This study examined the stratigraphic architecture, depositional and diagenetic histories, and resulting reservoir characteristics that have influenced the occurrence, distribution, and quality of flow units in the Diamond M field, Scurry County, Texas. The study area is located in the Midland Basin. The field has production from the Canyon (Pennsylvanian) Horseshoe Atoll carbonate buildup. Recent drilling in the Diamond M field was done to evaluate ways to improve recovery by water flooding. Classification of depositional texture based on detailed petrologic and petrographic studies on three cores was done. Subsequent genetic classification of pore types by thin section petrography revealed three dominant pore types: intramatrix, moldic, and vuggy. The reservoir was zoned according to dominant pore type and log signatures to evaluate correlations at field scale by using neutron logs. Equations determined from core analyses provided equations used for estimating porosity and permeability, which were used to develop a ranking scheme for reservoir quality based on good, intermediate, and poor flow units at field scale. Ultimately slice maps of reservoir quality at a 10 ft interval for a 150 ft section of the Canyon Reef reservoir were developed. These reservoir quality maps will provide a useful tool for the design and implementation of accurate and profitable development programs.

Carbonate reservoirs may have a variety of porosity types created by depositional, diagenetic, and fracture processes. This leads to the formation of complex pore systems, and in turn creates heterogeneities in reservoir performance and quality. In carbonate reservoirs affected by diagenesis and fracturing, porosity and peremeability can be independent of depositional facies or formation boundaries; consequently, conventional reservoir characterization methods are unreliable for predicting reservoir flow characteristics. This thesis provides an integrated petrographic, stratigraphic, and petrophysical study of the 'Canyon Reef' reservoir, a Pennsylvanian phylloid algal mound complex in the Horseshoe atoll. Core descriptions on three full-diameter cores led to the identification of 5 distinct depositional facies based on fundamental rock properties and biota. Fifty-four thin sections taken from the core were described are pores were classified using the Humbolt modification of the Ahr porosity classification. In order to rank reservoir quality, flow units were established on the basis of combined porosity and permeability values from core analysis. A cut off criterion for porosity and permeability was established to separate good and poor flow units. Ultimately cross sections were created to show the spatial distribution of flow units in the field.