Historically, the ability to perform intervention on multilateral wells has been limited. While multilateral (ML) well construction technologies have progressed to a high level of reliability, multilateral systems that enabled intervention during the life of well had a more limited track record. Intervention outcomes after prolonged periods of production were less consistent. This lack of technologies with sufficient intervention case histories meant that generally multilateral well architecture was not selected in applications where thru tubing intervention was a requirement. In recent years, multilateral well architecture has continued to increase in demand, with more ML wells drilled and completed in the last five years than any other five-year period in the technology's history. With this increased demand has come industry enthusiasm to further mature its intervention capabilities. This paper will review two recent case histories of separate multilateral well completion systems that enable intervention. This opens up new potential for the industry to take advantage of the cost reductions achieved with multilaterals in a much larger scope of well applications. Two separate completion systems will be covered in this paper, System A installed in a cemented multilateral junction and system B, a completion that creates a hydraulically isolated junction via either a dual string completion or a single string completion that splits into two strings. These case histories were exectuted in 2017 to 2019, and interventions were performed after one to two years of production. Detailed in each case study will be an overview of the equipment, the operational sequence, intervention outcome, and any lessons learned or improvements. The systems have demonstrated themselves as a reliable method to access laterals in non-ideal downhole environments where debris is present after the well has been on production. The tubing sizes for the case studies are 3-1/2" and 4-1/2". In each of these wells, the following operations have been successfully performed: drift testing, acid stimulation through coil tubing and breaking of a ceramic disc. Both slickline and coil tubing have been used for the interventions and in some cases with tractors. Junction inclinations range from 1 to 43 degrees. Plans for ongoing installations for the systems are being executed in the Middle East Region. Further, expansion of the system A capabilities by integrating it with other existing technologies is also planned. This will enable projects such as the installation of a trilateral well with flow control and intervention for each individual leg, and also the conversion of existing single bore wells to multilateral with intervention capability.

In the past, accessing laterals after a multipacker completion system installation in a multilateral well presented significant risks to drilling operations because certain crucial operations, such as acid stimulation, required a rig on location. Recently, a Middle East operator successfully installed an isolated multilateral completion system. The system was deployed in a well located in an onshore field in the Arabian Gulf region. The isolated multilateral system was customized for multilateral wells that require re-entry capability to access the lateral. The system provided a completion window equipped with landing profiles and sealbores that enable deflector settings for lateral access or isolation sleeves for lateral control. Additionally, a unique latch coupling allowed for installation at the optimum azimuth and depth of the system for lateral re-entry operations. Historically, in installations that required access to the lateral, a pilot hole had to be drilled and subsequently plugged and abandoned to avoid running a dual-packer completion, followed by running a single packer as an alternative to enable safe stimulation of the lateral. Using the new multilateral isolation system enabled the first combined observation and producer well with a dual-packer completion string. The well represented a technical milestone for the service company in the development of multiple reservoir fields. Using the isolated multilateral completion system allowed the operator to achieve the following results: Maintain accessibility to the observation bore for future monitoring and producing from the other laterals. Improve surface infrastructure by reducing the number of wells to be drilled. Save on drilling and completion costs with individual observation wells. Achieve accessibility through the completion on either lateral independently. Perform acid stimulation treatments using a rigless unit at any point during the life of the well through a multipacker completion. Risk reduction with drilling rigs because critical operations, such as acid stimulation and well testing, can be satisfactorily performed using a rigless unit instead of a rig on location. The identification of further benefits and lessons learned will be addressed in future work. In conclusion, the Middle East operator had achieved success in the deployment of newly acquired technology for the multilateral/single-bore completion with multipacker systems.