In the past, junction construction technology has driven the design of multilateral wells. This practice has led to technical successes that may or may not have met all of the operator's desired well objectives. These projects have often been regarded as less than successful from an economic point of view. This regard is partly due to the way that junction construction has been viewed. Junctions are presently classified by looking at the technical differences in how they are constructed, such as TAML levels (Technology Advancement - Multi Laterals)1. Although this method is suitable for looking at junction construction complexity, it does not address directly what the junction does in service. Another approach would be to drive the design using information about reservoir/production requirements. Looking at functional groups of junction features will allow the drilling or completions engineer to make sense of the myriad of available junction systems. This technique can help optimize the multilateral junction type selection for a given project. The process of planning multilateral projects from conception through well design will be discussed with a focus on using a functional classification map to clarify the junction requirements. The Functional Classification Method will assist engineers in comparing equipment options. This comparison is accomplished by, first, defining the reservoir and economic drivers, and, then, by selecting the appropriate junction attributes. Furthermore, the method will provide a process for assembling the data required to prepare the final well design and to prepare precise tender documents. To illustrate this method, recent examples from the Middle East will be presented. Introduction Historically, drilling engineers have struggled to design a well that would accommodate a given multi-lateral completion while meeting all of the reservoir depletion requirements. As a result, there have been a number of failures when attempting to install these systems. Looking at multi-lateral technology and its real function in the oil industry, it becomes apparent that it is not a drilling tool at all. Instead, it is a reservoir depletion tool. Shifting the ownership of this technology provides an opportunity to see the planning process in a new light. The concept of multi-lateral drilling is essentially one of reservoir depletion economics. It is one answer to the question of how to get the most production for the lowest cost. By starting the planning effort in the reservoir camp, the equipment selection process is enhanced. Only after the reservoir mechanics are considered and the depletion requirements defined, can an unbiased judgment be made regarding equipment selection. To aid in this selection, an optimized multilateral planning process was developed. The process map will guide the engineer to a number of junction attributes that can then be used to select and compare various vendor systems. In the event that no systems perfectly match the required attributes, the information can be used as the basis for a compromise. If no compromise is sufficient, this process will provide the basis for tendering a request to design/build the required system2. All desired outcomes from a drilled well fit in one of two categories: to obtain information or to promote hydrocarbon retrieval. No matter what the multilateral well design, or which equipment is used in the well, multilateral technology's only purpose is to do these things more effectively or more economically. The challenge is to provide only the functionality that is essential to meeting the minimum well requirements. Then functionality that is desired but not necessary can be evaluated on a cost-benefit basis prior to acceptance to the well plan.

The benefits of drilling multilateral wells in slot limited applicationssuch as offshore platforms are well known. Using multilateral technology in aproject can minimize facility costs, reduce drilling costs, maximize reservoirexposure and reach secondary targets. When a project is in the planning stage, there is often resistance to multilateral concepts due to a perception ofincreased operational risks and doubts that the economic benefits will be fullyrealized. The key to broadening the implementation of this technology ismatching actual opportunities with robust, reliable multilateral systems. In a project in the Arabian Gulf, an operator implemented the use ofTechnical Committee for the Advancement of Multi Laterals (TAML) level 5pressure isolated junction systems with through tubing access to develop asingle reservoir in a slot limited application. Both pre-milled and retrievableoriented milled window technology were used as a platform for the completedjunction. This illuminates how this technology is used in new or existingwells. A study of how the unique operational issues were solved illuminates thesuccess of the application of this technology to this project. It will alsoprovide an insight into best practices to aid in the planning and execution ofother complex well types. Operational and economic results, as compared tosingle lateral wells on the same platform, provide insight into many advantagesrealized in this program. Introduction The prevailing reservoir management philosophy in Saudi Arabia is tomaximize reservoir exposure in each well. This is projected to increase theproductivity of each well or drilling slot. This will also reduce well problemsthat are exacerbated by high draw down such as coning or cresting, solidsproduction, or wellbore stability. Multilateral technology can assist in theapplication of this philosophy in several ways such as: Adding more footagethrough the addition of laterals, increasing the drainage area by covering moreareal extent with laterals, and making the drilled footage more productive byadding flow control and remedial capabilities to the well. In a field development the Arabian gulf, the primary zone of development atthis time is a sandstone, though several other zones are indicated in thearea. Ongoing reservoir management considerations suggested that multilateralwells would accelerate production from the eastern flank of the field. The project team was challenged with maximizing reservoir drainage from theplatform. To achieve this plan, medium reach horizontal wells along withmultilateral legs were evaluated in the reservoir model. Although all of thewells on the platform were indicated as potential for applying multilateraltechnology, only the last two were planned due to expected delivery time forthe equipment. A sub-team from the Marjan project team was formed with thefollowing objectives:Technically evaluate the drilling and completion equipment on the market forre-accessible drilling junctions.Determine the available completion alternatives.Evaluate full cycle operations and costs (drilling, completion, workover andproduction) to evaluate the long term operating/workover cost of the well.Evaluate the applicability of this technology to other areas within SaudiArabia.