Empirical Modeling of the Saturated Shear Modulus in Heavy Oil Saturated Rocks
Date
2018-01-25
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Abstract
Seismic reservoir characterization and monitoring require the knowledge of seismic wave velocities and their dependencies on reservoir properties and production induced changes. Many attempts have been done to investigate the seismic properties of heavy oils and to model their effects on seismic rock properties. In heavy oil saturated rocks in cold temperatures, due to non-zero shear rigidity of the oil, observed P- and S-wave velocities are higher than Gassmann’s predicted velocities. The Ciz and Shapiro model generally underestimates the saturated shear modulus at cold temperatures. Appropriate modeling of the saturated shear modulus can greatly enhance the accuracy of quantitative interpretation of spatial fluid saturation and temperature distribution within the reservoir through production. The apparent shear modulus of heavy oils depends on their density, temperature and the frequency of the measurements. Using modulus-temperature cross plots of a well log data set of an Athabasca heavy oil play, the existence of the liquidation temperature and apparent shear modulus of the heavy oil is verified. Two empirical relationships are proposed to predict the shear and bulk moduli of extra heavy oils at different reservoir conditions from seismic to ultrasonic frequencies. Using measured viscosities of core samples, an empirical model is proposed which uses apparent shear modulus of the oil, its saturation, porosity and dry shear modulus to estimate saturated shear modulus of the rock. The model is calibrated to ultrasonic lab measurements. Comparing its results with available literature data supports the validity of the model. The behavior of the model with respect to input parameters, the range of its applicability and theoretical limitations are also discussed. The observed weakening of the shear moduli at temperatures above 100°C is attributed to thermal expansion of the rock and its effect on effective pressure.
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Keywords
heavy oil, shear modulus, frequency, temperature, seismic monitoring, rock physics
Citation
Javanbakhti, A. (2018). Empirical Modeling of the Saturated Shear Modulus in Heavy Oil Saturated Rocks (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/5444