- 行业: Oil & gas
- Number of terms: 8814
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A wireline log of the yields of different elements in the formation, measured using induced gamma ray spectroscopy with a pulsed neutron generator. The elemental yields are derived from two intermediate results: the inelastic and the capture spectrum. The inelastic spectrum is the basis for the carbon-oxygen log, and can also give information on other elements. The capture spectrum depends on many elements, mainly hydrogen, silicon, calcium, iron, sulfur and chlorine. Since the elemental yields give information only on the relative concentration of elements, they are normally given as ratios, such as C/O, Cl/H, Si/(Si + Ca), H/(Si + Ca) and Fe/(Si + Ca). These ratios are indicators of oil, salinity, lithology, porosity and clay, respectively. To get absolute concentrations, it is necessary to calibrate to cores or, more often, use a model such as the oxide-closure model. <br><br>The depth of investigation of the log is several inches into the formation. It can be run in open or cased hole. Pulsed neutron spectroscopy logs were introduced in the mid 1970s after a decade or more of investigation.
Industry:Oil & gas
A wireline log run to provide a means of depth correlation by comparing the position of casing collars to the reference log (gamma ray log). A short casing joint generally is run near the area to be perforated to assist in the correlation process.
Industry:Oil & gas
A wireline log of the concentration by weight of aluminum in the formation, based on the principle of neutron activation. Aluminum (<sup>27</sup>Al) can be activated by capturing relatively low-energy neutrons from a chemical source to produce the isotope <sup>28</sup>Al, which decays with a half-life of 2. 3 minutes and emits a relatively easily detected 1. 78 MeV gamma ray. A natural gamma ray spectrometer will detect this gamma ray along with the other natural gamma rays. If the natural gamma spectrum has been measured before activation, it can be subtracted from the spectrum after activation to give an estimate of Al content. <br><br>Al is a relatively direct indicator of the volume of clay, since clay minerals are alumino-silicates.
Industry:Oil & gas
A widespread marine flooding surface that separates the underlying transgressive systems tract from the overlying highstand systems tract. The surface also marks the deepest water facies within a sequence. The maximum flooding surface represents a change from retrogradational to progradational parasequence stacking patterns. It commonly displays evidence of condensation or slow deposition, such as abundant burrowing, hardgrounds, mineralization and fossil accumulations. On wireline logs, the shales that immediately overlie the maximum flooding surface commonly have different characteristics than other shales and can often be recognized on the basis of resistivity, gamma ray, neutron and density logs. These shales can also be recognized by electrofacies analysis when the analysis is designed to do so.
Industry:Oil & gas
A well-stimulation operation in which acid, usually hydrochloric (HCl), is injected into a carbonate formation at a pressure above the formation-fracturing pressure. Flowing acid tends to etch the fracture faces in a nonuniform pattern, forming conductive channels that remain open without a propping agent after the fracture closes. <br><br>The length of the etched fracture limits the effectiveness of an acid-fracture treatment. The fracture length depends on acid leakoff and acid spending. If acid fluid-loss characteristics are poor, excessive leakoff will terminate fracture extension. Similarly, if the acid spends too rapidly, the etched portion of the fracture will be too short. The major problem in fracture acidizing is the development of wormholes in the fracture face; these wormholes increase the reactive surface area and cause excessive leakoff and rapid spending of the acid. To some extent, this problem can be overcome by using inert fluid-loss additives to bridge wormholes or by using viscosified acids. Fracture acidizing is also called acid fracturing or acid-fracture treatment.
Industry:Oil & gas
A well-servicing unit for slickline, wireline or coiled tubing operations that is equipped with a mast rather than a crane or gin pole. The mast provides a means of lifting and stabilizing tools, and running pressure-control and other equipment.
Industry:Oil & gas
A well-intervention operation conducted with equipment and support facilities that precludes the requirement for a rig over the wellbore. Coiled tubing, slickline and snubbing activities are commonly conducted as rigless operations.
Industry:Oil & gas
A wellhead component or a profile formed in wellhead equipment in which the casing hanger is located when a casing string has been installed. The casing bowl incorporates features to secure and seal the upper end of the casing string and frequently provides a port to enable communication with the annulus.
Industry:Oil & gas
A wellhead component that supports the tubing hanger and provides a means of attaching the Christmas tree to the wellhead.
Industry:Oil & gas
A wellhead component used in flanged wellhead assemblies to secure the upper end of a casing string. Casing spools or bowls are available in a wide range of sizes and pressure ratings and are selected to suit the specific conditions.
Industry:Oil & gas
