The Role of Mechanical and Acoustic Anisotropies on Reservoir Characterization and Field Development in North American Fractured Unconventional Shale Reservoirs

摘要

The strong anisotropic characteristics of unconventional reservoirs and their seal formations impact the reservoir characterization and field development plans significantly. When the input parameters needed to run reservoir flow simulators and geomechanical models in these formations are obtained using isotropic assumptions and the associated in situ stress and direction dependences are not incorporated the prediction often compromise significant deyiation from the field observations. These-consequences in the modeling stages typically impact all major operations including drilling design and implementations, completion integrity and hydraulic fracturing design, fracture monitoring via surface and downhole microseismic monitoring for seal integrity and environmental impact minimization as well as long term depletion and seal integrity surveillance and risk assessment and sensitivity analysis. Ever since the drilling industry started to take on harsh environment drilling applications from drilling horizontal wells with multistage fracturing to unlock unconventional gas and oil resources to extended reach or multilaterals wells in complex geological environments such as sub-salt plays in the cases for remote ultra deepwater locations with high formation integrity issues, the role of formation anisotropy became substantial for economically viable and technically sound field development and production in these challenging environments. A comprehensive research study have been conducted using field data from several fractured gas and oil shale reservoirs in North America in order to study the impact of inclusion of anisotropic mechanical properties and strength on alteration of mechanical characteristic of the field. Seal shale formation data was also used to compare similarities and differences between seal and resource shale formations. Well logs, seismic, and drilling data, laboratory velocity and deformation anisotropy measurements have been evaluated with and without anisotropic rock property assumption to confirm the role of anisotropy in the changes, with the two assumptions.