Publications

Formation fluid identification is a crucial component of reservoir characterization. This can be challenging in an environment where differentiating oil versus oil-based mud (OBM) filtrate or formation water versus water-based mud filtrate is driven by the absence of some sensors. Pumpout, as a part of the formation testing sequence, is used to analyze the reservoir fluid’s physical properties, however, similar to other log interpretations, the interpretation of the fluid analyzer’s sensor readings could create ambiguities, necessitating positive identification. Formation permeability, pumpout time, and operational risks all require positive fluid identification. Typically, the reservoir fluid type should be objectively determined as quickly as possible to help reduce operational costs and uncertainties in exploration wells. To address fluid analysis challenges in an OBM environment, a fluid scoring system was established to categorize fluids according to pumpout behavior and sensor readings. Several criteria were used to classify fluid type, including fluid density, capacitance, resistivity, compressibility, mobility trend, and pumping pressure trend. During analysis, all criteria are scored according to the confidence level of each sensor, and the summation of the score is used to determine the fluid type. The methodology and rationale of this approach for OBM systems have been validated through successful implementation across multiple fields and formations in Indonesia. The scoring system has been tested with actual data from more than 500 fluid analyses with 96% accuracy. This field-tested system is a simple, yet powerful, tool for objectively evaluating fluid type during real-time operations.