- Branża: Oil & gas
- Number of terms: 8814
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An electrode device with small spacings from which the current flow, and hence the measurement, is focused a short distance into the formation. The microcylindrical log measures the resistivity of the flushed zone with minimum influence from the mudcake or the undisturbed zone. The electrodes are mounted on a pad that is pressed against the borehole wall. The current is focused both parallel and perpendicular to the tool axis. Three measurements are made, each with a different depth of investigation. These measurements are combined to solve for the mudcake and flushed-zone resistivity.
Industry:Oil & gas
An electrode device with small spacings from which the current flow, and hence the measurement, is focused a short distance into the formation. The microspherical log measures the resistivity of the flushed zone with minimum influence from the mudcake or the undisturbed zone. The principle of spherical focusing is used. The electrodes are mounted on a pad that is pressed against the borehole wall. In a typical tool design, 90% of the signal comes from within 3 in. (7. 6 cm) of the pad, ensuring that the undisturbed zone rarely has an effect.
Industry:Oil & gas
An electrode device with small spacings from which the current flow, and hence the measurement, is focused a short distance into the formation. Introduced in 1953, the microlaterolog measures the resistivity of the flushed zone with minimum influence from the mudcake or the undisturbed zone. The central current emitting electrode (A0) is surrounded by a guard electrode that emits sufficient current to focus the current from A0 a certain distance into the formation. The electrodes are mounted on a pad that is pressed against the borehole wall. In a typical tool design, 90% of the signal comes from within 3 in. (7. 6 cm) of the pad, ensuring that the undisturbed zone rarely has an effect.
Industry:Oil & gas
An electrode device with multiple current electrodes configured in several different ways to produce several different responses. A typical array consists of a central electrode emitting survey current, with multiple guard electrodes above and below it. Current is sent between different guard electrodes to achieve greater or less focusing. The greater the focusing, the greater the depth of investigation. About five basic measurements are obtained in this way. This hardware focusing may be further improved by software focusing, in which the signals from the basic measurements are superimposed mathematically to ensure proper focusing in a wide range of conditions.
Industry:Oil & gas
An electrochemical source that provides electrical power to a downhole or surface tool used for determining the location or assisting in the extraction of hydrocarbons. Unlike a conventional battery, an oilfield battery must safely provide power sufficient to enable a tool to perform as specified, even on extended jobs. Designed with rugged external packaging to fit within a confined tool space, it must tolerate extreme temperatures while withstanding high shock and vibration. Its internal chemistry must also accommodate a long shelf life.
Industry:Oil & gas
An early scale used for the presentation of resistivity logs. The scale has two parts, equally divided about a midpoint. The left part is linear in resistivity, for example 0 on the left edge to 50 ohm-m at the midpoint. The right part is linear in conductivity, from 0 on the right to 1/50 = 20 mS/m at the midpoint. In this way, it was possible to display the complete range of resistivity in one track. It was subsequently replaced by the logarithmic scale.
Industry:Oil & gas
An early signal in a cement-bond log. In some formations, particularly carbonates of low porosity, it is possible that the first acoustic signal to arrive at the receiver passes through the formation rather than through the casing, and hence its amplitude is unrelated to the cement bond. This manifests itself by a shortening of the transmitter-to-receiver traveltime and by anomalous patterns on the variable-density log. In such cases, it may be assumed that the cement bond is good, as the signal would be unlikely to be transmitted through the formation with sufficient amplitude to be detected if cement bond were poor.
Industry:Oil & gas
An early perforating method that used a hardened steel bullet or projectile, propelled by an explosive charge, to create a perforation tunnel. This method creates a low-permeability crushed zone and leaves the bullet and associated debris jammed at the end of the tunnel. Jet perforating is now the preferred method.
Industry:Oil & gas
An assembly of pressure-control equipment that enables the running and retrieval of long tool strings on a coiled tubing string in a live wellbore. The deployment system is configured to provide two barriers against well pressure as the tool string is assembled and run into the wellbore. Once fully assembled, the coiled tubing equipment is connected and the tool string is run into the wellbore. The process is reversed for tool retrieval.
Industry:Oil & gas
An assembly of components used to contain wellhead fluids and pressure during braided-line or wireline operations. The wireline passes through a close-tolerance tube assembly as it leaves the wellbore. High-pressure grease is pumped into the surrounding annulus to effect a pressure-tight dynamic seal that is maintained during the operation by injecting more grease as required. A slight leakage of grease is normal, and the addition of fresh grease enables the consistency of the seal to be maintained at an effective level.
Industry:Oil & gas
