Diagrafia geofizica & seismica stratigrafica

De ce se sapa sonde ?Dificil din punct de vedere tehnic, costuri foarte mari, afecteaza mediul inconjurator si in cele mai multe cazuri sondele sunt fara un rezultat multumitor

Necesitatea din ce in ce mai mare pentru energie Identificarea rocilor rezervoare pline cu hidrocarburi descoperirea zacamintelor de hdrocarburiPrima sonda este cu rezultat multumitor. Unde o sapam pe a doua?

Sa consideram ca avem informtii din patru sonde

Gandirea unui geolog foarte conservator

Gandirea unui geolog conservator

Gandirea unui geolog optimist

Gandirea unui geolog foarte optimist

Gandirea unui geolog extraordinar de optimist

Gandirea unui geofizician

Gandirea unui inginer de zacamant

Ce spune un geoscientist educat?

Date si informatii rezultate in urma saparii sondelor

datele din sonda sunt directe, corecte .dar foarte foarte scumpe (cele mai scumpe informatii sunt din crote mecanice) sunt necesare metode mai eficiente Geofizica Balanta dintre costuri, calitatea si exactitatea datelor. La scara mare dar cu o rezolutie scazuta: gravimetrie si magnetometrie La scara mica dar cu o rezolutie buna: seismica 2D si 3D si bineinteles diagrafia geofizica

Metodele geofizice

Diagrafia geofizica Masoara proprietatile petrofizice ale rocilor, indicator al litologiei, predictia sistemului depozitional Singurele observatii directe Carote Masoara propagarea undelor elastice, predictia geometriei dar si a litologiei Seismica Masoara campurile fizile ale Pamantului la asacar mare, predictia structurii pamantului Gravimetrie si magnetometrie

Diagrafia geofizica & SeismicaDiagrafia geofizica Rezolutie verticala buna (metrii) Identifica limitele secventiale Identificarea litologiei sedimetelor investigate Seismica Identifica geometria interioara a secventelor Caracterizarea continuitati laterale Rezolutie vericala limitata (zeci de metrii))

Analiza faciesului secventelor se poate face folosind in principal: Diagrafia geofizica si carotele

Seismica

Diagrafia geofizica ( corelarea curbelor geofizice)

Identificarea limitelor secventiale, delimitarea limitelor sedimetare si identificarea faciesului sedimentologic

Ajuta la identificarea sistemelor depozitionale si litologice pe liniile seismice

Resistivitatea Potentialul Spontan (SP) Gamma Ray (Radioactiv) Neutronic Densitatea Acustic de viteza

Well Log CodeAUD BHV BIL BPP BT CAL CBL

Code DefinitionNoise Log, Audio, Experimental Noise Log Velocity Borehole Image Log Borehole Profile Plot Borehole televiewer Caliper Cement Bond, Cement Curve, Cement Quality Casing collar locator Cased hole neutron Casing inspection log Computer Process, Cyberlook, Complex lithology, Hydrocarbon Identification, Laserlog Computer Processed (TVD) Density, Spectral density, Slim hole density Depth Correlation Log Deviation survey, Borehole directional survey Dual laterlog Dip Meter, Continuous dipmeter, High resolution dipmeter Density,Neutron Density, Neutron, Micro(Mini)Log Density, Neutron, Micro(Mini)log (TVD) Density (TVD) Electric Log Electromagnetic propagation Fracture Identification Log Formation Micro Scanner Formation Test, Repeat formation tester Gamma Ray, Radioactivity Gamma Ray (TVD) Induction Resistivity Induction, Density, Neutron Induction, Density, Neutron, Microlog/Minilog Induction, Den, Neu, Micro (Mini) log TVD Induction, Den, Neutron, Sonic Induction, Density, Neutron, Sonic, Micro(Mini)og Induction, Den, Neutron, Sonic(TVD) Induction, Density, Neutron (TVD) Induction, Density (TVD)

Multe alte tipuri de diagrafie geofizica

CCL CHL CIL CP CPTVD D DC DIR DLL DM DN DNM DNMTVD DTVD EL EMT FIL FMS FT GR GRTVD I IDN IDNM IDNMTVD IDNS IDNSM IDNSTVD IDNTVD IDTVD

