Sensitivity Analysis of Sandstone Rock Elastic Properties to Effective Pressure Using a New Rock Physics Workflow and It
Sensitivity analysis of sandstone rock frame to pressure has been an appealing area of research in upstream oil and gas industry. Knowledge of the effects of various pressures on sandstone elastic properties has been used to interpret 3D seismic data and
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Abstract Sensitivity analysis of sandstone rock frame to pressure has been an appealing area of research in upstream oil and gas industry. Knowledge of the effects of various pressures on sandstone elastic properties has been used to interpret 3D seismic data and also to use time-lapse seismic data sets to monitor the dynamic changes in an oil and gas reservoir. Rock physics models build a relation between rock elastic properties and reservoir pressure; therefore, two rock physics approaches are used commonly to illustrate the dependency of rock elastic parameters to pressure. The first approach is empirical equations, and the second is to use contact theory models. Laboratory-derived empirical equations are used to relate rock elastic properties to pressure variations. Besides these equations, contact theory models also are used to investigate the sandstone rock elastic properties to pressure changes. The aim of this research is to present a new rock physics workflow to predict the effect of different pressures on dry sandstone rock elastic properties. Hertz–Mindlin contact theory in conjunction with the pore space stiffness theory is cooperated to model the pressure effects on dry rock seismic properties. This new rock physics workflow is calibrated with laboratory measurements on core samples. The results of the developed rock physics workflow show a perfect fit with the pressure laboratory measurements on core samples. Unlike other contact theory rock physics models, our workflow requires less time with a straightforward approach. An application of this rock physics workflow for time-lapse seismic feasibility modeling is also included in this research. Keywords 4D seismic data
Rock physics model Pressure sensitivity analysis
S. Danaei (&) D. Ghosh Department of Geosciences, Faculty of Geosciences and Petroleum Engineering, Universiti Teknologi PETRONAS, 31750 Tronoh, Perak, Malaysia e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2017 M. Awang et al. (eds.), ICIPEG 2016, DOI 10.1007/978-981-10-3650-7_4
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1 Introduction Seismic wave propagation into oil and gas reservoir rock depends on various factors, namely lithology, porosity, temperature, and reservoir pore fluid. These factors control the elastic properties of the reservoir rock and therefore alter the seismic responses significantly. Any changes in reservoir pore fluid saturation and pressure induced by production and/or injection will affect seismic velocity. Fluid saturation and pressure changes are among the most important changes observed at the location of oil and gas reservoirs. These changes need to be analyzed, and the effects should be modeled in great details. The effect of fluid saturation changes on seismic velocity is investigated comprehensively by different researchers. The most commonly used theoretical approach for fluid saturation changes employs the low-frequency Gassmann fluid substitution theory [1]. On the other hand, the effect of pore pressure changes is less understood. R
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