Multilateral wells offer many benefits over conventional wells, including reduced overall drilling costs, lower environmental effect, increased total recovery, greater access to production intervals, and subsequently improved well production rates. However, it can be difficult to achieve a good quality casing window through which an additional lateral branch can be successfully drilled and completed. As bottomhole assemblies (BHAs) become more advanced, involving longer and stiffer strings of tools, and as completion design becomes more intricate, more attention must be given to the way the casing window is created because this is the foundation of multilateral well design. Track-guided milling systems have emerged as effective and accurate methods by which to control casing window geometry, and this paper will focus on recent advances in track-guided, precision window milling technology and its effect on multilateral well design. To avoid potential problems in running drilling assemblies or liner/completion strings, advanced milling technology should be used to create the casing window. During conventional milling, it is commonly difficult to control the action of the mill as it cuts through the casing; poor control creates a casing window that could, as a result of right hand rotation during milling, rolling-off to one side, leading to a skewed or shortened aperture. Uncontrolled and undefined window geometry introduces additional risks when re-entering a lateral wellbore, such as nonproductive time (NPT) and equipment damage. A good quality casing window, with precisely controlled length and width, helps ensure that drilling and completion equipment can exit the aperture without problems and facilitates repeatable re-entry access to both the mainbore and the laterals in future interventions. The quality of the casing window is just as critical in multilateral wells as in conventional sidetracking or whipstock operations. Advances in modern casing milling technology are pioneering improved multilateral well designs. Multilateral wellbore junctions can now be placed in deep, high-angle wells without compromising drilling or completion operations by using a track-guided milling system to create improved casing windows.
A major Abu Dhabi oil and gas producer targeted an increase in production from their major offshore oilfields. Better optimization of the reservoir through advanced well architecture was considered an option. One way to achieve this objective was through accessibility and hydraulic control of all horizontal drains. Multilateral technology is commonly used to increase the production per well and reduce drilling time while optimizing production facilities. The project targeted multiple reservoirs with two separate laterals to meet reservoir requirements. The application required individual through tubing access for intervention into each lateral. Multilateral technology has been traditionally limited to commingled production with limited or no access to the laterals. To help address and overcome these challenges, the operator planned and installed their first Level 5 multilateral tieback system (MLTBS).
To increase and optimize single well production performance, multilateral drilling and completion technology were implemented from a new single wellbore deep in the Tarim Desert of the Xinjiang Province in northwestern China.Although planning and preparation began in earnest in Tianjin months in advance of the actual installation, the on-site demands, distant logistics support, and the well depth operational demands of the project installation were the most challenging steps in the process. The remote location of the multilateral well in the Tarim Desert proved to be an operational and logistical challenge in terms of time (4-to 5-days travel time by vehicle) and distance (3600 kilometers) to the nearest repair and maintenance facilities in Tanggu, Tianjin Province in eastern China.The well design was based on a vertical pilot well, or motherbore, drilled and cased into the reservoir. The multilateral system was then installed to add another wellbore, thereby increasing reservoir exposure. The goals of this system were to accelerate production, increase ultimate recovery and, for this particular operator, qualify multilateral technology for application in this specific field. Because of the unprecedented depth of the proposed junction, thorough project management and planning were required throughout, from the feasibility phase through the execution phase, to mitigate risk and to promote a successful project installation.Strong collaboration between the operator and service supplier resulted in the world's deepest TAML Level 4 cemented multilateral installation at 5082 m TVD junction depth and 5889 m MD at the lateral toe. This was also the first multilateral installation by Tarim Oil Company and the first cemented Level 4 multilateral installation in China. This paper describes the objectives, challenges, best practices, contingencies, logistics issues, results, and lessons learned from the implementation of this deep-set multilateral technology.
An operator was challenged with increasing production efficiencies from new single wellbores in the deep Tarim basin reservoirs of China. To increase and optimize single well production performance, multilateral drilling and completion technology were implemented on this initial pilot test well. The remote location of the multilateral well in the Tarim Desert of the Xinjiang Province in northwestern China proved to be an operational and logistical challenge in terms of time (4 to 5 days travel by vehicle) and distance (3600 kilometers) to the nearest repair and maintenance facilities in Tanggu, Tianjin Province in eastern China. Critical planning, aggressive project management oversight, and strong collaboration between the operator and service supplier resulted in the world’s deepest TAML Level 4 cemented multilateral installation at 5082 m TVD junction depth and 5889 m MD at the lateral toe. The well design was based on a vertical pilot well, or motherbore, drilled and cased into the reservoir. The multilateral system was then installed to add an additional wellbore, thereby increasing reservoir exposure. The goals of this system were to accelerate production, increase ultimate recovery and, for this particular operator, to qualify multilateral technology for this particular field application. Because of the unprecedented depth of the proposed junction, thorough project management and planning were required throughout, from the feasibility phase through the execution phase, to amplify risk mitigation and to effect a successful project installation. This project is the first multilateral installation for this client; it was the first cemented Level 4 multilateral in China, and is the deepest Level 4 multilateral installed worldwide. This paper describes the objectives, challenges, best practices, contingencies, logistics issues, results, and lessons learned from the implementation of this deep-set multilateral technology.
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