ABSTRACT
Most prominent resistivity analysis methods are founded on Archie’s relationships. Relative to these relationships and their parameters, Archie’s relationships are surrounded by opinion. It is not the diversity, but the conflict in opinions appearing in literature that is the motivation for this paper.
A model for the interpretation of traditional resistivity well logs is developed. From that development, a philosophy for Archie's parameters emerges that is quite different from some literature in our industry, some that has been bestowed with the mantle of conventional wisdom.
In this paper, electrical law, mathematical proofs and derivations are employed in order to promote a better understanding and a better use of these relationships. Simple equations are produced in the systematic development and explanation of each of the parameters.
The classic Archie saturation equation (1942) emerges from the model presented herein, and in doing so is extended to address shaly sands and additional levels of heterogeneity and practical reservoir complexity. The concept presents in one package very basic electricity theory, simple mathematics, and the physical occurrences in nature to illustrate the mathematical and physical character of the parameters represented in Archie's basic relationships.
Additionally, it illustrates how heterogeneities such as clay shale and semi-conductive minerals influence resistivity relationships. The model further illustrates both the resistivity behavior in the presence of hydrocarbon and the problems of interpretation in partially oil-wet and oil-wet porous environments. The reality that many oil- and gas-formations are complex in terms of mineralogy, lithology and saturation distributions makes a better understanding of the analytical process imperative.
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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