Which log uses a gamma ray source?

The Gamma log is used to record the naturally occurring radiation found in the surrounding borehole rocks from three primary isotopes: Potassium-40 (K), Thorium (Th), and Uranium (U) . Clays have the highest concentration of these radioactive isotopes; hence the Gamma log is also known as the clay log, or shale log.

Which of the following from gamma ray log is best indicator of clay content of rock?

Spectral gamma ray logs are most useful in identifying the following: Clay minerals. Illite clays are rich in potassium, whereas smectite and kaolinite contain thorium. The thorium to potassium ratio can distinguish illitic from smectitic shales and so provide a correlation tool.

What is radioactive logging?

i. A log of a borehole obtained through the use of gamma, neutron, or other radioactivity logging methods. ii. The generic name for well logs whose curves derive from reactions of atomic nuclei involving the behavior of gamma rays and/or neutrons.

What is spectral gamma ray logging?

The spectral gamma ray log measures the natural gamma radiation emanating from a formation split into contributions from each of the major radio-isotopic sources. Analysis of the sources of the natural gamma radiation give us added information concerning the composition and likely lithology of the formation.

What does sonic log measure?

The sonic or acoustic log measures the travel time of an elastic wave through the formation. This information can also be used to derive the velocity of elastic waves through the formation. Its main use is to provide information to support and calibrate seismic data and to derive the porosity of a formation.

What is gamma ray log and its purpose?

Gamma ray logging is a method of measuring naturally occurring gamma radiation to characterize the rock or sediment in a borehole or drill hole. It is a wireline logging method used in mining, mineral exploration, water-well drilling, for formation evaluation in oil and gas well drilling and for other related purposes.

Why is gamma ray log used as a shale indicator?

Identifying shale volumes. The most common use of gamma ray logs is to estimate the shale “volume” in rocks. It is important to remember that the tool measures radioactivity, and the correlation to shale content is empirical. Shales are presumed to be composed of clay minerals.

What is gamma in directional drilling?

In addition to formation correlation capability, the focusing characteristic of the gamma detector allows detection of approaching bed boundaries in near horizontal wells while drilling, allowing controlled drilling between bed boundaries.

What is well logging and its purpose?

Well logging allows a detailed record of the geologic formations penetrated by a borehole. The log is based on physical measurements made by geophysical tools lowered into the hole. Historically, the first logging measurements consisted of basic electrical logs (resistivity) and spontaneous potential (SP) logs.

What is GR in oil and gas?

1. n. [Formation Evaluation] An abbreviation for gamma ray, usually with reference to the gamma ray log. See: carbonate gamma ray, gamma ray log, natural gamma ray spectroscopy, potassium, thorium, uranium. © 2022 Schlumberger Limited.