A New Collaborative Workflow to Optimize Well Placement in the First Unconventional Horizontal Well in the United Arab Emirates

Abstract

Abstract A horizontal well was drilled in an unconventional source rock for the first time in the United Arab Emirates using advanced logging-while-drilling (LWD) high-resolution microresistivity and near-bit gamma ray imaging sensors. The well plan required locating a ±3 ft true vertical thickness (TVT) source rock sublayer; this sublayer was located within a giant undeveloped unconventional carbonate reservoir in a middle Cretaceous carbonate sequence onshore Abu Dhabi. Additional planning and drilling challenges included the absence of offset wells in this field and the associated structural geological uncertainty. Consequently, a vertical pilot hole was drilled to evaluate the local geological structure and to determine the reservoir properties. For source rock reservoirs, a unique and collaborative approach has been developed that enabled the associated specific challenges to be addressed. This approach was built on reservoir knowledge to help determine where and how to drill, as well as where and how to fracture, to optimize each stage of the field development. A well placement and geosteering methodology/workflow was developed and applied. This workflow used azimuthal high-resolution microresistivity and near-bit azimuthal gamma ray sensors to land and geosteer the well within the thin target layer, while maintaining the planned trajectory with minimum borehole tortuosity using real-time drilling optimization. The high-resolution microresistivity images were analyzed to classify image patterns to correlate to reservoir units for further field development and to better understand the reservoir flow units. The laterolog resistivities were also determined to be better suited for inferred Rt and Rxo measurements for petrophysical formation evaluation than the modeled electromagnetic wave resistivity inverted values. The well was successfully drilled, and the geosteering objectives were achieved with 100% reservoir contact. The field development strategy for the horizontal drain in the undeveloped source rock is being reviewed, based on these recent data, to benchmark and optimize well placement, formation evaluation, and production technologies, to evaluate the economic potential of this unconventional reservoir. This paper presents a case study after completing the first unconventional horizontal well in the UAE and describes the integration of fit-for-purpose geosteering technologies and optimized drilling performance to maximize reservoir contact and improve reservoir insight. Benchmarking of cost effective well placement and petrophysical data gathering requirements for the future field development program are also discussed for maximizing asset value.