Regional porosity variation in Thamama-B reservoirs of Abu Dhabi

摘要

We present a large dataset of average porosity, depth, thickness and well locations for one of the Earth's major oil-bearing limestone reservoirs and discuss possible controlling factors. Petrologic data are not included in this study, but regional petrology data from earlier studies and detailed results from one representative oilfield provide a useful basis for interpretation of the present compilation. Porosity decreases with depth similar to porosity-depth trends from other limestone strata, but the main data cluster, representing the largest fields in the depth range 7000-9500 ft (2134-2896 m), follows a much steeper trend approximately parallel with the crest-flank trends of individual fields where crestal porosity has apparently been preserved by early arrival of oil. Maps of depth, porosity, thickness, and departure of porosity from the overall trend illustrate the geographic variation of these parameters. Solidity (thickness with porosity removed) is constant from crest to flanks in the largest fields, indicating that crest-flank porosity differentiation took place by closed-system compaction and cementation. The principal value created by this work is the framework established for focusing continuing studies that can further constrain the controlling processes and thus develop predictive tools for this particular reservoir and similar micropore-dominated limestones worldwide.