TX 75083-3836, U.S.A., fax 01-972-952-9435.
AbstractThe drilling industry is turning from the use of oil-based mud to environmentally sensitive water-based mud systems. However, highly conductive water-based mud tends to limit the effective dynamic range of induction instruments, such as the multi-component induction well logging tool (3DEX SM ).To illustrate the influence of the conductive borehole and invasion on the 3DEX logs, we performed theoretical simulations for a simple 2-D formation model.To expand the operational range of the 3DEX technology in a water-based mud environment, we propose logging the 3DEX tool in combination with galvanic tools (Dual Laterolog, DLL and Micro Laterolog, MLL, or array lateral log, HDLL, and MLL) and apply the following sequential data interpretation procedure:(1) Determine the formation resistivity structure of the near wellbore environment and the horizontal resistivity of the uncontaminated zone using the galvanic measurements,(2) Determine the vertical resistivity and formation resistivity anisotropy of the uncontaminated zone using the results of the previous step and the deep 3DEX measurements.Evaluation of this technology on a series of synthetic models allows us to outline the expanded 3DEX operational environment. The presented field example validates the technology.The conclusion is that the combination of galvanic and induction measurements along with an inversion-based data interpretation method can effectively extend the dynamic range of the 3DEX technology, allowing the use of this technology in wells drilled with conductive water-based mud systems.