Reservoir-scale heterogeneity in depositional packages and diagenetic patterns on a reef-rimmed platform, upper Miocene, Mallorca, Spain

Predictive models for interwell-scale variations in heterogeneous carbonate rock are best made from outcrop studies of well-exposed limestone and dolo mite, such as the upper Miocene reef complex that crops out in the sea clif fs of Mallorca, Spain. The sea-cliff sections reveal highly complex lithofa cies stacking patterns that could lead to ambiguous Lateral correlations of coeval units. The stratigraphic complexity and distribution of primary and secondary porosity are the result of a sealevel-driven hierarchical stacki ng of different magnitudes of accretional units. Thickest sections of porous and permeable rocks are in the aggradational po rtions of the reef, upper slope, and outer lagoon units. The relative volum e of the various accretional units and heterogeneity in the lithofacies arc hitecture were dependent on the amount of carbonate production, which was r elated to (1) accommodation changes controlled by sealevel fluctuations and (2) depositional profile. Moldic porosity, mostly from the dissolution of aragonitic constituents, is the predominant porosity type, and its heterogeneous distribution is relat ed to the lateral and vertical distribution of lithofacies. The secondary p orosity in much of this reef complex was produced mainly during early dolom itization. Dolomite patterns are complicated, apparently mainly related to shallow flooding of the platform during third- or fourth-order sea level hi ghs and to geographic location of permeable pathways for brine reflux, prob ably primarily through fourth-order aggradational reef units. Many of these stratigraphic complexities and diagenetic patterns are below the resolution of seismic and well analyses; thus models based on outcrop d ata such as this can enhance reservoir development in certain shallow-water carbonate rocks.