Rock physics modeling to assess the impact of spatial distribution pattern of pore fluid and clay contents on acoustic signatures of partially-saturated reservoirs

Abstract

The identification of pore fluid type, saturation and distribution pattern within the pore space is of great significance as several seismic and petrophysical properties of porous rocks vary largely by fluid type, saturation and fluid distribution pattern. With the help of rock physics modeling, the impact of fluid saturation as well as fluid distribution pattern on seismic velocities, acoustic impedances and seismic amplitudes is estimated on porous rock of early Cretaceous Mississauga sands. For this purpose two saturation patterns: uniform and patchy saturations are considered within the pore spaces. The primary goal of this study is to understand the vertical and horizontal trends of numerous seismic parameters such as P-wave velocity (V P ), S-wave velocity (V S ), their impedances, V P /V S ratio, bulk density (q b ), seismic reflectivity etc. as a function of fluid saturation, saturation pattern (patchy or homogeneous), porosity (/) and clay content. The results reveal that the seismic parameters and offset dependent amplitudes are very sensitive to pore fluid saturation and distribution patterns and physical properties. As the hydrocarbons (oil/gas) saturation increases, the compressional wave velocity decreases. P-wave velocity is 20-40 % higher in case of patchy saturation than of homogeneous saturation. Similarly, reservoir porosity and clay matrix control the elastic response of porous rock due to which seismic velocities decrease with increase in porosity and clay content.

Sweet spot prediction in tight sandstone reservoir based on well-bore rock physical simulation

“…The modulus and density of rock component are mostly measured in the laboratory, and the content can be supposed during the simulation process. According to the Mineral Handbook of Schlumberger and Ahmed et al (2016), parts of inputs are given in Table 1:…”

“…We have to admit that the method to determine the best indicator using well logs and rock test data is not suitable for the area with little or no wells, and the best indicator needs to be calibrated and tested for the local situation (Chen et al 2009). Seismic rock physical analysis is an important technique to establish the connection between reservoir elastic parameters and petro-physical properties in the research area with little and no wells (Mollajan et al 2015;Ahmed et al 2016;Ehsan et al 2016).…”

An Integrated Seismic Interpretation and Rock Physics Attribute Analysis for Pore Fluid Discrimination

“…Various techniques such as seismic attributes [4], amplitude versus offset analysis [5,6], rock physics modeling [7,8] are widely used to differentiate seismic response of reservoir rocks at various fluid saturation and fluid's nature. Rock physics modeling is used to interpret microscopic and macroscopic pore heterogeneities with much more accuracy [5,6,8].…”

“…Various techniques such as seismic attributes [4], amplitude versus offset analysis [5,6], rock physics modeling [7,8] are widely used to differentiate seismic response of reservoir rocks at various fluid saturation and fluid's nature. Rock physics modeling is used to interpret microscopic and macroscopic pore heterogeneities with much more accuracy [5,6,8]. In quantitative seismic interpretation and rock physics modeling of reservoir intervals, fluid substitution is an important part which provides a tool for fluid identification and quantification of reservoir fluids [5][6][7][8].…”

“…Rock physics modeling is used to interpret microscopic and macroscopic pore heterogeneities with much more accuracy [5,6,8]. In quantitative seismic interpretation and rock physics modeling of reservoir intervals, fluid substitution is an important part which provides a tool for fluid identification and quantification of reservoir fluids [5][6][7][8]. This is commonly performed by using wellknown Gassmann's equation [9].…”