Practicalities of 3D Well Placement

Well placement operations, in which ultra-deep electromagnetic (EM) tools are deployed have relied on 1D and 2D inversion algorithms, to generate geological models displaying the distribution of formation and fluid boundaries as defined by variations in resistivity above and below the well bore. Well placement optimization has focussed on changes to a wells TVD or inclination based on analysis of the resultant models. Where geology is complex, due to the depositional environment and post depositional deformation of the reservoir, in additional to vertical changes, there can be major lateral changes in the position of resistivity boundaries. In wells targeting these reservoirs, treating well optimization as simply an up/down problem severely limits the potential for successful well placement. Recent advances in inversion technology into 2.5D and 3D allow an assessment of this lateral resistivity variability. When deployed real time these tools introduce the option of azimuthal corrections to a well path in response to analysis of lateral changes in the EM field to optimize the wells position within the target reservoir. This presentation examines the practicalities of identifying changes in the position of formation/fluid boundaries in 3D and what needs to be considered when attempting well placement optimization under these circumstances.