Abstract

The unconventional Bahrah project aims to exploit the deep mid-cretaceous tight carbonate formation, which is prolifically hydrocarbon saturated, but with unsustainable productivity. Because of a challenging reservoir and large variations in heterogeneity, openhole horizontal wells with unique completion techniques were deployed with multistage acid fracturing within their lateral sections, with minimum rig time and a high degree of accuracy. From an operational standpoint, exploiting these limestone layers with this method means that more fracture initiation points can be achieved across the heterogeneous lateral and the size of the treatments is ideal for multiple applications in a shorter period, helping boost and sustain production.

Due to the unconventional reservoir nature of this field, optimizing fracturing stages and perforation cluster placement distribution becomes key to the approach. A holistic acid-based fracturing service was introduced that integrated two components—a completion suite with fit-for-purpose swellable packers to segment the annulus coupled with sliding sleeve devices in the liner that deploy ball-drop isolation and perform each fracturing treatment to a newly exposed zone. The technology is based on distribution of intelligent packers along the lateral section to develop the fracturing stages. Intelligent packers and their ports are placed based on the formation's petrophysical and mechanical properties to increase the cumulative production in a shorter timeframe. Acid fracturing using an enhanced diverter-based technique is then employed for improved individual stage targeting.

By combining these two processes into one continuous operation, the use of wireline for perforating and plug setting is eliminated, making the new multistage technology economical for these unconventional wells. Additionally, with coiled tubing-conveyed shift tools, the sleeve devices can be operated later in one run for any re-stimulation opportunity. The operator is forced to address the unique challenges of well operations, formation technical difficulties, high-stakes economics, and untapped potential from these layers. This has required an advanced and holistic fracturing technology, first of its kind in this field, to be applied. The completion and stimulation systems not only saved significant rig time to complete the well with long multilayer intervals, but also significantly helped reduce expenditures by standardizing design, simplifying the key operational stimulation complexity, enhancing system reliability. This well and completion design allowed for fracturing efficiency improving overall quality, health, safety, and environment performance for this project.

To date, more than 300 treatment stages have been successfully pumped. As more treatments are executed and experience is gained, stimulation design is optimized and productivity target identification is improved, providing further value to the operator. Finally, the lessons learned from a project-management viewpoint are also examined, discussing streamlining operations and addressing stimulation development. The technical and operational learnings during this project can serve as a best practice in other fields where similar challenges are encountered.

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