Characterization method of heterogeneity for Chang 8 tight reservoir in Honghe oil field, southern margin of Ordos Basin

Abstract

Due to the complexity of accumulation conditions of Chang 8 tight reservoir in Honghe oil field, the southern margin of the Ordos Basin, the geological "sweet spots" are small and scattered, and the reservoir is remarkably heterogeneous. The Honghe 36 well block of the Honghe oil field was taken as an example in this paper, based on the main constrains for reservoir enrichment and production, three major heterogeneity characterizations, including reservoir quality, fractures and oil-enrichment, were carried out, and then combined with evaluation on productivity. A comprehensive characterization model for reservoir heterogeneity has been established, which can represent the geological characteristics of the reservoir. A classification standard for matrix reservoirs was established from the micro and macro scales to discuss the formation mechanism of reservoirs constrained by sedimentary and diagenetic factors. A characterization method for reservoir heterogeneity that "sedimentary elements constrained diagenetic facies, and diagenetic facies constrained reservoir quality" was proposed, which clarified the plane distribution of reservoirs. Based on the constrains of different grades of fracture zones on oil and gas enrichment, a multi-scale fracture zone classification scheme was established. Well logging and seismic data were combined to carry out hierarchical predictions to quantitatively characterize the multi-scale fracture zones from meter scale to kilometer scale. The oil-bearing capacity of wells was discussed, and combined with oil and water distribution pattern, an oil saturation field was established to quantitatively characterize oil-bearing heterogeneity. On this basis, three strong heterogeneity characterization results were superimposed to establish a comprehensive evaluation model for tight reservoir heterogeneity, which was used to clarify development target distribution.

Keywords

• reservoir quality
• multi-scale fracture
• oil-bearing capacity
• heterogeneity
• tight reservoir
• honghe oil field
• ordos basin