Resistivity ρ, unlike resistance, is an intrinsic property of a material.It means that it doesn't matter whether the wire is thick or thin, long or short. Use Chart 3 to correct the SP.
Resistivity of the mud filtrate (R mf) at measured temperature, found on the log header.If only mud resistivity (R m) is given, convert it to R mf as explained below. The most direct way of finding water resistivity (Rw) is to obtain a sample of formation water and measure its resistivity.

Answer: Given. The following charts are required: It is assumed that ail salts in solution in the fluids are NaCl or equivalent and that the beds are clay free. Dewan, J. T., 1983, Essentials of modern open-hole log interpretation: Tulsa, OK, Penn Well Books. Figure 2 Example of a reverse SP deflection.[1]. However, this is seldom possible in practice, as formation water samples, if available, are invariably contaminated by mud filtrate. After selecting on the log the zone in which water resistivity will be determined, the formation temperature is established and the values of mud and mud filtrate resistivity are corrected accordingly. A = 0.5 m 2. Assumptions and limitations. Calculate R w from Equation (4a). Shale baseline is two divisions left of depth column. This page has been accessed 23,263 times. Resistivity-conductivity Formula Questions: 1) What is the conductivity of a wire of cooper? The ratio of the length of the resistance of P to that of Q is? Your email address will not be published.

Resistivity-conductivity Formula Questions: 1) What is the conductivity of a wire of cooper?

The data that are required include Rt (or Ro) from deep-reading resistivity tools such as deep induction (ILd) or deep laterolog (LLd) and porosity log(s). Follow the procedure below to convert Rwe to Rw. Problem 2: The length and area of wire are given as 0.2 m and 0.5 m 2 respectively. How To Calculate And Solve Questions On Resistivity. Note that an equivalent “quick look” solution can be obtained by an overlay technique using logarithmically scaled Rt and Rxo logs. Answer: Given. (3) The resistance of a 5m uniform wire of cross-sectional area 0.2 x 10-6 is 0.425 ohms. ρ 0: Original resistivity For example, at 20 °C (293 K), the resistivity of Copper at 20 °C is 1.68 * 10 -8 , it's temperature coefficient is 0.0039 K -1 , its resistivity at 30 °C is 1.75E-8. Figure 3 shows the log used in this example. Resistivity units and conductivity units. Deflections to the left of the shale line are regarded as normal or negative, and correspond to porous and permeable zones containing a more saline interstitial water than the drilling mud (Rw Rmf).

Data given: resistivity of copper at 20 o C is 1.72 x 10-8, coil length L = 100m, the cross-sectional area of the conductor is 2.5mm 2 giving an area of: A = 2.5 x 10-6 metres 2. What is the resistivity of the material of the wire? The first step in the interpretation of the SP log is the establishment of “sand” and “shale” lines, as shown in Figure 1. This article discusses the resistivity formula and its derivation. R2 = (5 X A1 X 2L1) / L1 X 0.5A1 = 10/0.5 = 20 ohms, ‘Resistivity’ = RA/L = (0.425 x 0.2 x 10-6) / 5 = 1.7 x 10-8, Recommended: Why Ammeter is connected in series and Voltmeter in parallel, a battery of 4 cell each of emf 1.5v and internal resistance 1.0ohm is connected to 1.0ohm resistor in series with a parallel combination of 2ohm resistor (a) draw the circuit diagram (b)calculate (I)combined external resistance (II)current in the circuit (III)lost voltage in the battery (IV)the current I of the 2ohm resistor, Your email address will not be published. If a clean, water-bearing zone is present or can be assumed, Rw can be calculated by using the Archie equation. Figure 4 shows an example of original and shifted logs indicating a Rt/Rmf ratio of 0.45. Join our online JAMB, Post UTME, WAEC Classes at affordable fee. The bed must be thick so that the deep investigation resistivity device is not affected by shoulder beds.

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Knowledge of the SSP is essential for the derivation of Rw, which is required for the calculation of water saturation in the uninvaded zone. For more on deriving Rt, see Preprocessing of logging data.). Required fields are marked *.

The procedure to determine Rw from the Archie equation is outlined as follows. If using an induction log, the minimum thickness should be, After correlating logs for depth mismatch, locate a clean, water-bearing zone.
Usually. On the log, establish the shale base line for the SP curve. These are arbitrary limits, with the sand lines normally representing the maximum deflection to the left and shale lines representing the maximum deflection to the right (in shales). This zone must be 100% water saturated and must not contain any clay or shale. To calculate Rw from SP, we need the following data: If the log header gives Rm only, then Rm must be converted to Rmf using this procedure: There are five steps for calculating Rw from the SP log.

