Direct extraction of fractured reservoirs' parameters based on five-dimensional data
ZHANG Hongxue1,2, YIN Xingyao2, LI Kun2, XU Xiaokai1
1. SINOPEC Matrix Corporation, Qingdao, Shandong 266071, China; 2. School of Geosciences, China University of Petroleum (East China), Qingdao, Shandong 266580, China
Abstract:The existing fluid identification methods for fractured reservoirs do not consider the influence of rock skeleton, fractures, pores, and oil-gas coupling in determining sensitive parameters of the fluid and fail to fully excavate fluid information contained in a wealth of azimuth information in five-dimensional (5D) data. In addition, oil and gas identification of fractured reservoirs is mainly based on indirectly calculated parameters. The inversion of wide-azimuth 5D seismic data has problems of ill-conditioned solution and uncertainty, and simulta-neous inversion of multiple fracture parameters is more likely to make the inversion accuracy of reservoirs' parameters decrease. Therefore, the fluid factors based on indirect algebraic combination inevitably accumulate calculation errors during calculation, which thus affects the effect of oil and gas identification. In view of the above problems, by combining the anisotropic Gassmann theory of pore elasticity and linear sliding theory, a new P-wave reflection coefficient equation directly characterized by the fluid factor decoupled by solid-fluid-fractures is derived. Moreover, the applicable condition and the sensitivity of the equation are analyzed. On this basis, the seismic inversion objective function with Bayesian framework is constructed, and the fluid identification method by 5D data is studied based on the time-frequency data, which thus directly obtains the fluid factor decoupled by solid-fluid-fractures in fractured reservoirs, eliminates the influence of cumulative errors, and improves the prediction accuracy. Research on models and actual data show that the proposed method can reasonably and reliably predict the distribution of oil and gas in fractured reservoirs.
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