ResistivitateaCea mai cunoscuta si utilizata diagrafie geofizica Masoara rezistenta la curgerea curentului electric Depinde de porozitatea si flidul din porii rocii Se poate folosii si la identificarea litologiei

Shallow potentiala raza de investigare 0.4 m si 1,6 m

Deep gradienta raza de investigare 5,6 m

Potential Spontan (SP)

Masoara curentul electric din sonde (diferenta in potentialul electric dintre formatiune si suprafata) Depinde de diferenta de salinitate a apelor de zacamant si a noroiului de foraj Estee un indicator al permeabilitatii (raportul argila/gresie in rocile siliciclastice) Separa limitele dintre stratele poros-permebile ale gresiilor si stratele argiloase impermeabile.

Linia argilei

Linia gresiei

calitativfoarte sensilil la salinitatea noroiului de foraj Inainte de utilizare trebuie calibrat

Gamma Ray

Masoara radioactivitatea formatiunilor Argilele arata cele mai mari valori ale radioactivitatii datorita continutului foarte mare de elemente radoactiv Gamma ray arata informatii despre granulometria (si dec indirect despre sistemul depozitional) Gamma ray este cea mai utilizata diagrafie geofizica folosita in stratigrafie secventiala

Functioneaza si pentru SP

After Harris & Saller 1999

NeutronicMasoara porozitatea aparenta a formatiunilor prin masurarea continutului de hidrogen Folosit cu densilogul poate identifica litologia:1.2. 3.

Calcare curate: neutronic si densilogul (valori mari) Gresii curate diferenta mica, densilogul este deplasat spre dreapta Cresterea continutului de argila : reducere a valorilor pe neutronic datorita continutului mare de apa (legata si de cristalizare), densitate mica densilogul ramane in dreapta neutronicului)

DensilogMasoara densitatea formatiunilor Folosit ca o masura a porozitatii Ajuta la diferentierea litologiilor atunci cand este asociat cu Neutronicul Folosit impreuna cu acusticul de viteza ajura la generarea traselor seismice sintetice pentru a face legatura intre datele din sonde si seismica

Acusticul de vitezaMasoara viteza sunetului in formatiune Variaza cu porozitatea si litologia Folosit cu Densilogul si Neitronicul se genereaza seismograma sintetica folosita in calibrarea datelor din sonda cu datele seismice

Sonda & Seismica

Sonde & Seismica

Electrofaciesuri

Secventele sedimetare & diagrafia geofizica LST - Basin Floor FanGresii masive caracterizate de un electrofacies cilindru.Basin Floor Fan

Deasupra si dedesubt, de obicei, se gasesc argile

Limita superioaraArgile pelagice se suprapun peste stratul de gresii si formeaza un excelent strat protector

SB

SP or GR Pelagic Highstand Basin Floor Fan Slope Fan Systems Tract

Gresii ale turbiditelor de panta (nu constituie strat protector) La limita superioara a BFF exista de obicei o zona de tranzitie intre BFF si Slope Fan, uneori pot apare erozoiuni post depozitionale datorita curentilor submarini

Condensed Section

INTERVALUL Basin Floor FanIn general gresii masive, pot apare intercalatii subtiri si rare argiloase Amalgamated turbidite sands, winnowed sands or contourites Stratele argiloase pot constitui bariere pentru migrarea hidrocarburilor pe verticala Satorita prezentei intervalelor argiloase exista posiblitatea ca fiecare interval grezos sa aiba limita propie de contact dintre hisdrocarburi si apa

Limita inferioara (Limita secventiala)Gresiile BFF stau pe argile pelagice sau marne Limite erozionale sunt frecvente

Secventele sedimetare & diagrafia geofizicaLST - Slope Fan SystemCumul de canale caracterizate de un electrofacies zimtat (bow or eggs shaped logs)Slope Fan System

SP or GR

UPPER BOUNDARYNervous log response signifies a shift from overlying pelagic shale to laminated sand-shale response of the slope fan. Fining upward digitated log character below boundary. Maximum clay-shale above boundary. Overlying shale typically has a faunal abundance peak

