余目油田におけるレザバー•キャラクタライゼイション (その2)

TLDR: In this paper, the relationship between acoustic impedance (velocity) and rock properties such as porosity and clay content was analyzed in the reservoir interval based on the results of well log data analysis.

Abstract: Predicting the reservoir rock properties such as porosity and clay content is essential for estimating reserves and planning the optimum development of oil and gas fields. Modern seismic data, especially 3-D seismic data, has played an important role in reservoir characterization. A study has been performed to predict the reservoir disrtibution and the rock properties using 3-D seismic data in the Amarume oil field. The reservoirs are mainly in Kitamata Formation of Miocene which is considered to be deep-sea sediment gravity flow deposits. Several sandstone layers, which are discontinuous in horizontal direction, bear hydrocarbons. Productive sandstone reservoirs lie approximately 900m below the surface and vary from 5m to 20m in thickness. 3-D seismic survey area is about 2km in East-West direction and 1km in North-South direction. Acoustic impedance was derived from the 3-D data volume by seismic inversion method. Such impedance data can be related to rock properties and physical conditions in the reservoirs. The relationship between acoustic impedance (velocity) and rock properties such as porosity and clay content was analyzed in the reservoir interval based on the results of well log data analysis. An empirical equation was obtained by linear regression analysis to effective porosity versus acoustic impedance with a correlation coefficient of 0.87. The correlation was improved by addition of a clay, shale or tuff content term in the linear regression analysis. These relationships indicate that an increase in clay or shale content rises P-wave velocity. This observation differs from that quoted by several other investigators. Seismically derived acoustic impedance (I) was converted to effective porosity (φ) using the equation [I=5.72-8.15φ]. Depth structures, effective porosity and effective porosity-thickness of the reservoirs were mapped based on the converted effective porosity. The results were consistent with well data. 3-D seismic data can be a powerful tool for predicting the areal distribution of reservoir rock properties.