Changes

====Sandstone====

====Sandstone====

The potential differences around a sand/shale contact deflect the SP from the shale baseline. The deflection is negative for a normal salinity contrast (borehole fresher than formation). Little change occurs within a sand interval, so a clean sand shows a straight-line “sand line” ([[:file:quick-look-lithology-from-logs_fig1.png|Figure 1c]]). (For more details on SP shale and sand baselines, see [[Determination of water resistivity]].)

The potential differences around a sand-shale contact deflect the SP from the shale baseline. The deflection is negative for a normal salinity contrast (borehole fresher than formation). Little change occurs within a sand interval, so a clean sand shows a straight-line “sand line” ([[:file:quick-look-lithology-from-logs_fig1.png|Figure 1c]]). (For more details on SP shale and sand baselines, see [[Determination of water resistivity]].)

====Tight rocks====

====Tight rocks====