1. School of Geosciences, China University of Petroleum(East china), Qingdao, Shandong 266580, China; 2. Key Laboratory of Deep Oil and Gas, China University of Petroleum(East china), Qingdao, Shandong 266580, China; 3. Geophysical Research Institute of Shengli Oil Field Company, SINOPEC, Dongying, Shandong 257022, China
Abstract：Brittleness is an important index to evaluate the fracturing ability of tight reservoir and is of great significance to oil and gas exploration and development. Due to the low exploration degree， large area and few exploration wells， it is difficult to describe and predict the brittleness of the dolomitic tight reservoir in the middle and lower part of Permian in the eastern Junggar basin. This paper carries out the prestack inversion and brittleness prediction of the reservoir by using the angle domain data， according to the petrophysics experiment. Prestack inversion includes the following methods. AVO inversion is applied to obtain the P+G and P×G attributes. Y（Young's modulus，E） P（Poisson's ratio，σ） D（density，ρ） and（L（λ）M（μ）R（ρ） inversions are applied to obtain the reflection coefficient of elastic parameters logging constrained inversion is utilized to get the actual value of multiple elastic parameters. Then， the brittleness is calculated with various characterization formulas， and its physical meaning and application effects are analyzed. The practical application shows that： ①There is a good fitting relationship between shear wave velocity and P-wave velocity in the study area， and Young's modulus and Poisson's ratio are distinguished from mudstone and non-mudstone. ②The dolomitic rock has the characteristic of high velocity， and the reservoir shows a double sweet spot structure. ③Using three small-angle data bodies to directly invert the reflection coefficient of elastic parameters， the YPD inversion method has a better reservoir identification effect and high resolution than LMR inversion. Especially in the density reflection coefficient data， obvious fan and channel alluvial features can be seen. ④There is a certain difference between the brittleness characterization results and the characteristics of elastic parameters. The favorable areas of the dolomitic rock characterized by brittleness are distributed in bands， while the elastic parameters basically distributed in continuous patches. ⑤ρE/σ is the best brittleness characterization formula in the study area， which can provide a reference for the prediction of brittleness in dolomitic tight reservoirs.
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