The laterolog was put into service in , predating the induction log by 6 or 7 years, Logarithmic scales appeared for the dual laterolog and later tools to. Dual laterolog resistivity measurements; Laterolog anomalies; Azimuthal dual laterologs. 2 Array electrode tools; 3 Shallow focused. Description. The QLDLL3 Dual Laterolog tool provides a time multiples dual spacing focused resistivity measurement with two different.
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Drillpipe conveyance produces the same effect, with the drillpipe becoming the “short circuit. The Schlumberger Geovision Resistivity GVR tool  is an electrode resistivity tool that laterrolog five resistivity values—bit, ring, and three button resistivities—as well as gamma-ray and shock measurements. Auxiliary measurements are made that are very shallow, with current paths close to the tool.
There are four focused-resistivity measurements incorporated in the RAB tool.
Electrode resistivity devices
The tool records azimuthal resistivity variations around the borehole and produces an image of the variations. The current switch is changed to position 2.
Measurements with the following features should be chosen: Now a current from inside the tool is sent from the upper electrode to a lower electrode. Leave a Reply Cancel reply Your email address will not be published. The apparent resistivities RLA1 through RLA5 are all sensitive to the formation, becoming progressively deeper in investigation.
Dual Laterolog Tool (EDLT) | LandSea – Open Hole and Cased Hole Logging Systems
The “geometric factor” relates the effect of a portion of formation on the logging tool reading to its position relative to the tool in an infinite homogeneous medium. A mild Groningen effect may be difficult to identify from the LLd curve alone. A beam thickness of only 28 in.
The current is injected into the casing and dua, to an electrode in the earth some distance from the casing. These recordings are used for correlation of the strata and detection and quantitative evaluation of possibly productive horizons. Long guard electrodes are required to achieve the desired depth of investigation and measurement range.
The resistivity at the bit is derived from the axial current, which is measured by a ring monitor toroid, and the induced voltage, which is a function of the transmitter current.
Low-impedance circuits measure the current at each button electrode, and the axial current flowing down the collar is measured at the ring electrode by the ring monitor toroid and at the lower transmitter by the lower monitor toroid. To estimate R t under a variety of different logging conditions and in different formations, a simple three-parameter, step-profile invasion model is often used. Because the borehole is generally more conductive than the formation, the current tends to stay in the mud, and the measurement responds primarily to the volume of mud in front of each azimuthal electrode.
The shoulder-bed and invasion responses of laterolog tools are combined in the tool response in ways that are difficult to separate. Current-return electrode B is at a great distance above A or at the surface. Laterolog tools are resistivity devices, which are most accurate in medium- to high-resistivity formations. Real-time corrections can be made duao Groningen effect, electrical path changes imposed by tough logging conditions TLC logging in which the logging tool is transported on drillpipe, and borehole effects.
Conversely, a laterolog tool is preferred when R xo is less than R t. The idea originated in the s  and was revisited by Kaufman  and Vail  in the late s. The shallowest mode, RLA0, is mostly sensitive to the borehole and is used to estimate the mud resistivity.
Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro. Cased-hole resistivity is becoming accepted for applications including contingency logging, reservoir monitoring, and evaluation of old producing wells. Your email address will not be published. The good spread in radial characteristics of the LLd and LLs measurements enables accurate resistivity analysis over a wide range of invasion conditions.
This is equivalent to replacing the azimuthal electrodes with a single cylindrical electrode of the same height. See the section on invasion interpretation for more details on the determination of Lateroloog tR xoand d i. This model consists of a flushed zone of resistivity R xo and a sharp boundary at diameter d iwith the uninvaded laterolot of resistivity R t.
Conductivity in the borehole has a strong influence on an induction measurement, but little influence on a laterolog measurement. The point of measurement is midway between A and M.
Dual Laterolog Service
The focussing allows excellent true formation resistivity measurement and good vertical duao of thin beds. The six modes are focused by a combination of hardware and software focusing. In addition to providing a visual image of formation lamination and anisotropy, the azimuthal images can be used to estimate the gross formation dip and to correct deep resistivity measurements in dipping beds.
All signals are measured at the same time and logging position.
In the early s, a new dual laterolog that had an additional azimuthally segmented current electrode was introduced. In an alternate version of the lateral, the positions of the current and voltage electrodes are interchanged.
Borehole and shoulder effects are minimized by the use of laterolog-style focusing. The azimuthal resistivity measurements are sensitive to tool eccentering in the borehole and to irregular borehole shape. Since then, new logging methods have been developed to measure values much closer to R xo and R t.
The leakoff current is determined by measuring the voltage drop along a section of the casing. The measurement is therefore sensitive to borehole size and shape and to eccentering of the tool in the borehole. Current from the upper transmitter flows down the collar and out into the formation, leaving the collar perpendicular to its surface and returning to the collar above the transmitter.
If automatic corrections are not available, log-interpretation charts provided by the service company are used to manually correct the log readings for these influences. Laterolog devices see the more resistive zones, and induction tools see the more conductive zones.
The LLs and LLd measurements have the same vertical resolution, but the Duxl device uses a less constrained focusing condition in which the focusing current returns to electrodes on the array instead of to a lateroloog electrode. However, in layered formations, there is a tendency for current to flow preferentially in the more conductive beds and avoid the more resistive beds.
These are lateroolg as inputs to a 2D inversion to solve for formation resistivities. For latefolog devices Fig.