State-of-the-art modeling permeability of the heterogeneous carbonate oil reservoirs using robust computational approaches

Abstract

The current study is aimed at developing straightforward and robust models for permeability prediction in heterogeneous carbonate oil reservoirs. Two heuristic methods including Group Method of Data Handling (GMDH) and Gene Expression Programming (GEP) were utilized to model the formation permeability with respect to the static parameters including porosity, irreducible water saturation, and pore specific surface area. To do this, the required data points were assembled from the literature and were classified into the training and test data sets. After rigorous processing, two unique GMDH and GEP derived models were proposed for the first time for fulfilling the scope of this work. The validity of the new suggested models was examined by utilizing various statistical parameters integrated with visual analysis. Consequently, the results of the analysis reveal the high exactness of the aforementioned GMDH and GEP models by Average Absolute Relative Deviations (AARD%) of 37.15% and 16.55%, respectively. Implementing a comprehensive data and error assessment prove that GEP based model provides the most accurate forecast of permeability than all the available and generally published correlations for permeability. This is due to the fact that existing models are mainly developed for the sandstone reservoirs over a restricted range of parameters; whereas, the proposed tools are created for heterogeneous carbonate reservoirs over a comprehensive databank. The results of sensitivity analysis demonstrate the high impact value of irreducible water saturation and pore specific surface area on the modeling process. Moreover, the validity of the database and GEP modeling is verified by Williams’ method, in which about 95% of data are located in a valid region. To end with, reliable methods for permeability calculation as the most eminent feature of the porous media are proposed here, which can be integrated with simulators or any modeling study dealing with fluid flow in heterogeneous carbonate reservoirs.