Spontaneous potential log, commonly called the self potential log or SP log, is a passive measurement taken by oil industry well loggers to characterise rock formation properties. The log works by measuring small electric potentials (measured in millivolts) between depths with in the borehole and a grounded electrode at the surface.

The spontaneous potential log (SP) measures the natural orspontaneous potential difference (sometimes called self-potential ) that exists between the borehole and the surface in the absence of any artificially applied current.

Jul 28, 2016 · The spontaneous potential (SP) log was developed next and was presented along with resistivity logs. It is a measurement of the voltage difference between a movable electrode in the wellbore and a fixed electrode at the surface.

Jan 18, 2022 · The shape of a gamma ray (or SP) log through a sand body is often thought of as a grain size profile. Three basic log shapes are recognized: funnel (coarsening upward), cylinder (blocky), and bell (fining upward) ( Figure 1 ).

Jan 18, 2022 · The volume of shale (V sh) is best estimated by logging measurements that respond primarily to shale, in particular, gamma ray and spontaneous potential (SP). The most common methods for estimating shale volumes from gamma ray and SP logs are outlined here.

Spontaneous potentials (SP) are usually caused by charge separation in clay or other minerals, due to presence of semi-permeable interface impeding the diffusion of ions through the pore space of rocks, or by natural flow of a conducting fluid through the rocks.

Sep 7, 2018 · In SP log curve, two extremes of readings are identified: shale line (or shale baseline) and sand line (Static Spontaneous Potential). Shale line is the reading against the homogeneous shale formation. Shale bed can be usually identified from Gamma Ray log which has very high values.

Mar 15, 2021 · SP Log. The best procedure with dealing with the SP log is to rescale it in units of percent deflection, where a 0% deflection represents the maximum right hand deflection (maximum shale) and a 100% deflection represents the maximum left hand deflection (clean sand). The first step is to establish a shale base line for each SP log.

Spontaneous potential (SP) logs This log measures the electrical current that occurs naturally in boreholes as a result of salinity differences between the formation water and the borehole mud filtrate ( formation and surface).

Jan 22, 2025 · Self-potential (SP) borehole logging is an electrical wireline method that passively measures naturally occurring voltage anomalies along the length of an open, fluid-filled borehole.