Paving the Road to Success: The First Advanced Through-Drill Pipe Formation Evaluation Run in the UAE to Appraise the Early Jurassic Reservoir Sequence

Abstract The Middle-Lower Jurassic carbonate formations, Offshore Abu Dhabi represent regressive cycles of sedimentation and are considered the key hydrocarbon-bearing formations, currently at a mature stage. On the other hand, the Early-Middle Jurassic reservoirs are still in the appraisal phase. In this paper we present the state-of-the-art formation evaluation planning, acquisition, interpretation, and the significance of the data integration to support efficient, well-informed decision making for the asset team during the operations and for the reservoir appraisal process. Previous experiences in offset analogues in the field were based on wellbores drilled faster through the early Jurassic sequence, targeting the deeper Triassic ones. This led to enlarged and highly rugose boreholes, highly affecting the basic well logs resulting in uncertain interpretations. In the first phase of the well subject to this study, a dedicated wellbore was designed to ensure extensive data gathering including advanced well logging, formation testing and coring for confirmation of the lithology, texture, structural aspect. However, the complex well trajectory (S-shaped) increased the risk associated with deployment of the conventional nuclear logging services, besides the wellbore instability and unexpected pressure regimes that heightened the risk data quality and differential tool sticking. The Advanced, through-drill pipe conveyance logging (ATDPCL) was used to mitigate these operational risks, ensuring safe deployment of a slim Quad-Combo tool string to evaluate the desired target reservoir units. The multimineral volumetric analysis was carried out using the (ATDPCL) data. The results showed a correlatable porosity development with sequence stratigraphy and the offsets. The elemental spectroscopy logging data has been incorporated to refine the model, and the hydrocarbon saturation has been evaluated. Mud logging data has been incorporated for calibration and consolidation of the results. Articulating on its high resolution, the simultaneously acquired acoustic and resistivity borehole images have been utilized to interpret the structural events and the wellbore breakouts, in addition to the good-gauged borehole as a first achievement in this dedicated drain, after the coring operations. Finally, the formation pressure testing and fluid sampling stations confirmed the fluid saturations and flow capacity, in addition to the formations pressure. The first-time deployment of the (ATDPCL) technology resulted in the proper evaluation of the Early-Middle Jurassic sequence, Offshore Abu Dhabi, paving the way to the future development of the appraised formations, adding more hydrocarbon into the asset portfolio. The multiple technology deployment options are seen to offer a flexibility to safely conduct the well logging operations in a range of well environments, enhancing the operational efficiency, eliminating the associated environmental risks with the radioactive tools deployment, and saving rig time.