How do you interpret porosity logs?
How do you interpret porosity logs?
To obtain porosity, read the value directly from the log. If the log is recorded in limestone units and the formation you wish to evaluate is sandstone or dolomite, then correct the log value by using the appropriate chart in a log interpretation chartbook.
How do you read a well log?
Follow the Ko Ko Rules:
- Tight non-reservoir: Right-Right-Right-Right.
- Shale: Right-Right-Right-Left.
- Low porosity (tight) reservoir: Left-Right-Right-Right.
- Water bearing reservoir: Left-Left-Left-Left.
- Oil bearing reservoir: Left-Right-Left-Left.
- Gas reservoir: Left-Right-Left-Right.
What is Rhob log?
The density log usually labelled ‘RHOB’ measures the density of the borehole and the rocks penetrated by the drill bit. The unit for density is gram per cubic centimetre. The logs (sonic and density) measurements are usually made every 6 in. down hole, but must be aligned to be ‘on-depth’ with each other.
What does spontaneous potential measure?
The spontaneous potential log (SP) measures the natural or spontaneous potential difference (sometimes called self-potential) that exists between the borehole and the surface in the absence of any artificially applied current.
What are the three open logs used to evaluate porosity?
The three open-hole logs used to evaluate porosity are: The sonic log. The density log. The neutron log.
What is well log interpretation?
Well logs present a concise, detailed plot of formation parameters versus depth. From these plots, interpreters can identify lithologies, differentiate between porous and nonporous rock and quickly recognize pay zones in subsurface formations.
What is well log analysis?
Well logging is a study of acquiring information on physical properties of rocks that are exposed during drilling of an oil well. The key purpose of well logging is to obtain petrophysical properties of reservoirs such as Porosity, Permeability, hydrocarbon saturation etc., for hydrocarbon exploration.
What does a neutron log measure?
The neutron log is sensitive mainly to the amount of hydrogen atoms in a formation. Its main use is in the determination of the porosity of a formation. The tool operates by bombarding the formation with high energy neutrons.
How does density log work?
Density logging tools. A density-logging tool sends gamma rays into a formation and detects those that are scattered back. Typical logging sondes use a Cesium-137 source, which emits gamma rays of 0.66MeV. At this high energy level, Compton scattering dominates.
What is water saturation?
1. n. [Formation Evaluation] The fraction of water in a given pore space. It is expressed in volume/volume, percent or saturation units. Unless otherwise stated, water saturation is the fraction of formation water in the undisturbed zone.