MT for Hydrocabon exploration

8/7/2019 MT for Hydrocabon exploration

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Welcome

Mahavir Singh

M.Tech. (AGP)-III

IIT -Roorkee


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MagnetoMagneto--telluric fortelluric for

Hydrocarbon ExplorationHydrocarbon Exploration


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IntroductionIntroduction

The magnetic fields are produced mainly by the interactionThe magnetic fields are produced mainly by the interactionbetween the Solar wind and Magnetosphere or Ionosphere;between the Solar wind and Magnetosphere or Ionosphere;

MTMT measuresmeasures naturallynaturally occurring,occurring, timetime--varyingvarying magneticmagnetic andandelectricelectric fieldsfields thatthat areare foundfound inin thethe earthearth;;

FromFrom thesethese measurementsmeasurements wewe cancan derivederive resistivityresistivity estimatesestimates ofofthethe subsurfacesubsurface ;;

SourceSource ofof MTMT SignalSignal::-- LowLow freqfreq.. signalsignal (11 Hz)Hz) worldworld--widewide thunderstorms,thunderstorms,usuallyusually nearnear thethe equatorequator


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Interaction of solar particles with earths magnetic field

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Field setupField setup


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Some Basic AspectsSome Basic Aspects

NaturalNatural variationsvariations inin thethe earth'searth's magneticmagnetic fieldfield induceinduce electricelectriccurrentscurrents (or(or tellurictelluric currents)currents) underunder thethe earth'searth's surfacesurface;;

TelluricTelluric currentscurrents followfollow inin thethe surfacesurface layerslayers ofof thethe earthearth;;

TheThe ratioratio ofof thethe electricelectric fieldfield toto magneticmagnetic fieldfield (E/H)(E/H) cancan givegivesimplesimple informationinformation aboutabout thethe subsurfacesubsurface conductivityconductivity;;

TheThe ratioratio atat higherhigher frequencyfrequency rangerange givesgives informationinformation onon thetheshallowshallow Earth,Earth,

TheThe ratioratio atat lowlow--frequencyfrequency rangerange givesgives deeperdeeper informationinformation;;


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Subsurface information from MT?Subsurface information from MT?

TheThe mainmain parameterparameter thatthat isis derivedderived fromfrom MTMT isisresistivityresistivity;;

TheThe factorfactor affectingaffecting resistivityresistivity areare Lithology,Lithology, PorePore--fluid,fluid,

Pressure,Pressure, andand TemperatureTemperature;;

TheThe MTMT datadata cancan bebe interpretedinterpreted toto givegive anan estimateestimate ofofresistivityresistivity variationsvariations withwith depthdepth;;

TheThe resistivityresistivity ofof mostmost rocksrocks atat thethe lowlow frequenciesfrequencies isiscontrolledcontrolled byby thethe fluidsfluids containedcontained withinwithin thethe rockrock;;

ResistivityResistivity structurestructure cancan bebe correlatedcorrelated withwith lithologylithologyandand geologicgeologic structuresstructures..


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Apparent resistivity Vs. Frequency, 3Apparent resistivity Vs. Frequency, 3--layer modellayer model


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MT resistivity section in the Columbia PlateauMT resistivity section in the Columbia Plateau



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MT interpretation across an anticlineMT interpretation across an anticline

in the fold belt in Papua New Guineain the fold belt in Papua New Guinea



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MT Applications in Hydrocarbon ExplorationMT Applications in Hydrocarbon Exploration

Before 1980s, MT was used mostly forBefore 1980s, MT was used mostly for

reconnaissance mapping of basins and geothermalreconnaissance mapping of basins and geothermalprospectsprospects

In the 1980s, MT came into use for petroleumIn the 1980s, MT came into use for petroleumexploration, because MT is very portable and itexploration, because MT is very portable and it worksworks

best where seismic has problems;best where seismic has problems;

Subsurface resistivity distribution provide importantSubsurface resistivity distribution provide importantinformation for imaging the reservoirinformation for imaging the reservoir

Resistivity of the common sedimentary rocks dependsResistivity of the common sedimentary rocks dependsmainly on the porosity and salinity of the fluids in rocksmainly on the porosity and salinity of the fluids in rocks

To investigate the distribution of silicate melts in theTo investigate the distribution of silicate melts in theEarth's mantle and crust;Earth's mantle and crust;


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Reservoirs saturated with hydrocarbon are significantlymore resistive than the surrounding sediments;

The resistivity of the surrounding sediments is 1-10 ;m;

The electrical resistivity of basalt, carbonate or salt is inthe range 100-1000;m ;

MT provides information on sub-surface lithology andfluids;

Patterns of resistivity are direct hydrocarbon indicator;

MT methods are capable to detect hydrocarbon at depthmore than 2 km below the mudline from sea floor.

