Depositional Environments, Diagenesis, And Reservoir Delineation Of The FCU 1947 Upper Clear Fork Cored Interval - An SEM Image Analysis Approach To Pore System Characterization

Abstract

Delineating reservoir facies in heterogeneous tidal flat carbonates is a challenge which requires analysis at greater resolutions than wireline logs can provide. Such depositional environments are documented in the upper Clear Fork deposits of Fullerton Field in West Texas. This study examined lithofacies and depositional facies of core to gain understanding of the best reservoir facies. Whole-core examination, Core Laboratories and wireline log analysis, thin section microscopy and SEM image analysis were used to delineate reservoirs.Subtidal facies were deemed the poorest of reservoirs because compaction, anhydrite plugging, and burial diagenesis obliterated pore space. Intertidal facies were determined as the best reservoirs, particularly those directly beneath shallowing-upwards cycle tops. Grainier fabric and fabric selective dissolution of these facies increased porosity. Supratidal facies were determined as the second best reservoirs because eogenetic dolomitization protected them from compaction. Furthermore, these depositional facies can be correlated to nearby wells via distinct wireline signatures.