Improving seismic calibration and geomechanical models through characterization of anisotropy using single and multi well data: Case Study in Forties Field, UK

Abstract

Extending the life of mature fields is dependant on reducing cost of operations (drilling & completions) and choosing locations for optimized production. Understanding the implications of anisotropy helps in reducing the uncertainty of wellbore stability models and improving seismic calibration. A major difficulty in extending seismic and sonic processing for geomechanical and geophysical applications within anisotropic media is the determination of an anisotropic velocity model. However, mature fields, where multiple wells are drilled at various deviations, represent optimum conditions for acquiring sonic data to determine anisotropy parameters. A case study is presented in the Forties Field, UK where the anisotropy parameters were studied at one well location from full waveform sonic logs, borehole seismic and core analysis. The field wide sonic data was then integrated with the single well results and used for a field wide calibration of the sonic data to account for the effects of anisotropy caused by the shale layering in the overburden. Subsequently, the wellbore stability predictions and seismic interpretation were updated and showed improvement by utilizing the anisotropy results.