What is laterolog resistivity?
What is laterolog resistivity?
Laterolog resistivity tool injects electric currents into geological formations and records the potential drop across a specific length along the open hole well. Laterolog measurements are related to the electrical resistivity of the formation. Laterolog tools are reliable in boreholes drilled with water-based muds.
What is Groningen effect?
The Groningen effect was named after the large Dutch gas field where the anomaly was first identified. The effect is an anomalously high resistivity reading that occurs for approximately 100 ft [30 m] below a thick, highly resistive bed such as the thick evaporitic Zechstein caprock at the Groningen field.
What is electro logging?
Electric logging consists of lowering a device used to measure the electric resistance of the rock layers in the downhole portion of the well. This is achieved by running an electric current through the rock formation and measuring the electrical resistance that the current encounters along its way.
What does spontaneous potential measure?
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 change in voltage through the well bore is caused by a buildup of charge on the well bore walls.
What is deep resistivity?
The annulus zone is logged as medium depth resistivity. The uninvaded zone is the furthest zone from the borehole and has not had any drilling fluid enter it. The resistivity in the uninvaded zone is the true resistivity of the original fluid and formation. The uninvaded zone is logged as deep resistivity.
What is meant by resistivity?
Resistivity, electrical resistance of a conductor of unit cross-sectional area and unit length. A characteristic property of each material, resistivity is useful in comparing various materials on the basis of their ability to conduct electric currents. High resistivity designates poor conductors.
What is LLD log?
In well log, LLD (laterolog deep) and LLS(laterolog Shallow) readings have a huge difference in value against coal zone, what does it indicate? 1. In rest of the log, LLD and LLS values are nearly same. Because of coal zone, the correlation coefficient between LLD and LLS is coming to 0.54.
What is Dual Laterolog?
The Dual Laterolog (DLL) provides two resistivity measurements with different depths of investigation: deep (LLD) and shallow (LLS). For the deep measurement, both measure and focusing currents return to a remote electrode on the surface at large distance.
What are the types of well logs?
Well Log Techniques
- Acoustic Logs. Cement Bond Log. Cross-Dipole Acoustic Log.
- Caliper Log.
- Chemical Logging.
- Density Log.
- Gamma Log.
- Image Logs.
- Mud Logging.
- Neutron Log.
How do you measure self potential?
The self-potential (SP) technique is a passive electrical geophysical method based upon the measurement of spontaneous or natural electrical potential developed in the earth due to: 1) electrochemical interactions between minerals and subsurface fluids; 2) electrokinetic processes resulting from the flow of ionic …
What type of log Do we use for porosity calculation?
The combination of the density and neutron logs provides a good source of porosity data, especially in formations of complex lithology. Better estimates of porosity are possible with the combination than using either tool or sonic separately because inferences about lithology and fluid content can be made.
What are the advantages of the Laterolog method?
In this method a current, preferably of constant intensity, is forced into the formation perpendicularlyto the wall of the hole as a sheet of predetermined thickness by means of aspecial electrode arrangement and of an automatic control system. The essential advantages of the Laterolog over the regular resistivity logsare explained.
What is the schematic diagram of Laterolog 7?
Schematic diagrams of laterolog 7 (left), laterolog 3 or Guard log (middle) and spherically focused log (right). Grey shading represents desired current path. The Laterolog 7 electrode arrangements can be likened to two ES logs spliced together, with one tool upside down.
Why was the Laterolog 8 replaced by the dual induction log?
The Laterolog 8, with 8 electrodes, was designed to replace the 16 inch normal on the induction log when it was re-introduced as the dual induction log. It had better bed resolution and less borehole effect, and survived in saltier muds than its predecessor.
Is the Laterolog a DC or direct current tool?
The laterolog is a direct current (DC) tool based on Ohm’s Law. The tools have been designed to produce reliable resistivity measurements in boreholes containing highly saline drilling fluids and/or when surrounded by highly resistive rocks.