Fracture characterization in basement reservoirs through seismic attributes

R ecent efforts to understand fracture characterization, their density and numbers have increased signifi­cantly. With the introduction of novel technologies and methodologies of data preconditioning, decom­position, and attribute analyses, new workflows have been introduced to optimally determine and visualize effective fractured networks. In detailed seismic data analysis it is critical to determine the accurate location of effective fracture zones and their characterization as these may lead to high potential hydro­carbon exploration zones. Therefore we suggest a workflow to delineate and quantify effective fracture networks from seismic data. Our proposed methodology has been calibrated using all available surface and subsurface data that included testing results. The three core elements to this workflow are: fault network delineation, fracture density zones estimation, and effective fracture zones identification. These are then used to visualize the most potential regions in the area. Then through 3D volumetric representation of the blending results, one can quantify the amount of effective fractures per region and identify areas of interest. For a detailed description of the methodologies and workflows used to achieve the results, the reader is referred to (Aqrawi and Aqrawi, 2013) and (Alai et al., 2014). Here we showcase a sequential and systematic approach to delineate dense effec­tive fracture zones from seismic data. Only the seismic data is used to perform this analysis, and the well data is solely used for correlation and validation. The paper discusses the integration of the sequential steps of the proposed methodol­ogy that incorporate ‘consistent’ unsteered fault networks, detailed estimation of the fracture density and effective fractures zones and the geologic and structural setting of the studied area. Three datasets were obtained from the Malay basin, which has been formed as a pull-apart related to the development of the three pagoda right lateral fault. Open fractures within the Malay basin that originated by strike– slip tectonics strike NE-SW and ESE-WNW and oblique to major bounding faults of the studied areas. Wells drilled with trajectories parallel to the bounding faults intersected higher numbers of effective synthetic fracture networks with higher testing rates. From the first dataset, numerous well data have been integrated to validate the workflows and our results are supported by well testing data. Regarding the second and third case studies, the trajectories of the planned exploration wells have been validated. In addition, our results identify potential nearby areas where appraisal wells are recommended to test additional well-developed fracture networks.