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