- Industry: Oil & gas
- Number of terms: 8814
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A recording of the in-situ rate of fluid flow at different depths in a well, normally one completed for production or injection. The flow profile is a log recorded in a unit such as barrels per day, or as a percentage of the total flow from the reservoir in a production well or into the reservoir in an injection well. In single-phase flow, the profile can be determined from a flowmeter. In multiphase flow, it is desirable to show the flow rates of each of the phases, in which case a holdup log and either a flowmeter or a phase velocity log are needed.
Industry:Oil & gas
A refinery unit used to improve or upgrade heavy oil to produce higher-quality hydrocarbon liquids or upgraded synthetic crudes. The refining unit may include any combination of the following: hydrogen addition processes, carbon rejection processes or carbon concentration and removal processes.
Industry:Oil & gas
A record of the velocity with which a particular phase (gas, oil or water) moves in a producing well. While most flowmeters measure some average of all the fluids, the phase-velocity log identifies one particular phase. This is particularly important in highly deviated and horizontal wells with multiphase flow, where the flow structure is complicated. <br><br>Phase-velocity measurements are made with either the crosscorrelation flowmeter, the water-flow log, or with chemical markers designed to mix specifically with one particular phase. Velocity-shot measurements, using radioactive tracers, have also been used. In a typical chemical marker technique, a gadolinium-rich marker is injected into the flow stream, dissolving in either oil or water. Gadolinium has a high capture cross section, or sigma, so that a slug of fluid with high sigma moves with the appropriate phase up the borehole. This slug can be detected by a standard pulsed-neutron capture tool, and the velocity of the phase computed from the time of flight between ejector and detector.
Industry:Oil & gas
A record of the velocity and direction of water flowing in and around a borehole based on oxygen activation. The log may also include estimates of the flow volume and the distance from tool to flowing water. Water, and occasionally carbon dioxide, is the only source of moving oxygen in and around the borehole. Hence, water flow can be detected by oxygen activation, which, being a nuclear technique, is sensitive to flow inside and outside the casing. The measurement is sensitive to small flows, and can be configured to measure upward or downward flow. It is particularly useful as a leak and channel detector, to identify locations of water entry or exit and as a measurement of water velocity in multiphase flow. Logs may be continuous, but the most accurate measurements are made with the tool stationary. <br><br>Although first tried in the 1960s, the log was not fully studied and implemented until the late 1970s with a purpose-built experimental tool. Standard pulsed-neutron spectroscopy tools were modified to record the log in the 1980s.
Industry:Oil & gas
A record of the temperature gradient in a well. The temperature log is interpreted by looking for anomalies, or departures, from the reference gradient. This reference might be the geothermal gradient, a log recorded before production started or a log recorded with the well shut-in. Most anomalies are related to the entry of fluids into the borehole or fluid exit into the formation. Since the temperature is affected by material outside the casing, a temperature log is sensitive to not only the borehole but also the formation and the casing-formation annulus. <br><br>Temperature logs have many applications, with the most common being to identify zones producing or taking fluid, to evaluate a cement or hydraulic fracture treatment, and to locate lost circulation zones and casing leaks. Since temperature takes time to dissipate, a temperature log tends to reflect the behavior of a well over a longer time period than other measurements.
Industry:Oil & gas
A record of the sound measured at different positions in the borehole. Since fluid turbulence generates sound, high noise amplitudes indicate locations of greater turbulence such as leaks, channels and perforations. Noise logging is used primarily for channel detection, but has also been used to measure flow rates, identify open perforations, detect sand production and locate gas-liquid interfaces. The log may be either a continuous record against depth or a series of stationary readings. The log may indicate the total signal over all frequencies, the signal at a single frequency, or consist of a set of logs for different frequency ranges. Different frequency ranges can be tied to different sources of noise or different flow regimes. <br><br>Although first introduced around 1955, the technique was not used commercially until after laboratory studies in the early 1970s.
Industry:Oil & gas
A record of the quantity of different radioactive isotopes near the borehole. The technique used is the same as for natural gamma ray spectroscopy, but measures the quantities of various short half-life radioactive tracers in addition to natural gamma rays. The log is run to monitor the results of processes that can be tagged, for example, hydraulic fracturing, gravel-pack placement, squeeze cementing, acid treatment and lost-circulation detection. Different radioactive tracers are added at different stages of the process so that by measuring the different tracers, it is possible to track the development, for example, of the fracture. The most common radioactive tracers are <sup>110</sup>Ag (silver), <sup>195</sup>Au (gold), <sup>135</sup>I (iodine), <sup>192</sup>Ir (iridium), <sup>124</sup>Sb (antimony), and <sup>46</sup>Sc (scandium).
Industry:Oil & gas
A record of the quality of a gravel pack and the quantity of solid particles it contains. The traditional logging technique uses a type of nuclear fluid densimeter, with a gamma ray source and a single detector. The number of gamma rays reaching the detector is inversely proportional to the gravel-pack density. The count rate is used qualitatively, being scaled in each well between zones with 100% pack and zero pack, or else compared before and after a repair to the pack. <br><br>The density measurement is not entirely independent of the formation, and is not effective when the density of the particles and the completion fluid are similar. In these cases, a neutron activation or neutron-porosity measurement may be used. Other techniques include a neutron porosity log and tracer measurements. Radioactive tracers may be coated on the outside of the particles or else included within the particles. They can be detected by gamma ray logs, or if a variety of tracers is used they can be tracked with a multiple-isotope log.
Industry:Oil & gas
A record of the presence of tracer material placed in or around the borehole to measure fluid movement in injection wells. There are two traditional techniques for recording radioactive-tracer logs: the tracer-loss measurement, in which a tracer material is added to the completion fluid and its progress monitored with a gamma ray tool; and the velocity-shot measurement, in which the tracer is ejected from one part of a production logging tool and its progress monitored by one or more gamma ray detectors farther down the tool. <br><br>Radioactive-tracer logs are used to determine injection-flow profiles and detect channels or leaks. They may also be used in production wells, but care must be taken to isolate the fluids on surface until the tracer has decayed to safe levels. The tracer is a radioactive isotope that is soluble in water, oil or gas, or else insoluble, as in the bead tracer. Different radioactive elements with distinct energies and lifetimes may be used. Today, for water injection, the most common is a water-soluble iodine tracer that has a half-life of 8. 1 days, while for steam injection a gas with krypton is used.
Industry:Oil & gas
A record of the fractions of different fluids present at different depths in the borehole. Various techniques are used to measure these fractions. The earliest techniques measured the fluid density, using a gradiomanometer or a nuclear fluid densimeter, or the dielectric properties, as in the capacitance or water-cut meter. <br><br>While these techniques were satisfactory in near-vertical wells with two-phase flow, they were often found to be inadequate in highly deviated and horizontal wells, where flow structures are complex. More recent developments are based on the use of multiple local probes to detect bubbles of gas, oil or water, and on a combination of nuclear techniques usually known as three-phase holdup.
Industry:Oil & gas
