Calibrating Log Derived Stress Profiles in Anisotropic Shale Gas Formations- Incorporating Lab and Field's Measurements for Localized Model

The complex properties of the unconventional gas resources pose challenges to petrophysical evaluation techniques and tools. Data from standard logging tools and standard interpretation techniques produce high levels of uncertainties in the analysis, hence, limiting their reliability in producing thorough petrophysical solutions. Both tight and shale gas formations add multiple layers of complexity to the petrophysical evaluation with complex lithology and heterogeneity causing uncertainty in the hydrocarbon volume calculations and hydraulic fracturing completion designs. Without an accurate completions design, it would not be possible to produce at an economic rate or volume from these formations. Therefore, the need for accurate petrophysical and Geomechanical properties is critical for shale gas formations development. This paper provides field examples with workflow for identifying the anisotropy, calculating the log derived stress profiles and demonstrating the use of lab and field data for calibrating the log measurement. The lab measurements include the elastic moduli conversion dynamic (from logs) to static (from laboratory), stiffness tensors utilizing the oriented velocities in addition to rock strength and related parameters. This part includes the use of oriented velocities from the lab to validate and correct the existing tensors' correlations (Annie). Correcting the logging tool's measurement for factors such as the gas content and the acoustic conversion models will also be illustrated. The field data include the integration of the pre-fracturing job or mini fracturing to calibrate the calculated minimum horizontal stress (closure pressure) and post fracture analysis to validate the models. The result of these calibrations is a more accurate estimation of the formation stress profiles which improves the completion designs. Once these calibrations are done correctly, more accurate stress profile can be calculated in offset areas where cores or mini-fracturing measurements are unavailable. This paper shows the process for calibrating the log derived stress profile and goes through the components and uncertainty.