Robert C. Ransom
What are Archie’s Basic Relationships
What is Meant by the Plot of Rt versus Swtϕt
Parallel Resistivity Equations Used in Resistivity Interpretation
What is the Formation Resistivity Factor
Table of Retrievable Contents:
A CLARIFYING CONCEPT OF ARCHIE'S RESISTIVITY RELATIONSHIPS AND PARAMETERS.
A MODEL AND DISCUSSION
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Figure 1. A graphical representation of the model. In this diagram the model illustrates oil-bearing sandstone. Rt varies with oil saturation and distribution. Exponent n varies with the electrical interference caused by the presence of oil regardless of saturation. Swt is determined by the intersection of the slope representing n with level Rt . See text for full explanation. Based on Ransom (1974,1995).
Figure 2. A detailed portion of the graphical model showing how Rwe results from a mixture of waters Rw and Rwb in a shaly sand. The effect of the more conductive pseudo water represented by Rwb produces the typical a multiplier of Rw . Exponent m is an intrinsic property of the rock. Based on Ransom (1974).
Figure 3. An insulating cube with a 20% void filled with water. Electrical-survey current is flowing through the cube from top to bottom. This cube is a visual aid in the development of the formation factor. See text for discussion. From Ransom (1984, 1995).
Figure 4. A crossplot illustrating the iteration of Swt for the value of Swt that satisfies both sides of Equation (4b). See the text for discussion.
Figure 5. The crossplot of Rwa versus Clayiness where the identified trend is extrapolated in both directions to evaluate Rw and Rwb at 0% and 100% clayiness, respectively. See text for discussion. From Ransom (1995), courtesy of John Wiley & Sons, Inc.
