Successful Applications of Azimuthal Propagation Resistivity for Optimum Well Placement and Reservoir Characterization While Drilling

We illustrate the use of a new technology for navigating and characterizing various types of oil reservoirs. Real-time images from Azimuthal Propagation Resistivity measurements provide a "map" of the resistivity patterns up to several meters around the wellbore. In addition, recently developed processing and quantitative interpretation techniques help guide the placement of the well and provide a new perspective of the formation. When navigating in gas drive reservoirs, the azimuthal resistivity measurement is used to maintain the wellbore at a prescribed distance above the oil-water contact. With its exponential sensitivity to distance, the measurement is able to detect even small changes in the distance to the oil-water interface. In a few instances, the azimuthal information provided by the real-time deep resistivity images indicates probable coning due to offset well production. Similar principles are applied in high angle drilling of water drive reservoirs. The deep azimuthal information allows the drilling engineer to maintain the wellbore at a prescribed distance immediately below a shale roof. The deep resistivity image from the azimuthal resistivity measurement also makes it easy to distinguish the roof from the occasional approaching shale lens. Whereas shallower reading LWD image logs (e.g. Gamma Ray and Density) only indicate a geological feature proximal to wellbore, the deep reading azimuthal resistivity measurement can provide geologic structure information at the reservoir scale. Visual displays show the subsurface surrounding the wellbore; quantitative algorithms accurately compute the distance, direction, and apparent dip for reservoir related geological events. A new conductivity unit named "Transverse Siemens" is proposed to help quantify the new azimuthal propagation measurement.