Construction of a diagenetic history and identification with quality ranking of reservoir flow units: Grayson field, Columbia County, Arkansas

The purpose of this study was to describe depositional and diagenetic characteristics of the (Jurassic) Smackover formation and subsequently identify and rank the quality of flow units within Grayson field, Columbia County, Arkansas. The field has production from the Smackover, a reservoir which consists mainly of highly altered peloidal grainstones. This was a four part study including a lithological analysis of ten cores, a petrographical study of 97 thin sections, a petrophysical study of reservoir properties from core analyses and borehole logs, and predictive mapping of quality ranked flow units across the field. Examination of the cores and thin sections revealed H1a as the main pore type in Grayson field, which was a hybrid of both depositional and diagenetic processes with dominantly interparticle pores. The lowest ranked reservoir quality corresponded to intraparticle and intercrystalline pore types, which occurred mainly in the wackestone/mudstone and packstone/wackestone facies. The highest ranked reservoir quality corresponded to the H1a pore type which occurred mainly in the grainestone/packstone facies 1 and 2. The reservoir quality maps identified the spatial distribution of the facies within the field, which could be used to locate zones for possible in-fill drilling. These results should aid in the economical development of Grayson field and other similar fields.