Method and apparatus for detecting hydrocarbons with NMR logs in wells drilled with oil-based muds

摘要

A method and system for estimating native hydrocarbons from oil-based drilling muds with the aid of NMR data. Adaptive echo stacking may be used to balance between precision and sensitivity to changes in the fluid composition. Apparent T₂ decay time and effective diffusion constants derived from the NMR data may be transformed into an indication of native hydrocarbon type, using known diffusion constants, fuzzy logic, and neural networks.