An experimental investigation on Archie parameters at ambient and overburden conditions of clean reservoir rocks.

Al-Mahtot, Omran Bahri

Abstract

This thesis presents an experimental investigation of the effect of overburden pressure, porosity type and experimental conditions on the electrical properties (Archie's parameters) of clean reservoir rocks. The samples were from sandstone formations (North Sea), and carbonate formations (Sirte Basin, Libya). Although much work has been carried out on the electrical properties of sandstones (which are considered as ideal representatives of clean reservoir rocks) few experimental studies have been made for carbonate rocks. The continuous injection technique was used to study the effects of flow displacement mechanisms and fluid characteristics on the resistivity-saturation relationships for both sandstone and carbonate samples. The results showed that the saturation exponent is dependent on both the injection rate of the displacing phase and the fluid viscosities, and it is demonstrated that large errors in water/hydrocarbon saturation can arise if conditions used for the core analysis differ widely from those in the formation. The classical Archie's equation does not take into account the effects of these variables, and therefore it is recommended that the saturation exponent to be used in log analysis should be evaluated with great caution. The Archie's equation parameters of carbonate rocks were found to vary with porosity type. Samples with mainly interparticle porosity type had m = 2, while moldic and/or vuggy samples gave higher values, and n was found to be only weakly dependent on porosity type. These results are of particular significance, as little work has previously been carried out on carbonate rocks, which show greater variations in porosity type than the sandstones which have been studied in considerable detail. Measurements of the effect of overburden pressure showed that this has a significant effect on the values of the Archie parameters, depending on rock type and pressure applied, as well as on rock porosity. A better understanding of the mechanism of this effect has been achieved which will aid in improved formation evaluation. The study has permitted a critical evaluation of the applicability of Archie's equation for different experimental conditions and rocks of different porosity types. It has been demonstrated that the equation has significant limitations and its applicability depends to a major extent on the experimental conditions used in core analysis.

Citation

AL-MAHTOT, O.B. 1999. An experimental investigation on Archie parameters at ambient and overburden conditions of clean reservoir rocks. Robert Gordon University, PhD thesis. Hosted on OpenAIR [online]. Available from: https://doi.org/10.48526/rgu-wt-2807275

• Thesis Type: Thesis
• Deposit Date: May 5, 2025
• Publicly Available Date: May 5, 2025
• DOI: https://doi.org/10.48526/rgu-wt-2807275
• Keywords: Sandstone; Carbonate rocks; Porosity; Electrical properties; Oil and gas reservoirs; Reservoirs
• Public URL: https://rgu-repository.worktribe.com/output/2807275
• Related Public URLs: https://rgu-repository.worktribe.com/output/2829788 (Supplementary data)
• Additional Information: The file accompanying this record contains the main text of the thesis and the contents of Appendix A. The contents of Appendices B through D were originally on a floppy disk and have been preserved as supplementary data in a separate record: https://rgu-repository.worktribe.com/output/2829788
• Award Date: Jun 30, 1999