- Industry: Oil & gas
- Number of terms: 8814
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A technique for quantitative mineralogical analysis of a sample of rock by measuring the effect of midrange infrared radiation transmitted through the sample. This radiation excites vibrations in the chemical bonds within the mineral molecules at particular frequencies characteristic of each bond. The transmitted radiation is compared with the spectral standards for a wide variety of minerals to determine the abundance of each mineral in the sample. Typically, a core plug is ground finely and a small (approximately 1 g) representative sample selected and dispersed in a potassium bromide matrix for the measurement.
Industry:Oil & gas
A technique for measuring the pore volume of a core sample from the difference in its weight when dry and when saturated with a liquid. A clean, dry sample is weighed and then evacuated for several hours in a vacuum chamber, flushing with CO<sub>2</sub> to remove remaining air if necessary. A de-aerated liquid is introduced into the chamber and pressured to ensure complete saturation. The saturated sample is then weighed again. The difference in weight divided by the density of the liquid is the connected, or effective, pore volume. <br><br>It is also common to measure the weight of the sample when immersed in the liquid. The grain and bulk volume can then be calculated as in the buoyancy method.
Industry:Oil & gas
A technique for measuring the grain volume of a core sample by observing the change in pressure of helium introduced into a chamber containing the sample. The rock sample is placed in a chamber of known volume. Helium is held in a reference chamber at known volume and pressure, typically 100 to 200 psi (689 to 1379 kPa). The two chambers are connected, causing the helium to drop in pressure as it fills the sample chamber and the pores in the sample. The only volume not filled is the grain volume and the isolated pores. Neglecting the latter, the grain volume can then be calculated from Boyle's Law using the pressure before and after connecting the chambers and the chamber volumes.
Industry:Oil & gas
A technique for measuring the pore volume of a core sample by observing the change in pressure of helium introduced into the pore space. The rock sample is held in a core holder whose internal walls are elastomers, so that the only void space is the internal pore volume. With a suitable holder, the sample can be held under a confining stress. Helium is held in a reference cell at known volume and pressure, typically 100 to 200 psi (689 to 1379 kPa). The helium is introduced to the core sample, dropping in pressure as it fills the connected pore space. The effective pore volume is obtained from Boyle's Law using the pressure before and after introduction of helium, and the reference volume.
Industry:Oil & gas
A technique for measuring the fluid saturations in a core sample by heating the sample and measuring the volumes of water and oil driven off. The sample is crushed and weighed before being placed in the retort. It is then heated in stages or directly to 650<sup>o</sup>C (1200<sup>o</sup>F) during which the fluids are vaporized, collected, condensed and separated. Plateaus in the rise of the cumulative water volume with temperature are sometimes analyzed to indicate when free water, surface clay-bound water and interlayer clay-bound water have been driven off. <br><br>The volumes of water and oil are measured directly, but corrections are needed to account for alterations in the oil. The volume of gas also is needed for accurate results. This is measured on a separate, adjacent sample by injecting mercury under pressure and measuring the volume absorbed. Before injection, the sample is weighed and its bulk volume determined by mercury displacement. The total pore volume is then the sum of the volumes of gas, oil and water. The saturation of each component is the ratio of its volume to the total pore volume.
Industry:Oil & gas
A technique for measuring the effect of pits and holes in the inner wall of a casing on a high-frequency electrical signal induced in the casing. The eddy-current measurement is used in conjunction with a flux-leakage measurement to determine casing corrosion, the latter being sensitive to the defects on both the inner and outer walls. <br>The principle of measurement is similar to the openhole induction log, but at higher frequencies. A transmitter coil produces a magnetic field that induces eddy currents in the casing wall. These currents generate their own magnetic field that induces a signal in two closely spaced receiver coils. In smooth casing, these signals are the same, but if the inner wall is pitted, the signals are different. Transmitter-receiver combinations are placed on multiple pads applied against the casing at several azimuths to fully cover the casing wall.
Industry:Oil & gas
A technique for measuring the effective porosity of a core sample by summing the volumes of the fluids recovered from it. The volumes of the gas, oil and water in the sample usually are determined by the retort method, which also determines the bulk volume. The porosity is then the ratio of the total fluid volume to the bulk volume.
Industry:Oil & gas
A technique for measuring the bulk volume of a core sample by submerging it in a bath of mercury and observing the increase in weight of the bath, following Archimedes principle. The bulk volume is calculated from the increase in weight divided by the density of mercury at the temperature of the bath. The sample must not touch the side of the bath and be only a few millimeters below the surface. Mercury is used because it is so strongly nonwetting and therefore does not enter the pore space. <br><br>Other, less toxic, liquids may be used in the bath, such as brine, refined oil or toluene. In this case, the sample must be fully saturated with the liquid before immersion. In an alternative method, the saturated sample is weighed in air and then again once immersed. The bulk volume is then the difference in weight divided by the density of the liquid used.
Industry:Oil & gas
A technique for measuring the bulk volume of a core sample by observing the displacement of mercury in a chamber. The chamber is first filled to a reference level and the volume recorded. The sample is introduced and the new volume recorded. The difference is the bulk volume of the sample. If the sample is weighed, its bulk density can also be calculated. Mercury is used because it is strongly nonwetting and therefore does not enter the pore space.
Industry:Oil & gas
A technique for measuring formation resistivity between two or more wells. This technique measures the signal between an electromagnetic induction transmitter in one well, and a receiver array located in another well. The transmitting antenna broadcasts a continuous sinusoidal signal at programmable frequencies. Tomographic processing creates a map of resistivity of the area between the wells. Measurements acquired by this technique have a greater depth of investigation than conventional logging tools and are sensitive to fluid content. Crosswell electromagnetic induction surveys fill an intermediate role between high-resolution well logs and lower-resolution surface measurements. Asset managers utilize crosswell electromagnetic surveys for a variety of applications, such as monitoring sweep efficiency, identifying bypassed pay, planning infill drilling locations and improving the effectiveness of reservoir simulations.
Industry:Oil & gas
