Lecture items Electric Properties of Rocks Factors affecting

Lecture items - Electric Properties of Rocks. - Factors affecting resistivity of reservoirs Electrical Logs (Self Potential log, Conventional resistivity logs , Laterologs, Dual Laterologs, Microspherically focused logs, Induction logs). -

Factors affecting resistivity of reservoirs l Salinity ∞ 1/R l Temperature ∞ 1/R l Saturation ∞ 1/R l Presence of hydrocarbons ∞ R l Lithology plays an indirect role for controlling resistivity

Electrical Logs - Self Potential log, - Conventional resistivity logs , - Focused resistivity Logs, - Microspherically focused logs, - Induction logs.

Self (Spontaneous) Potential (SP) log Objectives l To understand the physical principles behind the operation of spontaneous potential (SP) logging. l To learn how to interpret SP logs in terms of lithology and petrophysical properties. l To understand what corrections needed to be applied to SP log before using it for interpretation.

* Definition. * Units& Presentation. * Applications. * Theory of measurement. -Shale-base line& Sand line -SSP, PSP and SP log readings * Factors affecting on log readings.

SP log “Definition” l The SP is a measure and record of direct current (DC) voltage differences between the naturally occurring potential of a moveable electrode in the well bore, and the potential of a fixed electrode located at the surface. l The SP log is recorded on the left hand track of the log in track #1 l It is measured in millivolts (mv).

SP log “General Uses” l The SP log is used to identify impermeable zones such as shale, and permeable zones such as sand, l Detect boundaries of permeable beds, l Determination formation water resistivity(Rw), l Calculation the volume of shale in permeable beds.

Theory of Measurement