ABSTRACT

Recent advancement in drilling practices allows the drilling of complex trajectories like horizontals, snake profiles etc. With this came the concept of having a more robust pre-drill mud window planning. The concept of Mechanical Earth Modeling (MEM) is a leap change in resolving the mud window uncertainty by running a well-bore stability model (WBS) considering all the three stresses and rock mechanical properties. Correct estimation of horizontal stress magnitudes, regime and direction play a critical role in such models. However, correlations established in the past had a lot of uncertainty associated with estimating these stress magnitudes.

Borehole acoustics tools currently available in the industry are capable of recording axial, radial and azimuthal waveforms, thereby characterizing near wellbore as well as the far field. Stress concentrations around the borehole leads to radial shear slowness variation. Estimation of stress magnitudes is possible by modeling of stress-sensitivity to acoustic waves in the anisotropic sand bodies. Multi-arm caliper and image analysis yields information about stress regime and direction.

This paper showcases the successful characterization of stress regime, magnitudes and direction, using the Integrated Stress Analysis approach, utilizing the acoustics, image and caliper data and later validated using the independent stress-test data. Derived horizontal stress magnitudes can be used to calibrate log-based horizontal stresses obtained from poro-elastic horizontal strain model. Realistic stress characterization will help in mitigating well-bore stability issues, cap-rock integrity study, completion design, sand production prediction etc. A unique amalgamation of advanced acoustic, image and formation testing workflows has been demonstrated, opening new ways of collaboration between several forms of formation logs and data for accurate and detailed horizontal stress characterization. This paves way for reliable estimation the maximum horizontal stress magnitudes, which otherwise remains a challenge in the industry.

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