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Heavy oil is considered an important alternative for traditional fossil fuels. Exploring and developing heavy oil reservoirs require time-lapse seismic data for dynamic monitoring of the reservoir elastic parameters and determining of the temperature field to evaluate the fluidity of the heavy oil. The key is establishing a relationship between the temperature and seismic elastic parameters to convert the elastic field into a temperature field. Therefore, a temperature-dependent rock physics model for heavy oil sand must be established. In this study, we investigated the temperature-dependent elastic wave velocities of natural and artificial heavy oil sands. The modified contact cement theory and the solid Gassmann equation were combined to construct a temperature-dependent rock physics model. The proposed model can predict variations in elastic wave velocities along with temperature changes in both natural and artificial heavy oil sands. Based on the model results, we propose a possible mechanism for the temperature-dependent elastic wave velocity of heavy oil sands, namely, the weakening of heavy oil cementation is the main controlling factor in the elastic wave velocity sensitivity of heavy oil sands. A temperature-dependent rock physics template (TDRPT) is proposed to diagnose the temperature, and the diagnostic results were verified using natural heavy oil sands. Our proposed model and TDRPT are essential tools to guide the thermal production of heavy oil reservoirs. • Temperature-dependent rock physics template proposed to diagnose temperature. • Modified contact cement theory and solid Gassmann equation combined in model. • Heavy oil cementation weakening controls elastic wave velocity of heavy oil sands. [ABSTRACT FROM AUTHOR]

Understanding the relationship between compressional and shear wave velocities and their anisotropic characteristics in self-resourcing reservoir shales is of considerable interest for petrophysical, geophysical, and geomechanical applications of unconventional resources exploration and production. We compile laboratory measurements on the ultrasonic velocity of known shale reservoirs worldwide. Their compressional and shear wave velocities propagating in the vertical and horizontal directions can be characterized by a linear model with the coefficients of determination (R2) close to 0.9. The P-to-S-wave velocity ratio in the vertical direction is overall higher than that in the horizontal direction. The P-to-S-wave velocity ratio decreases with decreasing P-wave velocity due to the increasing organic matter content and hydrocarbon-filled porosity. Mineralogy influences the relationship between compressional and shear wave velocities to a minor degree. Carbonate-rich shales have a higher P-to-S-wave velocity ratio than silica-rich shale when the P-wave velocity is lower than 4 km/s and a lower ratio when the P-wave velocity is higher than 5 km/s. By employing anisotropic fluid substitution, we justify that the model derived from the laboratory measurements can apply to shale reservoirs containing gas or volatile oil. We apply the linear models to predict the shear wave velocity in two vertical wells of shale reservoirs. The predictions of shear wave velocity in the targeted reservoirs have less than 3% errors, demonstrating that the proposed linear models, to the first order, can predict shear wave velocity in unconventional shale reservoirs. • P- and S-wave velocity relationships in anisotropic organic shales are characterized with a linear model. • P-to-S wave velocity ratio decreases with decreasing P-wave velocity due to the increasing TOC and porosity. • The linear relationship is applicable for prediction of S-wave velocity in shale reservoir containing volatile oil and gas. [ABSTRACT FROM AUTHOR]