Abstract
There are abundant fracture cave reservoirs wrapped in Ordovician tight limestone in the Tarim Basin, with an average buried depth of 7000m. The connectivity analysis of fracture-porous systems and hydrocarbon-bearing analysis has essential roles in the deployment of high-efficiency wells of the Ordovician carbonate reservoirs in the Tazhong and Tabei areas of Tarim Basin, as they are the major targets for increasing production. However, in the previous researches, the pre-stack fractures’ prediction and the oil/gas detection results using conventional processing data were lack of accuracy, which failed to complete the need of high-precision exploration and development. Firstly, the paper systematically analyzes the characteristics of azimuthal anisotropy analysis using conventional processing seismic data. Then it explains the process of selecting data, which is capable to meticulous reflect anisotropy characteristics of the formation and contains uniformed coverage to improve convergent results of elliptical fitting. Finally, the paper focuses on the three steps of operating azimuthal anisotropic pre-stack fracture detection using common reflection angle gather and receiving a reliable result. Practice demonstrates that using common reflection angle gathers during research of fractures in carbonate rock has a distinctive effect, which can provide a decisive basis for the layout of high-efficiency well groups in the development block.
Highlights
The Ordovician carbonate reservoirs are developed in Tabei area of Tarim Basin and are deep buried with strong inhomogeneity [1, 2]
Through the application of fracture prediction based on the common reflection angle gather has a satisfying outcome
During the connectivity static engrave of large-scale fracture-cavity unit; its assistance restricts the scale of possible connective and fracture-cavity unit. It provides a more reliable connectivity analysis result in order to support efficient well location deployment and development of reservoirs
Summary
The Ordovician carbonate reservoirs are developed in Tabei area of Tarim Basin and are deep buried (about 7000 m) with strong inhomogeneity [1, 2]. Based on Thomsen, seismic attributes such as azimuth amplitude, azimuth velocity, azimuth AVO/FVO gradient and azimuth frequency are sensitive to fractures. He advised that the density of fractures can be calibrated. Because each point in the data has its own offset and azimuth, the OVT coil gather is more conducive for azimuthal-anisotropy fracture detection. Because the lack of azimuth and offset information, prediction results are inaccurate and hard to satisfy the development and production of carbonate fracture-porous
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