Local 3D understanding around horizontal wells provided by deep 2D azimuthal resistivity inversions

Success of horizontal infill wells targeting bypassed zones are challenged by uncertainties in the reservoir description but also by fluid content variation generated by differences in sweep efficiency over time. Optimizing well placement of such producer wells has a direct impact on cost and recovery where more marginal and complex targets are a natural consequence of increasing number of infill wells. This could, also, potentially unlock targets not accessible today with currently used methods and technologies. Innovative interpretation methods based on efficient measurements to map structure and fluids around high angle and horizontal wells while drilling are critical for future success in a marginal, but increasingly strategical, business on the Norwegian Continental Shelf.

This paper presents field case results of a new inversion method called 2D azimuthal inversions providing 2D azimuthal resistivity images in a plane transverse to the wellbore. This algorithm takes advantage of the full 3D sensitivities of ultra-deep directional resistivity measurements to map the 2D resistivity distribution in an imaging plane and find the dominant formation trends. Continuous deep azimuthal 2D imaging along the well path generates a 3D resistivity distribution in the proximity of the wellbore. Thus, for the first time resistivity distributions can be interpreted laterally to the well tens of meters from the wellbore. This is key information to update local 3D geomodels around the wellbore and to identify structural and potential flooding events laterally to the well. Sidetrack planning is another obvious application of this new inversion result that also will be presented in this paper.

The future challenge is to develop effective tools for updating local 3D geomodels during drilling to validate advanced interpretation based on 2D deep azimuthal inversions, as well as to quantify artefacts on 1D and 2D inversions produced by 3D effects. Operator and service companies need to work on effective workflows together to fully exploit the measurement potential for 3D mapping of geologic formations and fluids around the well.