Quantitative characterization of reservoir heterogeneity using the AHP-CRITIC method: A case study of the 2⁴ layer of E<italic>s</italic>₄^scx submember in Block Fan 151

Block Fan 151 is a low-permeability beach-bar sandstone reservoir with poor overall physical properties and strong heterogeneity, resulting in low oil recovery and a large amount of residual oil during its development. It is essential to analyze the influence of reservoir heterogeneity on the distribution of residual oil and identify its enrichment areas. Furthermore, calculating the reservoir heterogeneity comprehensive index plays a crucial role in quantitatively characterizing heterogeneity. Therefore, improving the accuracy of calculating the comprehensive index can provide a basis for predicting favorable areas for oilfield development and finding residual oil. ObjectiveTo improve the accuracy of the comprehensive reservoir heterogeneity index calculation, Methodsthis study proposes the analytic hierarchy process (AHP)-criteria importance though intercrieria correlation (CRITIC) combined weighting method. This method determines the composite weight of evaluation indicators using both subjective and objective data, overcoming the limitations of a single weighting method. ResultsQuantitative analysis of the reservoir heterogeneity of the 24 layer of Es4scx submember in Block Fan 151 shows that the heterogeneity composite index I ranges from 0.27 to 0.73, with approximately 63% of the values ranging from 0.4 to 0.65. The target formation in the study area shows moderate to strong heterogeneity, and the distribution of high values of the anisotropy composite index I aligns closely with the high-value areas on the residual oil saturation contour map. This indicates that the AHP-CRITIC combined weighting method can reasonably assign weights to the evaluation indicators and construct a quantitative evaluation standard for the reservoir heterogeneity of this layerConclusionThis approach provides a new method for the quantitative characterization of reservoir heterogeneity.