabmob pob zeb yog tus cwj pwm los ntawm lub neej ntev ntawm thermal hais. Cov cuab yeej no yog lub hauv paus ntawm lub hauv paus ntsiab lus ntawm neutron-neutron txoj kev ntsuas los ntawm thermal n.

Neutron gamma ray logging

Neutron gamma-ray kev tshawb fawb ntsuas gamma hluav taws xob, uas yog tsim thaum lub sij hawm ntes thermal n. Aquifers yog qhov txawv los ntawm kev nyeem ntau dua, piv nrog cov roj bearing, los ntawm 15-20%(nrog tib porosity). Qhov sib txawv tseem ceeb ntawm cov txheej txheem dhau los yog qhov kev nyeem ntawv ntawm cov cuab yeej no nce nrog kev nce hauv salinity ntawm cov dej drilling.

Txij li kev txiav neutron-gamma tseem sau npe cov xov tooj cua hauv cov pob zeb, kho cov ntsiab lus tau qhia los txhais cov txiaj ntsig. Hauv cov roj thiab roj qhov dej, txoj kev no yog siv rau tib lub hom phiaj raws li cov txheej txheem neutron-neutron - kev sib cais ntawm cov pob zeb raws li cov ntsiab lus hydrogen sib txawv, kev txiav txim siab ntawm porosity coefficient, kev txheeb xyuas cov roj-kua thiab dej-roj sib cuag hauv ib cased. Kuj tseem muaj kev sib xyaw ua ke uas kuaj pom n thiab gamma hluav taws xob, uas txhim kho qhov tseeb ntawm kev ntsuas.

Pulse technology

Pulse logging yog ib hom kev tshawb fawb neutron raws li kev tso tawm ntawm neutrons nyob rau lub sijhawm luv luv (100-200 microseconds). Kuj tseem muaj 2 qhov kev hloov kho ntawm cov thev naus laus zis no:

• registration of thermal n;
• ntsuas ntawm ɣ-quanta ntawm hluav taws xob ntes.

Sau npe rau ib qho ntawm cov kev txwv no rau 2 lub sijhawm qhov tseem ceeb, ib tus tau txais lub neej nruab nrab ntawm thermal neutrons hauv cov pob zeb reservoir. Qhov no tso cai rau koj los txiav txim qhov muaj qee yam tshuaj lom neeg. Aquifers muaj kev nyeem ntawv qis dua rau lub sijhawm ncua sij hawm ntev dua li cov roj thiab roj reservoirs.