PGC

INTERVALChannel-overbank units show a crescent shaped log character. Channel fill facies may be massive turbidite sands, that sine up with sharp bases or fine-grained turbidites Within leveed channel unit overbank sands thicken, then tin and become sparse upward Lower part of unit consists of attached lobe sands that thicken and become more abundant upwardsMulti-storey sands channel fill

Lowstand Systems Tract

Slope Fan Complex

Channel/ overbank unit 2

LCC

Channel/ overbank unit 1

Minor faunal abundance peaks between leveed channel units 8 to 10 channel overbank units may stack on one lowstand systems tract

BFF

LCC

LOWER BOUNDARYLies on sequence boundary or on a basin floor fan. Channelised surfaces common at base. Hemipelagic shales with faunal abundance peaks may separate units and may seal basin floor fan. Boundary commonly conformable in basin and erosional on slope.

Secventele sedimetare & diagrafia geofizica LST - Prograding ComplexCoarsening upward signature with thick blocky sands near top, typically fluvial or deltaic in origin.

TS

Lowstand Delta

SP or GR HST TST

UPPER BOUNDARYTransition from upward shallowing to upward deepening Toplap below boundary Transgressive surface of erosion on shelf

INTERVALThick intervals of blocky sands common near top Fluvial and deltaic sands typical

Lowstand Systems Tract

LCC

Prograding Complex pinches out against break in slope at shelf edge

Slope Fan Complex

LOWER BOUNDARYMaximum clay-shale point Minor faunal abundance peak

Secventele sedimetare & diagrafia geofizica Transgressive Systems TractFining and thinning upward log signature (backstepping parasequences). Neritic shales on top with beach, shoreface sands or non-marine sediments with possible coals at base.MF

Transgressive

MAXIMUM FLOODING SURFACE

SP or GRHST

Lowest resistivity and highest GR values indicate the most clay-rich shale A planktonic faunal abundance peak is common at boundary Discontinuity surface: downlap above apparent truncation below

SB

INTERVALBecomes finer grained and thinner bedded upwardNeritic shales form the best seal near the top

Transgressive Systems Tract

Estuarine, beach and shoreface sands occur near base Basinal equivalent is pelagic shale Correlation is good but backstepping parasequences are time transgressive Barrier island and shoreface sands can be well preserved, better sorted and more permeable than HST sands

HST or PGC

SEQUENCE BOUNDARYOnlaps sequence boundary Lowstand incised valley erosion common Erosional truncation common below boundary

Secventele sedimetare & diagrafia geofizica Highstand Systems TractCoarsening upward log signature. Typically fluvial or deltaic with non-marine sediments at the top. May be indurated with soil profiles on upper surface.SB

Highstand

SP or GR LST

SEQUENCE BOUNDARYOnlap above boundary Fluvial (meandering streams, alluvial fans) below boundary Lowstand erosion and incised valleys common Submarine canyons cut into shelf of preceding highstand systems tract Truncation and toplap common below boundary

MF

INTERVALShoreline, fluvial and deltaic sands predominate near the topBecomes coarser grained and thicker bedded upward Progrades toward basin into neritic shales

HST

Basinal equivalent is pelagic shale Correlation of sands is difficult due to discontinuous coastal plain and alluvial faices Consequently reservoir continuity is only fair to poor

MAXIMUM FLOODING SURFACECommonly lowest resistivity highest gamma Downlap of shale-rich clinoform toes onto boundary Planktonic abundance peak (may be a thin limestone)

TST

Secventele sedimetare & diagrafia geofizica

Secventele sedimetare & diagrafia geofizicaIdentificarea limitelor secventiale pe diagrafia geofizica Limitele secventiale In practica identificarea limitelor secventiale pe diagrafie este foarte complicata, sunt necesare si informatiii din carote (sedimetologice, petrografice, bioastratigrafice) Eroziunile din zona selfului pot fi recunoscute prin absenta stratelor care pot fi observate doar folosind datele biostratigrafice Eroziunile din bazin pot fi recunoscute cand turbiditele stau direct pe limita secvential inferioara rezultand pe GR o in scriere caracteristica

Identificarea limitelor secventiale doar pe diagrafie.

