DIPMETER ANALYSIS BY A MONTE-CARLO TECHNIQUE

The dipmeter is a borehole tool that can be used to estimate the dip direction and magnitude of subsurface bedding. Typical computer dipmeter analysis utilizes crosscorrelation techniques which can be subject to cycle skipping. A Monte Carlo approach has been developed as an alternative dipmeter analysis method. The technique can process either raw or derivative dipmeter data and searches for the best-fit plane through a depth interval of the data. Operating on a parameterized forward model, this statistical, iterative algorithm randomly perturbs a local depth shift applied to a dipmeter trace. The algorithm then checks how well that perturbation fits the data by locally stacking the data interval. Random perturbations that degrade the solution are not necessarily rejected. Testing showed that only a narrow range of initial bad-guess acceptance-to-rejection ratios led to efficient global optimization. For synthetic and real dipmeter data, better results were achieved when processing differentiated dipmeter data than when processing raw dipmeter data. -from Authors