Drilling and Completing Multilateral Horizontal Wells in the Middle East

Abstract Multilateral completions provide unique systems that mechanically connect horizontal laterals to parent wellbores and allow selective or commingled production from the individual laterals. This paper will discuss the specific techniques used to drill and complete several multilateral horizontal wellbores in the Middle East. The discussion will focus on how the latest developments in drilling technology were employed to successfully drill the horizontal wellbores in the subject wells. Additionally, the completion systems used to permit control and access of the multiple wellbores in these wells will be presented. The paper will also review other developments in drilling technology that can facilitate success in applying this technology. This paper draws upon specific field case histories in the Middle East to demonstrate the techniques discussed and their economic benefits. Introduction The changing economics of oilfield development has resulted in operators, and therefore, service companies, being challenged to produce greater quantities of oil at reduced costs. Deeper and more corrosive environments are being produced to increase production capacities, and new technology is being encouraged in the attempt to generate as much "value" from a well as possible. This pursuit and the resulting development of new techniques has been a major factor in allowing projects to be attempted that traditionally would not have been viewed as economically feasible. The multilateral concept is a prime example of innovative technology that has been used to support current economic needs, and operators in the Middle-East have been among the pacesetters in the use of this concept. In 1996, it is estimated that over 35 multilaterals of various descriptions were drilled in the Middle-East. Actually, the multilateral well concept is not new, with the first recorded multilateral dating back to 1953 to a field in Russia, The value of the concept has always been recognized, but traditionally, the drawback to its use has been the completion techniques available and their capability to allow remedial work to be conducted. As we shall see, however, in the recent revisiting of this concept, these limitations have for the most part been overcome. In looking at the financial drivers of a multilateral well the unproductive (or vertical) part of the well is considered as "cost-driven," while the productive part of the well (the deviated or horizontal sections) would be considered as "value-driven." (Fig. 1) By definition. therefore, a multi-lateral well, especially if it is a re-entry, can be considered almost entirely as a "value-driven" process. Thus, the technology and processes that are available must be carefully evaluated to ensure that the maximum value will be generated from the horizontal laterals. Multilaterals can be broadly divided into two categories:Re-entries - where an existing well is re-entered, and multiple branches drilled off the existing wellbore.New developments - where a new well is drilled with the intention of completing as a multilateral of some type. Multilateral technology can now be used as a developmental concept for an entire field and can result in significant savings. For example, as can be seen in Fig. 2, a field that would normally be drilled with single deviated or even horizontal wells would require much larger platform facilities and require considerably more footage to be drilled when compared to a field developed with multilateral wellbores. Planning and Development of Design Concepts In planning a multilateral project. it is important that a multidisciplinary developmental team be employed for the initial planning stages. The team should include drilling engineers, reservoir engineers, geologists, and petrophysicists from the operator as well as multilateral (MLT) and completion specialists, directional drillers, and logging-while-drilling (LWD) specialists from the service company. P. 115^