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IntroductionWell loggingTypes of Well Logging Electrical LoggingTypes of Electrical Logging Spontaneous Potential Logging Resistivity Logging Induction LoggingConclusion References
IntroductIon
•Geophysical exploration-study of physical properties Geological materials by using appropriate instruments•Types of geophysical exploration: •Electrical•Magnetic•Gravity•Seismic•Radioactive and •Well logging
Well loggIng
Continuous recording of a physical parameter of the
formation with depth by introducing sondeFirst developed by Schlumberger brothers in 1927To identify the productive zone of hydrocarbon and
its mobilityTo define petrophysical parametersTo determine depth, thickness, formation
temperature and pressure of reservoirTo distinguish between oil, gas and water zones in a
reservoir
Types of well logging
Electrical method Radioactivity methodSonic loggingMiscellaneous logging
electrIc loggIng
Continuous record of the electrical properties of the fluids and geologic materials Performed by measuring current through electrodes in the logging device or sondeUsed in geological investigations to assess the variation with depth of geologic materials and associated fluidsCorrelate and determine the continuity of geologic strata Types- Resistivity, Spontaneous(Self) Potential, Induction logging
Spontaneous Potential LoggingDue to salinity between formation water and mud filtrate against permeable bedsThe measurement is made through a potential meterUseful in Establishing correlation of beds from well to wellTo determine bed boundaries and thicknessTo evaluate the formation water resistivity To delineate porous and permeable reservoir rock
Resistivity Logging
oAbility to impede the flow of electric current oFall in the range from 0.2 to 100 ohm metero4 electrodes are usedoCarried out by lowering of electrodesoTypes
Normal and Lateral logs
Laterolog
Microlog
Microlaterolog
Proximity
Normal and Lateral log4 electrodes-2 potential(M and N), 2 power
electrodes(A and B)
Normal device- A and M are closely spaced ,
B is grounded and N is far away from A-M
Lateral device- M and N closely spaced with
electrode A
Microlog
The resistivity of a small volume of formation
3 electrodes(A, M1 and M2) in vertical line
Spacing is 1 inch( 2.5cm)
Excellent permeability indicator
MicrolaterologCentral electrode very small size and 3 circular
electreodes concentric with 1-2 cm
Accurate estimate of flushed zone resistivity and
hence porosity
Proximity logUsed with other resistivity logs
Evaluate permeable zones exhibiting thick (up to
2 cm) mud cakes
Induction LoggingIn dry boreholes or boreholes containing
nonconducting fluids
Based electromagnetic induction
Parameter is conductivity
Transmitter coil and receiver coil coaxially
supported by an insulating mandrel
Laterolog
4 electrodes- one at centre and 3 are
symmetrically placed with centre one
Case study 1:
Case study 2:
Case study 3:
Well logging technique is one of the type used in
geophysical explorationThis can be performed by logging devices or SONDEElectrical logging can be done by measuring current
through electrodes in the logging deviceSpontaneous potential, resistivity and induction loggingTo identify productive zone of hydrocarbon, to define
petrophysical parameter, to determine depth,
formation temperature and pressure of a reservoir, to
measure hydrocarbon mobility
Conclusion
References M.G. Ramachandra Rao,
Outlines of Geophysical prospecting (1975)
Prasaranga Manasagangotri Mysore pp:343-3661981,Milton B Dobrin, Introduction to
geophysical prospecting , Third edition,
Mcgraw- HILL Book Company pp:568-622www.wikipedia.comwww.greatgeophysics.com/logginginfo.html www.geologging.com/english/products/.../ele tric_log.htm