Abstract
To establish the relationship among reservoir characteristics and rock physical parameters, we construct the well-bore rock physical models firstly, considering the influence factors, such as mineral composition, shale content, porosity, fluid type and saturation. Then with analyzing the change rules of elastic parameters along with the above influence factors and the cross-plots among elastic parameters, the sensitive elastic parameters of tight sandstone reservoir are determined, and the rock physics template of sweet spot is constructed to guide pre-stack seismic inversion. The results show that velocity ratio and Poisson impedance are the most sensitive elastic parameters to indicate the lithologic and gas-bearing properties of sweet spot in tight sandstone reservoir. The high-quality sweet spot is characterized by the lower velocity ratio and Poisson impedance. Finally, the actual seismic data are selected to predict the sweet spots in tight sandstone gas reservoirs, so as to verify the validity of the rock physical simulation results. The significant consistency between the relative logging curves and inversion results in different wells implies that the utilization of well-bore rock physical simulation can guide the prediction of sweet spot in tight sandstone gas reservoirs.
Highlights
Conventional reservoirs remain a very important part of the world’s oil and gas supply, horizontal drilling and multistage fracturing have made it possible to exploit and develop unconventional reservoirs (Sharma and Chopra 2016)
The result shows that the mudstone, tight sandstone and water-bearing sandstone are mainly concentrated in the area with high velocity ratio and Poisson impedance, and the elastic property of sweet spot is characterized by low velocity ratio and Poisson impedance
Five rock models and three well-bore rock physical models are built after supposing parameters such as mineral components, porosity, pore-fluid type and saturation
Summary
Conventional reservoirs remain a very important part of the world’s oil and gas supply, horizontal drilling and multistage fracturing have made it possible to exploit and develop unconventional reservoirs (Sharma and Chopra 2016). Recent advances in pre-stack seismic data analysis show that some elastic parameters appear to be correlated with formation lithology, porosity and pore fluid (Sena et al 2011; Zhang et al 2012a, b). These parameters can yet be regarded as effective factors to predict sweet spots. The technologies of rock physics analysis and pre-stack elastic parameters inversion were perfectly combined to predict the sweet spot of tight sandstone reservoir in a case study
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