Implication of an Integrated Approach to the Determination of Water Saturation in a Carbonate Gas Reservoir Located in the Persian Gulf

Document Type: Research Paper

Authors

1 Department of Geophysics, College of Basic Science, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran

2 Department of Petroleum Engineering, Islamic Azad University, Science and Research Branch, Tehran, Iran

3 Department of Petrophysics, Iranian Offshore Oil Company, Tehran, Iran

Abstract

Water saturation determination is one of the most important tasks in reservoir studies to predict oil and gas in place needed to be calculated with more accuracy. The estimation of this important reservoir parameter is commonly determined by various well logs data and by applying some correlations that may not be so accurate in some real practical cases, especially for carbonate reservoirs. Since laboratory core analysis data have a high accuracy, in this study, it is attempted to use core and geological core description data to present an improved method to determine an optimized cementation factor (m) and a saturation exponent (n) in order to evaluate water saturation within carbonate reservoirs compared to default values (m=2, n=2, a=1) in a carbonate gas reservoir located in the Persian Gulf. Based on integrating core petrography and velocity deviation log (VDL), core samples were classified based on the type of porosity and geology description, and then by employing log-log plots of formation resistivity factor (FRF) versus porosity and formation resistivity index (FRI) versus water saturation, saturation parameters (m,n) were determined for each classification. Utilizing default and optimized values of saturation parameters, water saturation logs were obtained through different conductivity models by employing Multi min algorithm. Then, optimized water saturation was compared to core data. Error analysis showed that water saturation data resulted in optimized saturation parameters having a lower average error of 0.08 compared to the default ones with an average error of 0.14, and based on cumulative histogram, optimized water saturation data are in good agreement with the trend of core water saturation.

Keywords


Archie G. E., “The Electrical Resistivity Log as an Aid in Determining Some Reservoir Characteristics,” Transactions of AIME, 1941, 146, 54-62.

Worthington P. F., “The Evolution of Shaly-sand Concepts in Reservoir Evaluation,” The Log Analyst, 1985, 26, 23-40.

Hossin A., “Calcul des Saturations en Eau par la Methode du Ciment Argileux,” Bulletin de l’Association Francaise des Techniciens du Petrole, 1940

Simandoux P., “Mesures Dielectriques en Milieu Poreux, Application a la Mesure des Saturations en Eau,” Etude du Comportement des Massifs ArgileuxRevue, IFP Supplementary Issue, 1963.

Bardon C. and Pied B., “Formation Water Saturation in Shaly Sands,” Trans. SPWLA 10th Annual Logging Symposium, 1969.

Poupon A. and Leveaux. J., “Evaluation of Water Saturation in Shaly Formations,” SPWLA 12th Annual Logging Symposium, 1971.

Waxman M. H. and Smiths L. J. M., “Electrical Conductivities in Oil-bearing Shaly Sands,” Society of Petroleum Engineers Journal, 1968, 8, 107-122.

Clavier C., Coates G., and Dumanoir J., “The Theoretical and Experimental Bases for the Dual Water Model for the Interpretation of Shaly Sands,” Paper SPE 6859, 1977.

Aguilera R., “Analysis of Naturally Fractured Reservoirs from Conventional Well Logs”, Journal of Petroleum Technology, 1976, 28, 764-772.

Borai, A. M., “A New Correlation for the Cementation Factor in Low-porosity Carbonates,” SPE Formation Evaluation, 1987, 2, 495-499.

Lucia F. J., “Carbonate Reservoir Characterization,” Springer, 1999, 226.

Ragland D. A., “Trends in Cementation Exponents (m) for Carbonate Pore Systems,” Petrophysics, 2002, 43, 434-446.

Rezaee M. R., Motiei H., and Kazemzadeh E., “A New Method to Acquire m Exponent and Tortuosity Factor for Microscopically Heterogeneous Carbonates,” Journal of Petroleum Science and Engineering, 2007, 56(4), 241-251.

Towel G., “An Analysis of the Formation Resistivity Factor-porosity Relationship of Some Assumed Pore Geometries,” in 3rd Annual Logging Symposium Transactions, SPWLA, 1962.

Focke J. W. and Munn D., “Cementation Exponent in Middle Eastern Carbonate Reservoirs,” SPE Formation Evaluation, 1987, 155-167.

Hamada G. M., Almajed A. A., and Okasha T. M., “Uncertainty Analysis of Archie’s Parameters Determination Techniques in Carbonate Reservoirs,” Journal of Petroleum Exploration and Production Technology, 2013, 3, 1-10.

Sethi D. K., “Some Considerations about the Formation Resistivity Factor-porosity Relations,” 20th SPWLA Symposium, 1979.

Rafiee S., Hashemi A., and Shahi M., “A New Cementation Factor Correlation in Carbonate Parts of Southwest Iranian Oil Fields,” Electronic Scientific Journal Oil and Gas Business, 2013, 2, 227-251

Asadollah M., Keramati M., Bagheri A. M., and Haghighi M., “Investigation of the Effect of Cementation Factor on OOIP in an Iranian Carbonate Reservoir,” GEO 2006 Middle East Conference and Exhibition, 2006.

Wyllie M. R. J. and Gregory A. R., “Formation Factors of Unconsolidated Porous Media: Influence of Particle Shape and Effect of Cementation,” Journal of Petroleum Technology, 1953, 5, 103–110.

Anselmetti F. S. and Eberli G. P., “The Velocity-deviation Log: a Tool to Predict Pore Type and Permeability Trends in Carbonate Drill Holes from Sonic and Porosity or Density Logs,” AAPG Bull, 1999, 83, 450–66.

Brie A, Johnson D. L. and Nurmi R. D., “Effect of Spherical Pores on Sonic and Resistivity Measurements,” Society of Professional Well Log Analysts 26th Ann. Logging Symp, 1985

Eberli G. P., Anselmetti F. S., and Incze M. L., “Factors Controlling Elastic Properties in Carbonate Sediments and Rocks,” The Leading Edge, 2003, 22, 654–60

Kazemzadeh E., Nabi-Bidhendi M., Keramati Moezabad M., Rezaee M. R. and Saadat K., “A New Approach for the Determination of Cementation Exponent in Different Petrofacies with Velocity Deviation Logs and Petrographical Studies in the Carbonate Asmari Formation,” Journal of Geophysics and Engineering, 2007, 4, 160-170.