Gamma-rays

A hole section which has been cored will subsequently be logged using wireline tools (see later in this section). A gamma ray (GR) measurement will be taken from the core itself, thus allowing calibration of wireline logs with core data. 

Figure 5.37 depicts the basic set up of a wireline logging operation. A sonde is lowered downhole after the drill string has been removed. The sonde is connected via an insulated and reinforced electrical cable to a winch unit at the surface. At a speed of about 600m per hour the cable Is spooled upward and the sonde continuously records formation properties like natural gamma ray radiation, formation resistivity or formation density. The measured data is sent through the cable and is recorded and processed in a sophisticated logging unita the surface. Offshore, this unit will be located in a cabin, while on land it is truck mounted. In either situation data can be transmitted in real time via satellite to company headquarters if required. 

Azimuthal resistivity (depth of investigation Gamma ray 12in. orless) detector... 

If a sand line (0% shale) and a shale line (100% shale) are defined on the gamma ray log, a cut-off limit of 50% shale can be used to differentiate the reservoir from non-reservoir intervals. This type of cut-off is often used in preliminary log evaluations and is based on the assumption that reservoir permeability is destroyed once a rock contains more than 50% shale. 

In stacked reservoirs, such as those found in deltaic series, it is common to find that some zones are not drained effectively. Through-casing logs such as thermal neutron and gamma ray spectroscopy devices can be run to investigate whether any layers with original oil saturations remain. Such zones can be perforated to increase oil production at the expense of wetter wells. 

The principles of gamma-ray radiography are the same as X-ray radiography except that a radioisotope is used as the radiation source rather than an X-ray tube. 

Specimens used in tests were sections of cables with PVC outer coating. PVC was plasticized with DOF softener. The materials considered were exposed to the radiation and thermal aging. The samples have been irradiated at room temperature by hard gamma rays with 10 rad/sec dose power. A number of samples had been heated for long different times at 90°C. Besides a special specimens were cut out from outer coating for test on tensile machine like "Instron". The total doses of irradiation, times of heating and elongations at break obtained with "Instron" are listed in Table 1. 

We use the X or gamma rays power penetrating to detect possible heterogeneities in inspected pieces. These rays are absorbed by the matter crossed, essentially by the photoelectrical effect, (fig. 02). 

Due to the great number of disruptive factors, the visual information provided by an X or gamma ray image is complex. The processed images are characterised by three particular phenomena ... 

X- and Gamma-Ray Computed Tomography Scanners for Industrial Applications. 

Various computed tomography CT- scanners for industrial applications have been designed and constructed) They use as radiation sources X-ray tubes or gamma emitting radioisotopes and as detectors NaI(Tl)-scintillators for gamma rays and image intensifiers for X-rays. 

In high-energy physics experiments there can be many interfering events superimposed on the events of interest. An example is the detection of gamma rays in the presence of high-energy electrons and protons. The... 

Germanium is very similar to Si, but its band gap is too small for many practical applications. Large crystals of ultra-high-purity Ge have been grown for use as gamma-ray detectors. In such crystals, the net concentration of... 

Natural titanium is reported to become very radioactive after bombardment with deuterons. The emitted radiations are mostly positrons and hard gamma rays. The metal is dimorphic. The hexagonal alpha form changes to the cubic beta form very slowly at about 88O0C. The metal combines with oxygen at red heat, and with chlorine at 550oC. 

Cobalt-60, an artificial isotope, is an important gamma ray source, and is extensively used as a tracer and a radiotherapeutic agent. 

The most important types of radioactive particles are alpha particles, beta particles, gamma rays, and X-rays. An alpha particle, which is symbolized as a, is equivalent to a helium nucleus, fHe. Thus, emission of an alpha particle results in a new isotope whose atomic number and atomic mass number are, respectively, 2 and 4 less than that for the unstable parent isotope. 

Emission of an alpha or beta particle often produces an isotope in an unstable, high-energy state. This excess energy is released as a gamma ray, y, or an X-ray. Gamma ray and X-ray emission may also occur without the release of alpha or beta particles. 

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