The sector screening review is a surveillance tool used to assess and find opportunities to increase the oil production and improve the performance of the reservoir. We developed a novel interdisciplinary workflow (geology-engineering) integrating dynamic and static data in order to generate opportunities at well and field level; this methodology was used to analyze the impact of fractures in the reservoir performance and management. The complexity of the geology on areas near a graben system (structure at center of the field with biggest vertical displacement) was suspected to cause flow anomalies that ultimately affected the well productivity indexes. After an exhaustive evaluation, it was noticed that a well showed lower productivity index (PI), 2-3 times less than nearby producers in the area, same reservoir Unit Z2 (similar lengths, conditions). To understand the root cause of such performance, a geoengineering workflow was implemented, integrating pressure transient analyses (PTA), production logging (PLT), bottom hole image (BHI), seismic (exceptionally complete dataset) and extrapolated to other wells with similar behavior. The PLT showed that 70% of the well contribution was concentrated in only a small interval of the horizontal section, this interval was correlated to a conductive fault through BHI, which was also detected by seismic (correlates with low velocity anomaly). The PTA showed unexpected pressure transient behavior suspected to be related to the dynamic effect of the fault and associated fractures. Learnings from above analyses triggered actions in different scales/stages: at Well scale, 1st Stage: the well was selected to be completed using selective stimulation with abrasive jet, to remove damage of the first 400 ft. of the well (skin factor masked by fracture contribution) and unlock the potential of non-contributing zone (after fault, to toe); allowing the well to produce 25% additional oil and doubling the PI. 2nd Stage (planned): workover proposal to install lower completion (LC), to ensure even depletion, avoid by-passed oil and prevent early water/gas breakthrough. Field scale: new wells to be drilled in reservoir zones potentially affected by the graben will be equipped with LC. Finally, a geological well testing framework matching the PBU and PLT was implemented based on a high resolution geological model designed to capture the properties of the matrix and fractures. The results from this study were used as diagnostic tool for additional wells with similar conditions which lack PLT data. Noticeably, the presence of flow controlling fractures was usually suspected but not properly assessed/quantified in this reservoir, mainly due to the fact that the dynamic impact of these fractures was masked by the overlapping of different geological phenomena. The implementation of our geological-engineering workflow allowed immediately triggering actions that could lead to major performance enhancements at field- and well-level, including field development, management and modelling practices in such complex geological arquitectures.

The study presents the sequence stratigraphy of the carbonate platform focused in lower part of Shuaiba Formation, as well as the organization of the arrangement formed by the cyclical sedimentological evolution at high-resolution scale, through the facies analysis, diagenetical imprints and finally, significance of stable carbonate isotope results in the building up of carbonate platform in southeast Abu Dhabi. Interpreted stratigraphic surfaces from integration of depositional facies reviewed in all available cored data within studied area and stable carbon isotope results allowed that four small-scale regression-transgression depositional cycles can be discriminated which are stacked into a medium-scale sequence, that may record a 600 kyr Milankovitch signal. The small-scale sequences were correlated within the studied area using both conventional well logs and stable isotope records. Transgression hemicycles represent the increasing of accommodation space and can be identified in direct evidence, such as 25-40 ft. thickness of lithocodium/bacinella floatstones and skeletal peloidal packstones facies, association of facies interpreted within upper slope sub-environment. Likewise, in δ13C profiles, the rise/fall turnarounds of small-scale sequences are marked by negative δ13C peaks and associated with characteristics patterns: (1) proportion decrease of shallower sub-environments facies is interpreted as an rising relative sea-level and (2) decreasing δ13C trends interpreted to be related to decreasing nutrient supply. The medium/big pores of floatstones poorly connected in packstone matrix are expressed in the medium/high porosity with low permeabilities. In contrast, regressive hemicycles represent the reduction in accommodation space and can be characterized in direct evidence, such as the growing up of persistent 10-20 ft. thickness with thousands of meters of correlation of stromatoporoids and rudist facies, association of facies interpreted within shelf-margin complex sub-environment. In addition, the fall/rise turnarounds are marked by positive δ13C peaks, associated with the stromatoporoids/rudists mounds with characteristic patterns: (1) proportion increase of shallower sub-environments facies is interpreted as falling relative sea-level and increase in proximity and (2) increasing δ13C values interpreted to reflect increasing nutrient supply. Unusually very high permeability is attributed to the present of fractures and dissolution events that is enhanced where proportion of stromatoporoids facies are more pronounced. The described characterization resulted in the identification of genetic cycles that reproduce the sedimentological evolution, which are presented in small-scale sequences. In addition, the δ13C values enabled to understand the internal organization and the development of the carbonate building up in the Shuaiba shallow platform evolution. This study provides update and understanding on sedimentary facies, depositional pattern, and expands on previous published works, using new approach from semi-regional to local scales. Finally, results help to understand the laterally extensive water break-through thin intervals, which are directly related to the regressive hemicycles described previously.