Placement of the multilateral junction is one of the most critical elements in the design of a multilateral well. A misplaced or mal-performing junction can have an adverse effect on an otherwise successful multilateral project. The optimum placement of the junction is a function of reservoir, geological, drilling, and completion criteria. The list may include such criteria as reservoir development strategy, pressures & heterogeneity, geological structure, lithology, wellbore stability, multilateral junction integrity, directional drilling requirements, logging requirements, artificial lift design, and completion type. These combined factors have a direct economic impact on the success and viability of the project. This paper describes a process whereby the proper junction selection criteria can be evaluated in light of pertinent technical and economic criteria and examines lessons learned from case histories with junction problems. Introduction A screening analysis is generally performed prior to having all of the data, offset information, and production information. Consequently, the purpose of this paper is to provide some Rules of Thumb meant primarily to narrow the focus area. Several assumptions are made in the generation of these Rules of Thumb:The beds are assumed to be laminar and horizontal for the base caseDogleg Severity (DLS) is a function of build rate and turn rate. In this paper, the 2D trajectory, where the DLS turn rate component is zero, is considered the base case.Correlations with respect to DLS and equipment capabilities are given with the assumption that the casing exit is from the vertical well.Directional tools, crossflow, formation damage, stimulation, and cleanup are design factors in all multilateral levels. However, discussion of optimal junction placement is primarily focused on TAML Levels 3–6. Levels 1 and 2 have junctions that are typically installed in the same horizontal plane in carbonates or very consolidated sands, where placement is not dependent on a correlation between the type of multilateral system and wellbore geometry. Conventional Well Design Criteria Many of the aspects that are discussed in this paper are not unique to multilateral wells. A cost/benefit analysis will always be performed prior to undertaking any oil field operation; therefore, many of the parameters mentioned are not pertinent just to multilateral well design alone. Issues such as placement of the wellbore in the reservoir, reservoir exposure length, completion and production types are all relevant to conventional well design. The "Morphing" of a Multilateral Well Multilateral wells metamorphose away from the process of conventional well design by creating more options. Instead of one reservoir entry point, it is possible to have two or more. Instead of one set of reservoir conditions, there may be two or more (including fluid types). Target geometries become more convoluted and 3-dimensional, and differences in approach and mindset come to bear with multilateral wells (Figure 1.). Issues Unique to Multilateral Wells The placement and construction of the multilateral junction are the key design differentiators between conventional and multilateral wells, and are the most critical elements in a successful multilateral well project.
Mature fields and new developments. Very different operating arenas but a common objective: produce hydrocarbons as quickly and efficiently as possible. The challenges for today's operators are many:complex geologic conditions such as compartmentalized or stacked reservoirsdifficult reservoir conditions such as viscous fluids or tight formationshostile environments, whether deep water or frontier development areasefficient and effective management of the reservoir development process. It is important now more than ever to look for new and innovative solutions to the problems and challenges facing us in all of these areas. Multilateral technology provides just such a solution. Multilateral technology has been successfully applied in all of these areas and has had a dramatic, step-change impact in the financial results of many. The ability to deliver an optimal reservoir development plan has been demonstrated time and again; and, in the process, new ideas in terms of equipment and reservoir development strategies have emerged. The adage of "if you can draw it we can drill it" is now more of a reality than it has ever been before. These new abilities allow for creativity to be released and for improved results to be achieved. However, in order to achieve these results, it is important to break loose of the old, self-imposed limits that have been placed on us and free ourselves from the bonds of technical restrictions. Knowledge is the key that can unlock those chains. Successful multilateral developments will be examined from around the world including the current multilateral hot spots of the South America, and the Deep Water of the North Sea. The impact of these advances on future field developments, both mature and new, will be examined in terms of operational accomplishments and economic success. This paper will also explore the potential of new, synergistic technologies and work processes and their impact on future field development strategies. The Impact of Multilateral Systems Multilaterals have the potential of being more than an evolutionary technology as horizontal drilling has been. Multilaterals are an evolutionary and revolutionary technology that could revamp the way we do business in the oil field. Petroleum Industry1 There have been notable successes in many areas in the world2,3,4,5. It is likely that, in the future, entire field management and development strategies can be affected by the proper implementation of multilateral technology. It is therefore important to understand the business drivers that affect our decisions. Evaluating the potential impact of multilateral technology can be very difficult because it incorporates facets from a series of broad and disparate functions. When an economic judgement on the viability of the project is made, it is easy to overlook factors that may contribute significantly to the financial results.6 These factors include:the reservoir characteristics and development plansproduction capabilitiesfacility capabilitiesavailability of current and future technologyexperience of the operator and the service companyquality of planning Multilateral wells have a marked bearing in all of these areas, and ignoring one or more areas could have a large effect on the overall financial success of a project.7 These areas can be grouped into three main categories:Well cost reductionReservoir value enhancementProject or facilities cost reduction
Over the last ten years there have been thousands of multilateral wells drilled in almost every energy market and geological basin of the world. During the same period wells that can be monitored downhole and flow controlled have increased in popularity and application. It is natural that these two technologies should meet and start a new family of wells known as "intelligent multilaterals."
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn the last two years, there has been a dramatic increase in the availability and complexity of multilateral systems. Many systems with new features and improved functionality have been introduced which have enhanced the application of multilateral technology. This system is among the latest of these offerings. This innovative system is a hybrid, TAML Level 5, that provides mechanical and hydraulic isolation at the created multilateral junction without cement, and re-entry capabilities into both the main and lateral well bores. This system also is very mechanically simple to run, utilizing a minimal number of trips to establish the junction and achieve mechanical and hydraulic isolation. Primarily designed for heavy oil applications where sand control is an issue, the system has potentially far reaching applications in this and other markets.The paper will describe the mechanical and operational functionality of the system and its' potential applications. Results of bench and field tests will also be documented and analyzed.
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