- Industry: Oil & gas
- Number of terms: 8814
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A fluid prepared to counteract the corrosive effect of acids or acidic treatment fluids. Neutralizing solutions generally are used when the components to be protected cannot be adequately flushed or when there is a risk that residual fluids may cause problems through prolonged exposure. Neutralizing solutions are commonly formulated with soda ash to provide an inexpensive, nondamaging alkaline fluid that does not create excessive disposal difficulties.
Industry:Oil & gas
A gamma ray interaction in which the gamma ray is fully absorbed by a bound electron. If the energy transferred exceeds the binding energy to the atom, the electron will be ejected. Normally, the ejected electron will be replaced within the material and a characteristic X-ray will be emitted with an energy that is dependent on the atomic number of the material. The highest probability for this effect occurs at low gamma ray energy and in a material of high atomic number. The photoelectric effect is the principle behind the PEF log, which identifies lithology.
Industry:Oil & gas
A gamma ray interaction in which the gamma ray collides with an electron, transferring part of its energy to the electron, while itself being scattered at a reduced energy. Compton scattering occurs with high probability at intermediate gamma ray energies, between 75 keV and 10 MeV in sedimentary formations. When a beam of gamma rays traverses a material, the total reduction due to Compton scattering depends on the electron density of the material the higher the density, the larger the reduction. This is the basis for the density log. Compton scattering is also an important mechanism in gamma ray detectors.
Industry:Oil & gas
A formation with directionally dependent properties. The most common directionally dependent properties are permeability and stress. Most formations have vertical to horizontal permeability anisotropy with vertical permeability being much less (often an order of magnitude less) than horizontal permeability. Bedding plane permeability anisotropy is common in the presence of natural fractures. Stress anisotropy is frequently greatest between overburden stress and horizontal stress in the bedding plane. Bedding plane stress contrasts are common in tectonically active regions. Permeability anisotropy can sometimes be related to stress anisotropy.
Industry:Oil & gas
A formation where the velocity of the compressional wave traveling through the borehole fluid is less than the velocity of the shear wave through the surrounding formation. In such conditions a shear head wave is generated, so that standard techniques based on monopole transducers can be used to measure formation shear velocity. <br><br>In hard formations, several normal modes are excited in addition to the Stoneley and leaky modes.
Industry:Oil & gas
A formation layer above or below the layer being measured by a logging tool. The term is used in particular to describe the adjacent layers above or below a horizontal well. In a vertical well, the term shoulder bed is more common. The term adjacent bed is used in both cases.
Industry:Oil & gas
A formation layer above or below the layer being measured by a logging tool. The term is used in particular in resistivity logging to describe the layers above and below a reservoir. Some resistivity tools, such as induction and laterolog devices, can sense beds located tens of feet from the measure point and can be significantly affected by shoulder beds even when the reservoir is thick. The term is more commonly used for vertical wells, and is derived from the typical picture of resistivity log response across a reservoir: a high resistivity reservoir (the head) with two low-resistivity shales above and below (the shoulders). The term also may be used in horizontal wells, although in that context the term surrounding bed is more common. The term adjacent bed is used in both cases.
Industry:Oil & gas
A formation interval that has become overpressured by the injection of drilling or treatment fluids.
Industry:Oil & gas
A formation in which the velocity of the compressional wave traveling through the borehole fluid is greater than the velocity of the shear wave through the surrounding formation. In such conditions, there is no critical refraction of the shear wave and no shear head wave generated, so that standard techniques based on monopole transducers cannot be used to measure formation shear velocity. Instead, it is necessary to use dipole sources to excite the flexural mode. The velocity of the latter is closely related to that of the shear wave. In very slow formations, such as in high-porosity gas sands, the formation compressional velocity also may be less than the borehole fluid velocity, causing no compressional head wave. In such cases, it is possible to estimate the formation compressional velocity from the low-frequency end of a leaky mode.
Industry:Oil & gas
A form of kriging that involves multiple variables. For example, well data may be used to generate one semivariogram, and three-dimensional seismic data used to generate another. Both semivariograms, along with a cross-variogram model, can then be used to generate a cokriged map.
Industry:Oil & gas