Hydrocarbon DetectorsHydrocarbon Detectors


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Resistivity

values varywith lithology



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TheThe electricalelectrical resistivityresistivity modelmodel fromfrom aa MTMT surveysurvey overoverGeminiGemini prospectprospect inin thethe GulfGulf ofof Mexico,Mexico, laidlaid overover aaseismicseismic sectionsection ofof aa saltsalt intrusionintrusion

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ExampleExample


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MT as a Cost Effective Technique whereMT as a Cost Effective Technique where

seismic has certain problemsseismic has certain problems

WhatWhat makemake seismicseismic difficult,difficult, costly,costly, oror eveneven impossibleimpossible toto useuse..

VolcanicVolcanic rocksrocks nearnear thethe surfacesurface

DenseDense LimestoneLimestone

CrystallineCrystalline basementbasement thrustthrust overover sedimentssediments

RuggedRugged terrainterrain

JungleJungle vegetationvegetation

GeographicGeographic remotenessremoteness

BothBoth naturalnatural--sourcesource methodsmethods (MT)(MT) andand manman--made,made, controlledcontrolled--sourcesource methodsmethods havehave mademade valuablevaluable contributionscontributions inin refiningrefininggeologicgeologic models,models, reducingreducing explorationexploration risk,risk, andand improvingimprovingproductionproduction monitoringmonitoring


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MTMT--StrengthsStrengths

TheThe abilityability toto obtainobtain subsurfacesubsurface informationinformation underunderconditionsconditions wherewhere seismicseismic areare notnot workwork atat allall;;

MTMT measuresmeasures aa differentdifferent physicalphysical property,property, andand thusthuscomplementscomplements otherother geophysicalgeophysical methodsmethods suchsuch asasgravity,gravity, magnetic,magnetic, andand seismicseismic;;

MTMT datadata havehave beenbeen particularlyparticularly helpfulhelpful inin resolvingresolving

ambiguitiesambiguities betweenbetween seismicseismic andand gravity/magneticgravity/magneticinterpretationsinterpretations;;


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Limitations of MTLimitations of MT

MTMT isis aa lowlow resolutionresolution techniquetechnique comparedcompared withwith whatwhat

isis possiblepossible withwith seismicseismic datadata;;

SometimesSometimes somesome geologicgeologic faciesfacies suchsuch asas-- subsub--basalt,basalt, coals,coals,carbonatescarbonates andand freshwaterfreshwater sandssands cancan exhibitexhibit enhancedenhanced electricalelectricalresistivity,resistivity, relativerelative toto itsits surroundingssurroundings

AA resistivityresistivity contrastcontrast isis requiredrequired inin MTMT;;

TwoTwo layerlayer withwith similarsimilar resistivityresistivity isis difficultdifficult toto interpretinterpret inin MTMT;;

GeologicGeologic formationsformations withwith similarsimilar electricalelectrical propertiesproperties areare notnotusuallyusually resolvedresolved fromfrom MTMT;;

MTMT datadata inin thethe presencepresence ofof complexcomplex structure,structure, especiallyespecially ifif thetheeffectseffects ofof twotwo oror moremore structuresstructures areare superimposed,superimposed, maymay bebe veryverydifficultdifficult toto interpretinterpret..


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ConclusionConclusion

MT provide complementary information to conventional seismicexploration methods ;

Strong resistive anomalies in MT Sounding can be used asHydrocarbon Indicators (HI)

The certain resistivity patterns obtained from MT can be used asdirect Hydrocarbon Indicator;

MT can be applied to detecting and characterizing hydrocarbonbearing reservoirs in deep water areas (say 2km below sea floor);


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ThankThankyouyouforforyour kindyour kind

attention!attention!


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ReferencesReferences

ArnoldArnold SS.. Orange,Orange, Member,Member, IEEE,IEEE, ProceedingsProceedings ofof thethe IEEE,IEEE,

VOLVOL.. 7777,, NONO.. 22,, FebruaryFebruary 19891989

KeevaKeeva VozoffVozoff;; GeophysicsGeophysics volvol.. 3737,, NoNo..11,, FebFeb..19721972,, pp9898--141141

wwwwww..searchanddiscoverysearchanddiscovery..netnet

wwwwww..worldoilworldoil..comcom

wwwwww..mtmt..netnet

wwwwww..phoenixphoenix--geophysicsgeophysics..comcom

wwwwww..sciencedirectsciencedirect..comcom

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MT for Hydrocabon exploration