Secventele sedimetare & diagrafia geofizicaMaximum flooding surface (Suprafara de inundare maxima) MFS (Suprafara de inundare maxima) se identifica in zona de shelf usor pentru ca separa o unitate retrogradationala TST de una progradationala HST valori mari pe GR In zona pantei continental bazin MSF delimiteaza limitei superioare a unitatea condensata a TST. GR pentru unitatea condensata arata valori ridicate datorita cresterii continutului de argila

Este o auprafata de Downlap Baza clinoformelor (baza HST)

Secventele sedimetare & diagrafia geofizica

MFS in sonde In zona proximala MFS se regaseste intr-o zona agradationala (foarte fificil de identificat pe diagrafie). In zona distala MFS este usor de identificat (progradational peste retrogradational)

Secventele sedimetare & diagrafia geofizica

Sequences on Wireline Logs

System Tracts & Diagrafia Geofizica

Gamma Ray

Neutron-Density

1.

2. 3. 4. 5. 6.

Marcati pe diagrafie tendintele de progradare, adradare, retrogradare (sageti si triunghiuri) Marcati limitele secventiale Marcati Maximum Flooding Surface Ce System Tracts regasiti? Cate parasecvente sunt in HST? Cate parasecvente sunt in Transgressive Systems Tract

DEPOSITIONAL ENVIRONMENT NEARSHORE MARINE

Gamma Ray

Neutron-Density

OFFSHORE MARINE

ESTUARINEFLUVIAL

OFFSHORE MARINE

DEPOSITIONAL ENVIRONMENT NEARSHORE MARINE

Gamma Ray

Neutron-Density

OFFSHORE MARINE

ESTUARINEFLUVIAL

OFFSHORE MARINE

DEPOSITIONAL ENVIRONMENT NEARSHORE MARINE

Gamma Ray

Neutron-Density

OFFSHORE MARINE

MAXIMUM FLOODING SURFACE

ESTUARINEFLUVIAL

SEQUENCE BOUNDARYOFFSHORE MARINE

Usor de recunoscut?....dar nu intotdeauna corectDEPOSITIONAL ENVIRONMENT NEARSHORE MARINE Gamma Ray Neutron-Density

4220m TVDSS3 Parasecvente progradationale

Highstand

OFFSHORE MARINE

4 Parasecvente retrogradationale

TransgresivESTUARINEFLUVIAL

Scara verticala

OFFSHORE MARINE

Highstand4230m TVDSS Date din carote + diagrafie Sedimentologie

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

SGR 20 140

DTCOMP 160

40

HST

SGR 20 140

DTCOMP 160

40

LST HST

SGR 20 140

DTCOMP 160

40

TST LST HST

SGR 20 140

DTCOMP 160

40

HST TST LST HST

SGR 20 140

DTCOMP 160

40

TST HST TST LST HST

SGR 20 140

DTCOMP 160

40

HST TST HST TST LST HST

SGR 20 140

DTCOMP 160

40

LST HST TST HST TST LST HST

SGR 20 140

DTCOMP 160

40

TST LST HST TST HST TST LST HST

SGR 20 140

DTCOMP 160

40

LST TST LST HST TST HST TST LST HST

SGR 20 140

DTCOMP 160

40

TST LST TST LSTHST TST HST TST LST HST

SGR 20 140

DTCOMP 160

40

HST TST LST TST LST HST TST HST TST LST HST

SGR 20 140

DTCOMP 160

40

TST HST TST LST TST LST HST TST HST TST LST HST

SGR 20 140

DTCOMP 160

40

HST TST HST TST LST TST LST HST TST HST TST LST HST

SGR 20 140

DTCOMP 160

40

TST HST TST HST TST LST TST LST HST TST HST TST LST HST

SGR 20 140

DTCOMP 160

40

HST TST HST TST HST TST LST TST LST HST TST HST TST LST HST

SGR 20 140

DTCOMP 160

40

TST HST TST HST TST HST TST LST TST LST HST TST HST TST LST HST

SGR 20 140

HighstandSGR 20 140

Lowstand Progradational Lowstand SF+BFF

Transgresiv