All the resistivity values for various materials can be found in a table. These values are referred to as equivalent resistivities and are denoted by Rwe and Rmfe. Resistivity is a property of a material, independent of the shape and size of the specimen, while resistance depends on the size and shape of the specimen or device, as well as on its resistivity. The list below summarizes these steps, which are detailed in the rest of this section. The shale and sand lines are established, the bed boundaries on the SP curve are determined, and maximum SP inflection for that permeable bed are read off the log. Read R o (= R f) from the resistivity log, and determine the porosity from logs or otherwise. Metal Resistivity Table (2) A wire P has half the diameter and half the length of a wire Q of similar material. Resistivity formula is. Resistivity formula is. Charts supplied by logging companies permit the determination of. It then means that the resistance of a wire depends on resistivity, length, area of the wire. This method is unreliable in fractured or vuggy reservoirs.

Resistivity refers to the electrical resistance of a conductor of a particular unit cross-sectional area and unit length. An example of calculating Rw by using the SP method is as follows. The zone or permeable bed in which water resistivity is determined is selected on the log. Results can be questionable if the mud resistivity properties have varied significantly after drilling the zone to be analyzed. The parameters you must have in order to calculate include, (1) A wire of 5Ω resistance is drawn out so that its new length is two times the original length.

The resistance R is proportional to the length L and inversely proportional to the cross-sectional area A, with a proportionality factor called the resistivity of the material. The data required include the SP, the invaded zone resistivity, the formation temperature, and the mud and mud filtrate resistivities at the given formation temperature. Answer: From the resistivity-conductivity formula, we substitute the cooper resistivity which is 1.68*10 (-8) Ω*m:. Read the maximum SP response in a zone at least, Directly across from the intersection point, read R. This page was last modified on 24 November 2015, at 10:22. If this is the case, then the values obtained can be averaged. It requires a reliable measurement of Rxo. Answer: From the resistivity-conductivity formula, we substitute the cooper resistivity which is 1.68*10 (-8) Ω*m:. Calculate the total DC resistance of a 100 metre roll of 2.5mm 2 copper wire if the resistivity of copper at 20 o C is 1.72 x 10-8 Ω metre. The resistivity of a material is defined in terms of the magnitude of the electric field across it that gives a certain current density. The magnitude of deflection from the shale base line to the maximum deflection developed in a thick, clean, waterbearing sand is referred to as the static SP, or SSP. Rt and Rxo are obtained from deep and shallow resistivity logs, and Rmf is at formation temperature. Since Rmf is known, Rw can then be easily calculated. Resistance of the material; Length of the material; And the cross-sectional area of the material which is; Few Questions (1) A wire of 5Ω resistance is drawn out so that its new length is … This page has been accessed 44,017 times. (For more information on methods to derive porosity and the Archie equation, see Standard interpretation. The procedure to determine Rw from the SP is outlined as follows. If the resistivity of the wire remains the same and the cross sectional area is halved, the new resistance is, A. Click here for details, Why Ammeter is connected in series and Voltmeter in parallel, Conspiracy About 5G | Nigerian Physicist View, 27 Common Laboratory Apparatus in Schools And Uses, WAEC Physics Practical Questions And Answers – 2020 Guide, Relative Velocity In One Dimension With Examples, All Courses Offered in Nigerian Universities, Tips to Choosing Course to Study in University, RSCHST Admission Form 2020/2021 Into ND And HND, Air Force Institute of Technology Courses And Requirements, Air Force Institute of Technology Cut Off Mark 2020/2021, Ambrose Alli University Acceptance Fee 2020/2021, And the cross-sectional area of the material which is. When calculating the volume resistivity of thin films, the thickness of the layer must be known. R = 3 Ω. l = 0.2 m and. Also resistance depends on the temperature. If the mud is more saline than the formation water, the SP currents flow in the opposite direction and the corresponding deflection will be to the right of the shale line. It is quite common and good practice to determine Rw with more than one method, if possible, to check for consistency and reliability.

All the resistivity values for various materials can be found in a table. Spontaneous potential logs in water resistivity calculation, https://wiki.aapg.org/index.php?title=Spontaneous_potential_logs_in_water_resistivity_calculation&oldid=22447, Predicting the occurrence of oil and gas traps, Predicting reservoir system quality and performance, Project to the bottom of the chart to estimate R. Follow the appropriate salinity line intercepted at step 1 to the appropriate formation temperature and mark on the chart.

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